diff --git a/Makefile b/Makefile
index 9d76114..68b4f8d 100644
--- a/Makefile
+++ b/Makefile
@@ -23,19 +23,25 @@ $(BUILDDIR)/bios.bin: bios.asm tape.asm $(BUILDDIR)/memory.inc
 basic:
 	$(MAKE) -C apps/basic $(or $(MAKECMDGOALS),all) --no-print-directory
 
+sn76489:
+	$(MAKE) -C apps/sn76489 $(or $(MAKECMDGOALS),all) --no-print-directory
+
 $(BUILDDIR)/memory.inc: memory.mk
 	@mkdir -p $(@D)
 	@awk 'BEGIN { print "; Generated from rom_layout.mk; do not edit." } \
 		/^[A-Z][A-Z0-9_]*[[:space:]]*:=[[:space:]]*/ { print $$1 " .equ " $$3 }' $< > $@
 
-$(BUILDDIR)/rom.bin: $(BUILDDIR)/bios.bin basic
+$(BUILDDIR)/rom.bin: $(BUILDDIR)/bios.bin basic sn76489
 	echo "bios:   $(shell wc -c < $(BUILDDIR)/bios.bin) / $$(($(BIOS_ROM_SIZE)+0))"
 	echo "basic:  $(shell wc -c < $(BUILDDIR)/basic.bin) / $$(($(BASIC_ROM_SIZE)+0))"
+	echo "sn76489:  $(shell wc -c < $(BUILDDIR)/sn76489.bin) / $$(($(SN76489_ROM_SIZE)+0))"
 	objcopy --pad-to=$$(($(BIOS_ROM_START)+$(BIOS_ROM_SIZE))) \
 		-I binary $(BUILDDIR)/bios.bin -O binary $(BUILDDIR)/bios_padded.bin
 	objcopy --pad-to=$(BASIC_ROM_SIZE) \
 		-I binary $(BUILDDIR)/basic.bin -O binary $(BUILDDIR)/basic_padded.bin
-	cat $(BUILDDIR)/bios_padded.bin $(BUILDDIR)/basic_padded.bin > $(BUILDDIR)/rom.bin
+	objcopy --pad-to=$(SN76489_ROM_SIZE) \
+		-I binary $(BUILDDIR)/sn76489.bin -O binary $(BUILDDIR)/sn76489_padded.bin
+	cat $(BUILDDIR)/bios_padded.bin $(BUILDDIR)/basic_padded.bin $(BUILDDIR)/sn76489_padded.bin > $(BUILDDIR)/rom.bin
 
 
-.PHONY: $(TOPTARGETS) $(SUBDIRS) basic
+.PHONY: $(TOPTARGETS) $(SUBDIRS) basic sn76489
diff --git a/apps/sn76489/Makefile b/apps/sn76489/Makefile
new file mode 100644
index 0000000..b431d75
--- /dev/null
+++ b/apps/sn76489/Makefile
@@ -0,0 +1,22 @@
+.SILENT:
+ASM                     := zasm
+ASMFLAGS                := -w -b
+BUILDDIR                := ../../build
+
+TOPTARGETS              := all clean
+$(TOPTARGETS): $(SUBDIRS)
+
+all: $(BUILDDIR) $(BUILDDIR)/sn76489.bin
+
+clean:
+	rm -rf $(BUILDDIR)
+
+$(BUILDDIR):
+	mkdir -p $(BUILDDIR)
+
+$(BUILDDIR)/sn76489.bin: main.asm psglib_zasm.asm $(BUILDDIR)/memory.inc
+	echo '>$<'
+	$(ASM) $(ASMFLAGS) $< $@
+
+.PHONY: $(TOPTARGETS) $(SUBDIRS)
+
diff --git a/apps/sn76489/main.asm b/apps/sn76489/main.asm
new file mode 100644
index 0000000..3e2e49d
--- /dev/null
+++ b/apps/sn76489/main.asm
@@ -0,0 +1,89 @@
+#include "../../build/memory.inc"
+#include "../../bios.inc"
+#include "../../hardware.inc"
+
+CTC_BASE        .equ 020h
+CTC_CHANNEL_0   .equ CTC_BASE+000h
+CTC_CHANNEL_1   .equ CTC_BASE+001h
+CTC_CHANNEL_2   .equ CTC_BASE+002h
+CTC_CHANNEL_3   .equ CTC_BASE+003h
+
+RAM_TOP         .equ 0xbfff
+; workspace variables here vv
+; ------------------------ ^^
+SAVED_SP        .equ RAM_TOP-0x02 ; word
+STACK_TOP       .equ RAM_TOP-0x100
+
+; -------------------------------------------------------
+; Entry
+; -------------------------------------------------------
+.org SN76489_ROM_START
+    push        bc
+    push        de
+    push        hl
+
+    ld          hl, 0
+    add         hl, sp              ; get sp
+    ld          (SAVED_SP), hl      ; save sp for later
+    ld          hl, STACK_TOP
+    ld          sp, hl              ; use own stack
+
+    ld          hl,str_header
+    call        BIOS_PUTS
+
+    ld          hl,SHARED_MEM_START+042h
+    ld          bc, ctc_interrupt   ; install own ctc isr
+    ld          (hl), bc
+
+    di
+
+    call        PSGInit             ; Initialize psglib
+    ld          a,10100111b         ; interrupts enabled
+                                    ; timer mode
+                                    ; prescaler 256
+                                    ; automatic trigger
+                                    ; time constant follows
+                                    ; reset
+                                    ; control word
+    out         (CTC_CHANNEL_1), a
+    ld          a,78                ; 50Hz
+    out         (CTC_CHANNEL_1), a
+
+    ; music must be loaded from 8000
+    ld          hl, 0x8000
+    call        PSGPlayNoRepeat
+
+    ei
+
+exit:
+    ld          hl, (SAVED_SP)
+    ld          sp, hl              ; restore original stack
+
+    pop         hl
+    pop         de
+    pop         bc
+    ret
+
+; -------------------------------------------------------
+; CTC CHAN 1 interrupt handler
+; -------------------------------------------------------
+ctc_interrupt:
+    push        af
+    push        bc
+    push        de
+    push        hl
+
+    call        PSGFrame
+
+    pop         hl
+    pop         de
+    pop         bc
+    pop         af
+    reti
+
+; -------------------------------------------------------
+; Strings
+; -------------------------------------------------------
+str_header:     .db "SN76489 test",00dh,00ah,000h
+
+#include "psglib_zasm.asm"
\ No newline at end of file
diff --git a/apps/sn76489/psglib.asm b/apps/sn76489/psglib.asm
new file mode 100644
index 0000000..1284093
--- /dev/null
+++ b/apps/sn76489/psglib.asm
@@ -0,0 +1,1146 @@
+;================================================================
+; PSGlib - Programmable Sound Generator audio library - by sverx
+;          https://github.com/sverx/PSGlib
+;================================================================
+
+; NOTE: this uses a WLA-DX 'ramsection' at slot 3
+;       If you want to change or remove that,
+;       see the note at the end of this file
+
+.define      PSG_STOPPED         0
+.define      PSG_PLAYING         1
+
+.define      PSGDataPort         $19
+
+.define      PSGLatch            $80
+.define      PSGData             $40
+
+.define      PSGChannel0         %00000000
+.define      PSGChannel1         %00100000
+.define      PSGChannel2         %01000000
+.define      PSGChannel3         %01100000
+.define      PSGVolumeData       %00010000
+
+.define      PSGWait             $38
+.define      PSGSubString        $08
+.define      PSGLoop             $01
+.define      PSGEnd              $00
+
+.define      SFX_CHANNEL2        $01
+.define      SFX_CHANNEL3        $02
+.define      SFX_CHANNELS2AND3   SFX_CHANNEL2|SFX_CHANNEL3
+.define      SFX_CHANNEL0        $04
+.define      SFX_CHANNEL1        $08
+
+.section "PSGInit" free
+; ************************************************************************************
+; initializes the PSG 'engine'
+; destroys AF
+PSGInit:
+  xor a                           ; ld a,PSG_STOPPED
+  ld (PSGMusicStatus),a           ; set music status to PSG_STOPPED
+  ld (PSGSFXStatus),a             ; set SFX status to PSG_STOPPED
+  ld (PSGChannel0SFX),a           ; set channel 0 SFX to PSG_STOPPED
+  ld (PSGChannel1SFX),a           ; set channel 1 SFX to PSG_STOPPED
+  ld (PSGChannel2SFX),a           ; set channel 2 SFX to PSG_STOPPED
+  ld (PSGChannel3SFX),a           ; set channel 3 SFX to PSG_STOPPED
+  ld (PSGMusicVolumeAttenuation),a  ; volume attenuation = none
+  ret
+.ends
+
+.section "PSGPlay and PSGPlayNoRepeat and PSGPlayLoops" free
+; ************************************************************************************
+; all receive in HL the address of the PSG to start playing
+; PSGPlayLoops also receives in A the number of times to loop the PSG
+; destroys AF
+PSGPlayNoRepeat:                  ; we don't want the song ever to loop
+  xor a
+PSGPlayLoops:                     ; we want the song to loop a certain amount of times
+  ld (PSGLoopCounter),a
+  xor a                           ; we don't want the song to loop forever
+  jp +
+PSGPlay:
+  ld a,$1                         ; we want the song to loop forever
++:ld (PSGLoopFlag),a
+  call PSGStop                    ; if there's a tune already playing, we should stop it!
+  ld (PSGMusicStart),hl           ; store the begin point of music
+  ld (PSGMusicPointer),hl         ; set music pointer to begin of music
+  ld (PSGMusicLoopPoint),hl       ; looppointer points to begin too
+  xor a
+  ld (PSGMusicSkipFrames),a       ; reset the skip frames
+  ld (PSGMusicSubstringLen),a     ; reset the substring len (for compression)
+  ld a,PSGLatch|PSGChannel0|PSGVolumeData|$0F   ; latch channel 0, volume=0xF (silent)
+  ld (PSGMusicLastLatch),a        ; reset last latch to chn 0 volume 0
+  ld a,$0F                        ; ensure unused channels remain silent
+  ld (PSGChan0Volume),a
+  ld (PSGChan1Volume),a
+  ld (PSGChan2Volume),a
+  ld (PSGChan3Volume),a
+  ld a,PSG_PLAYING
+  ld (PSGMusicStatus),a           ; set status to PSG_PLAYING
+  ret
+.ends
+
+.section "PSGStop" free
+; ************************************************************************************
+; stops the music (leaving the SFX on, if it's playing)
+; destroys AF
+PSGStop:
+  ld a,(PSGMusicStatus)                         ; if it's already stopped, leave
+  or a
+  ret z
+  ld a,(PSGChannel0SFX)
+  or a
+  jr nz,+
+  ld a,PSGLatch|PSGChannel0|PSGVolumeData|$0F   ; latch channel 0, volume=0xF (silent)
+  out (PSGDataPort),a
++:ld a,(PSGChannel1SFX)
+  or a
+  jr nz,+
+  ld a,PSGLatch|PSGChannel1|PSGVolumeData|$0F   ; latch channel 1, volume=0xF (silent)
+  out (PSGDataPort),a
++:ld a,(PSGChannel2SFX)
+  or a
+  jr nz,+
+  ld a,PSGLatch|PSGChannel2|PSGVolumeData|$0F   ; latch channel 2, volume=0xF (silent)
+  out (PSGDataPort),a
++:ld a,(PSGChannel3SFX)
+  or a
+  jr nz,+
+  ld a,PSGLatch|PSGChannel3|PSGVolumeData|$0F   ; latch channel 3, volume=0xF (silent)
+  out (PSGDataPort),a
++:xor a                                         ; ld a,PSG_STOPPED
+  ld (PSGMusicStatus),a                         ; set status to PSG_STOPPED
+  ret
+.ends
+
+.section "PSGResume" free
+; ************************************************************************************
+; resume a previously stopped music (with volume attenuation if needed)
+; destroys AF,HL
+PSGResume:
+  ld a,(PSGMusicStatus)                         ; if it's already playing, leave
+  or a
+  ret nz
+
+  ld hl,PSGMusicVolumeAttenuation
+  ld l,(hl)                                     ; load volume attenuation in L
+
+  ld a,(PSGChannel0SFX)
+  or a
+  jr nz,_ch1
+  ld a,(PSGChan0LowTone)                        ; restore channel 0 frequency
+  or PSGLatch|PSGChannel0
+  out (PSGDataPort),a
+  ld a,(PSGChan0HighTone)
+  out (PSGDataPort),a
+  ld a,(PSGChan0Volume)                         ; restore channel 0 volume
+  and $0F
+  add a,l
+  cp $0F                                        ; check overflow
+  jr c,+                                        ; if it's <=15 then ok
+  ld a,$0F                                      ; else, reset to 15
++:or PSGLatch|PSGChannel0|PSGVolumeData
+  out (PSGDataPort),a                           ; output the byte
+
+_ch1:
+  ld a,(PSGChannel1SFX)
+  or a
+  jr nz,_ch2
+  ld a,(PSGChan1LowTone)                        ; restore channel 1 frequency
+  or PSGLatch|PSGChannel1
+  out (PSGDataPort),a
+  ld a,(PSGChan1HighTone)
+  out (PSGDataPort),a
+  ld a,(PSGChan1Volume)                         ; restore channel 1 volume
+  and $0F
+  add a,l
+  cp $0F                                        ; check overflow
+  jr c,+                                        ; if it's <=15 then ok
+  ld a,$0F                                      ; else, reset to 15
++:or PSGLatch|PSGChannel1|PSGVolumeData
+  out (PSGDataPort),a
+
+_ch2:
+  ld a,(PSGChannel2SFX)
+  or a
+  jr nz,_ch3
+  ld a,(PSGChan2LowTone)                        ; restore channel 2 frequency
+  or PSGLatch|PSGChannel2
+  out (PSGDataPort),a
+  ld a,(PSGChan2HighTone)
+  out (PSGDataPort),a
+  ld a,(PSGChan2Volume)                         ; restore channel 2 volume
+  and $0F
+  add a,l
+  cp $0F                                        ; check overflow
+  jr c,+                                        ; if it's <=15 then ok
+  ld a,$0F                                      ; else, reset to 15
++:or PSGLatch|PSGChannel2|PSGVolumeData
+  out (PSGDataPort),a
+
+_ch3:
+  ld a,(PSGChannel3SFX)
+  or a
+  jr nz,_leave
+  ld a,(PSGChan3LowTone)                        ; restore channel 3 frequency
+  or PSGLatch|PSGChannel3
+  out (PSGDataPort),a
+  ld a,(PSGChan3Volume)                         ; restore channel 3 volume
+  and $0F
+  add a,l
+  cp $0F                                        ; check overflow
+  jr c,+                                        ; if it's <=15 then ok
+  ld a,$0F                                      ; else, reset to 15
++:or PSGLatch|PSGChannel3|PSGVolumeData
+  out (PSGDataPort),a
+
+_leave:
+  ld a,PSG_PLAYING
+  ld (PSGMusicStatus),a                         ; set status to PSG_PLAYING
+  ret
+.ends
+
+.section "PSGCancelLoop" free
+; ************************************************************************************
+; sets the currently looping music to no more loops after the current
+; destroys AF
+PSGCancelLoop:
+  xor a
+  ld (PSGLoopFlag),a
+  ld (PSGLoopCounter),a
+  ret
+.ends
+
+.section "PSGGetStatus" free
+; ************************************************************************************
+; gets the current status of music into register A
+PSGGetStatus:
+  ld a,(PSGMusicStatus)
+  ret
+.ends
+
+.section "PSGSetMusicVolumeAttenuation" free
+; ************************************************************************************
+; receives in L the volume attenuation for the music (0-15)
+; destroys AF
+PSGSetMusicVolumeAttenuation:
+  ld a,l
+  ld (PSGMusicVolumeAttenuation),a
+  ld a,(PSGMusicStatus)            ; if tune is not playing, leave
+  or a
+  ret z
+
+  ld a,(PSGChannel0SFX)            ; channel 0 busy with SFX?
+  or a
+  jr nz,_restore_channel1          ; if so, skip channel 0
+
+  ld a,(PSGChan0Volume)
+  and $0F
+  add a,l
+  cp $0F                           ; check overflow
+  jr c,+                           ; if it's <=15 then ok
+  ld a,$0F                         ; else, reset to 15
++:or PSGLatch|PSGChannel0|PSGVolumeData
+  out (PSGDataPort),a              ; output the byte
+
+_restore_channel1:
+  ld a,(PSGChannel1SFX)            ; channel 1 busy with SFX?
+  or a
+  jr nz,_restore_channel2          ; if so, skip channel 1
+
+  ld a,(PSGChan1Volume)
+  and $0F
+  add a,l
+  cp $0F                           ; check overflow
+  jr c,+                           ; if it's <=15 then ok
+  ld a,$0F                         ; else, reset to 15
++:or PSGLatch|PSGChannel1|PSGVolumeData
+  out (PSGDataPort),a              ; output the byte
+
+_restore_channel2:
+  ld a,(PSGChannel2SFX)            ; channel 2 busy with SFX?
+  or a
+  jr nz,_restore_channel3          ; if so, skip channel 2
+
+  ld a,(PSGChan2Volume)
+  and $0F
+  add a,l
+  cp $0F                           ; check overflow
+  jr c,+                           ; if it's <=15 then ok
+  ld a,$0F                         ; else, reset to 15
++:or PSGLatch|PSGChannel2|PSGVolumeData
+  out (PSGDataPort),a              ; output the byte
+
+_restore_channel3:
+  ld a,(PSGChannel3SFX)            ; channel 3 busy with SFX?
+  or a
+  ret nz                           ; if so, we're done
+
+  ld a,(PSGChan3Volume)
+  and $0F
+  add a,l
+  cp $0F                           ; check overflow
+  jr c,+                           ; if it's <=15 then ok
+  ld a,$0F                         ; else, reset to 15
++:or PSGLatch|PSGChannel3|PSGVolumeData
+  out (PSGDataPort),a              ; output the byte
+  ret
+.ends
+
+.section "PSGSetSFXVolumeAttenuation" free
+; ************************************************************************************
+; receives in L the volume attenuation for the SFXs (0-15)
+; destroys AF
+PSGSetSFXVolumeAttenuation:
+  ld a,l
+  ld (PSGSFXVolumeAttenuation),a
+  ld a,(PSGSFXStatus)              ; if an SFX is not playing, leave
+  or a
+  ret z
+
+  ld a,(PSGChannel0SFX)            ; channel 0 used by SFX?
+  or a
+  jr z,_restore_channel1           ; if not, skip channel 0
+
+  ld a,(PSGSFXChan0Volume)
+  and $0F
+  add a,l
+  cp $0F                           ; check overflow
+  jr c,+                           ; if it's <=15 then ok
+  ld a,$0F                         ; else, reset to 15
++:or PSGLatch|PSGChannel0|PSGVolumeData
+  out (PSGDataPort),a              ; output the byte
+
+_restore_channel1:
+  ld a,(PSGChannel1SFX)            ; channel 1 used by SFX?
+  or a
+  jr z,_restore_channel2           ; if not, skip channel 1
+
+  ld a,(PSGSFXChan1Volume)
+  and $0F
+  add a,l
+  cp $0F                           ; check overflow
+  jr c,+                           ; if it's <=15 then ok
+  ld a,$0F                         ; else, reset to 15
++:or PSGLatch|PSGChannel1|PSGVolumeData
+  out (PSGDataPort),a              ; output the byte
+
+_restore_channel2:
+  ld a,(PSGChannel2SFX)            ; channel 2 used by SFX?
+  or a
+  jr z,_restore_channel3           ; if not, skip channel 2
+
+  ld a,(PSGSFXChan2Volume)
+  and $0F
+  add a,l
+  cp $0F                           ; check overflow
+  jr c,+                           ; if it's <=15 then ok
+  ld a,$0F                         ; else, reset to 15
++:or PSGLatch|PSGChannel2|PSGVolumeData
+  out (PSGDataPort),a              ; output the byte
+
+_restore_channel3:
+  ld a,(PSGChannel3SFX)            ; channel 3 used by SFX?
+  or a
+  ret z                            ; if not, we're done
+
+  ld a,(PSGSFXChan3Volume)
+  and $0F
+  add a,l
+  cp $0F                           ; check overflow
+  jr c,+                           ; if it's <=15 then ok
+  ld a,$0F                         ; else, reset to 15
++:or PSGLatch|PSGChannel3|PSGVolumeData
+  out (PSGDataPort),a              ; output the byte
+  ret
+.ends
+
+.section "PSGSilenceChannels" free
+; ************************************************************************************
+; sets all PSG channels to volume ZERO
+; destroys AF
+PSGSilenceChannels:
+  ld a,PSGLatch|PSGChannel0|PSGVolumeData|$0F   ; latch channel 0, volume=0xF (silent)
+  out (PSGDataPort),a
+  ld a,PSGLatch|PSGChannel1|PSGVolumeData|$0F   ; latch channel 1, volume=0xF (silent)
+  out (PSGDataPort),a
+  ld a,PSGLatch|PSGChannel2|PSGVolumeData|$0F   ; latch channel 2, volume=0xF (silent)
+  out (PSGDataPort),a
+  ld a,PSGLatch|PSGChannel3|PSGVolumeData|$0F   ; latch channel 3, volume=0xF (silent)
+  out (PSGDataPort),a
+  ret
+.ends
+
+.section "PSGRestoreVolumes" free
+; ************************************************************************************
+; resets all PSG channels to previous volume
+; destroys AF,HL
+PSGRestoreVolumes:
+  ld a,(PSGChannel0SFX)            ; channel 0 busy with SFX?
+  jr nz,_restoreSFX0
+
+  ld a,(PSGMusicStatus)            ; check if tune is playing
+  or a
+  jr z,_chkchn1                    ; if not, skip channel 0
+
+  ld a,(PSGChan0Volume)
+  and $0F
+  ld hl,PSGMusicVolumeAttenuation
+  add a,(hl)
+  cp $0F                           ; check overflow
+  jr c,_write0                     ; if it's <=15 then ok
+  ld a,$0F                         ; else, reset to 15
+  jp _write0
+
+_restoreSFX0:
+  ld a,(PSGSFXChan0Volume)
+  and $0F
+  ld hl,PSGSFXVolumeAttenuation
+  add a,(hl)
+  cp $0F                           ; check overflow
+  jr c,_write0                     ; if it's <=15 then ok
+  ld a,$0F                         ; else, reset to 15
+
+_write0:
+  or PSGLatch|PSGChannel0|PSGVolumeData
+  out (PSGDataPort),a              ; output the byte
+
+_chkchn1:
+  ld a,(PSGChannel1SFX)            ; channel 1 busy with SFX?
+  jr nz,_restoreSFX1
+
+  ld a,(PSGMusicStatus)            ; check if tune is playing
+  or a
+  jr z,_chkchn2                    ; if not, skip channel 1
+
+  ld a,(PSGChan1Volume)
+  and $0F
+  ld hl,PSGMusicVolumeAttenuation
+  add a,(hl)
+  cp $0F                           ; check overflow
+  jr c,_write1                     ; if it's <=15 then ok
+  ld a,$0F                         ; else, reset to 15
+  jp _write1
+
+_restoreSFX1:
+  ld a,(PSGSFXChan1Volume)
+  and $0F
+  ld hl,PSGSFXVolumeAttenuation
+  add a,(hl)
+  cp $0F                           ; check overflow
+  jr c,_write1                     ; if it's <=15 then ok
+  ld a,$0F                         ; else, reset to 15
+
+_write1:
+  or PSGLatch|PSGChannel1|PSGVolumeData
+  out (PSGDataPort),a              ; output the byte
+
+_chkchn2:
+  ld a,(PSGChannel2SFX)            ; channel 2 busy with SFX?
+  jr nz,_restoreSFX2
+
+  ld a,(PSGMusicStatus)            ; check if tune is playing
+  or a
+  jr z,_chkchn3                    ; if not, skip chn2
+
+  ld a,(PSGChan2Volume)
+  and $0F
+  ld hl,PSGMusicVolumeAttenuation
+  add a,(hl)
+  cp $0F                           ; check overflow
+  jr c,_write2                     ; if it's <=15 then ok
+  ld a,$0F                         ; else, reset to 15
+  jp _write2
+
+_restoreSFX2:
+  ld a,(PSGSFXChan2Volume)
+  and $0F
+  ld hl,PSGSFXVolumeAttenuation
+  add a,(hl)
+  cp $0F                           ; check overflow
+  jr c,_write2                     ; if it's <=15 then ok
+  ld a,$0F                         ; else, reset to 15
+
+_write2:
+  or PSGLatch|PSGChannel2|PSGVolumeData
+  out (PSGDataPort),a              ; output the byte
+
+_chkchn3:
+  ld a,(PSGChannel3SFX)            ; channel 3 busy with SFX?
+  jr nz,_restoreSFX3
+
+  ld a,(PSGMusicStatus)            ; check if tune is playing
+  or a
+  ret z                            ; if not, we've done
+
+  ld a,(PSGChan3Volume)
+  and $0F
+  ld hl,PSGMusicVolumeAttenuation
+  add a,(hl)
+  cp $0F                           ; check overflow
+  jr c,_write3                     ; if it's <=15 then ok
+  ld a,$0F                         ; else, reset to 15
+  jp _write3
+
+_restoreSFX3:
+  ld a,(PSGSFXChan3Volume)
+  and $0F
+  ld hl,PSGSFXVolumeAttenuation
+  add a,(hl)
+  cp $0F                           ; check overflow
+  jr c,_write3                     ; if it's <=15 then ok
+  ld a,$0F                         ; else, reset to 15
+
+_write3:
+  or PSGLatch|PSGChannel3|PSGVolumeData
+  out (PSGDataPort),a              ; output the byte
+  ret
+.ends
+
+.section "PSGSFXPlay and PSGSFXPlayLoop" free
+; ************************************************************************************
+; receives in HL the address of the SFX PSG to start
+; receives in C the mask that indicates which channel(s) the SFX will use
+; destroys AF
+PSGSFXPlayLoop:
+  ld a,1                        ; SFX _IS_ a looping one
+  jp +
+PSGSFXPlay:
+  xor a                         ; SFX is _NOT_ a looping one
++:ld (PSGSFXLoopFlag),a
+  call PSGSFXStop               ; if there's a SFX already playing, we should stop it!
+  ld (PSGSFXStart),hl           ; store begin of SFX
+  ld (PSGSFXPointer),hl         ; set the pointer to begin of SFX
+  ld (PSGSFXLoopPoint),hl       ; looppointer points to begin too
+  xor a
+  ld (PSGSFXSkipFrames),a       ; reset the skip frames
+  ld (PSGSFXSubstringLen),a     ; reset the substring len
+  bit 2,c                       ; channel 0 needed?
+  jr z,+
+  ld a,PSG_PLAYING
+  ld (PSGChannel0SFX),a
++:bit 3,c                       ; channel 1 needed?
+  jr z,+
+  ld a,PSG_PLAYING
+  ld (PSGChannel1SFX),a
++:bit 0,c                       ; channel 2 needed?
+  jr z,+
+  ld a,PSG_PLAYING
+  ld (PSGChannel2SFX),a
++:bit 1,c                       ; channel 3 needed?
+  jr z,+
+  ld a,PSG_PLAYING
+  ld (PSGChannel3SFX),a
++:ld (PSGSFXStatus),a           ; set SFXstatus to PSG_PLAYING if SFX uses at least one channel (0=PSG_STOPPED otherwise)
+  ld a,(PSGMusicStatus)         ; check if a tune is currently playing
+  or a
+  ret z                         ; if not, we've done
+
+  ld a,(PSGChan3LowTone)        ; test if music playing on channel 3 uses the frequency of channel 2
+  and 3
+  cp 3
+  ret nz                        ; if channel 3 doesn't use the frequency of channel 2 we're done
+
+  ld a,PSG_PLAYING
+  ld (PSGChannel3SFX),a         ; otherwise mark channel 3 as occupied by the SFX
+  ld a,PSGLatch|PSGChannel3|PSGVolumeData|$0F   ; and silence channel 3
+  out (PSGDataPort),a
+  ret
+.ends
+
+.section "PSGSFXStop" free
+; ************************************************************************************
+; stops the SFX (leaving the music on, if it's playing)
+; destroys AF
+PSGSFXStop:
+  ld a,(PSGSFXStatus)            ; check status
+  or a
+  ret z                          ; no SFX playing, leave
+
+  ld a,(PSGChannel0SFX)          ; channel 0 playing?
+  or a
+  jr z,+
+  ld a,PSGLatch|PSGChannel0|PSGVolumeData|$0F    ; latch channel 0, volume=0xF (silent)
+  out (PSGDataPort),a
++:ld a,(PSGChannel1SFX)          ; channel 1 playing?
+  or a
+  jr z,+
+  ld a,PSGLatch|PSGChannel1|PSGVolumeData|$0F    ; latch channel 1, volume=0xF (silent)
+  out (PSGDataPort),a
++:ld a,(PSGChannel2SFX)          ; channel 2 playing?
+  or a
+  jr z,+
+  ld a,PSGLatch|PSGChannel2|PSGVolumeData|$0F    ; latch channel 2, volume=0xF (silent)
+  out (PSGDataPort),a
++:ld a,(PSGChannel3SFX)          ; channel 3 playing?
+  or a
+  jr z,+
+  ld a,PSGLatch|PSGChannel3|PSGVolumeData|$0F    ; latch channel 3, volume=0xf (silent)
+  out (PSGDataPort),a
++:ld a,(PSGMusicStatus)          ; check if a tune is playing
+  or a
+  jp z,_skipRestore              ; if it's not playing, skip restoring PSG values
+
+  ld a,(PSGChannel0SFX)          ; channel 0 playing?
+  or a
+  jr z,_skip_chn0
+  ld a,(PSGChan0LowTone)
+  and $0F                        ; use only low 4 bits of byte
+  or PSGLatch|PSGChannel0        ; latch channel 0, low part of tone
+  out (PSGDataPort),a
+  ld a,(PSGChan0HighTone)        ; high part of tone (latched channel 0, tone)
+  and $3F                        ; use only low 6 bits of byte
+  out (PSGDataPort),a
+  ld a,(PSGChan0Volume)          ; restore music' channel 0 volume
+  and $0F                        ; use only low 4 bits of byte
+  push bc
+    ld b,a                            ; save it temporary
+    ld a,(PSGMusicVolumeAttenuation)  ;
+    add a,b
+    cp $0F                            ; check overflow
+    jr c,+                            ; if it's <=15 then ok
+    ld a,$0F                          ; else, reset to 15
++:  or PSGLatch|PSGChannel0|PSGVolumeData
+    out (PSGDataPort),a              ; output the byte
+  pop bc
+
+_skip_chn0:
+  ld a,(PSGChannel1SFX)          ; channel 1 playing?
+  or a
+  jr z,_skip_chn1
+  ld a,(PSGChan1LowTone)
+  and $0F                        ; use only low 4 bits of byte
+  or PSGLatch|PSGChannel1        ; latch channel 1, low part of tone
+  out (PSGDataPort),a
+  ld a,(PSGChan1HighTone)        ; high part of tone (latched channel 1, tone)
+  and $3F                        ; use only low 6 bits of byte
+  out (PSGDataPort),a
+  ld a,(PSGChan1Volume)          ; restore music' channel 1 volume
+  and $0F                        ; use only low 4 bits of byte
+  push bc
+    ld b,a                            ; save it temporary
+    ld a,(PSGMusicVolumeAttenuation)  ;
+    add a,b
+    cp $0F                            ; check overflow
+    jr c,+                            ; if it's <=15 then ok
+    ld a,$0F                          ; else, reset to 15
++:  or PSGLatch|PSGChannel1|PSGVolumeData
+    out (PSGDataPort),a              ; output the byte
+  pop bc
+
+_skip_chn1:
+  ld a,(PSGChannel2SFX)          ; channel 2 playing?
+  or a
+  jr z,_skip_chn2
+  ld a,(PSGChan2LowTone)
+  and $0F                        ; use only low 4 bits of byte
+  or PSGLatch|PSGChannel2        ; latch channel 2, low part of tone
+  out (PSGDataPort),a
+  ld a,(PSGChan2HighTone)        ; high part of tone (latched channel 2, tone)
+  and $3F                        ; use only low 6 bits of byte
+  out (PSGDataPort),a
+  ld a,(PSGChan2Volume)          ; restore music' channel 2 volume
+  and $0F                        ; use only low 4 bits of byte
+  push bc
+    ld b,a                            ; save it temporary
+    ld a,(PSGMusicVolumeAttenuation)  ;
+    add a,b
+    cp $0F                            ; check overflow
+    jr c,+                            ; if it's <=15 then ok
+    ld a,$0F                          ; else, reset to 15
++:  or PSGLatch|PSGChannel2|PSGVolumeData
+    out (PSGDataPort),a              ; output the byte
+  pop bc
+
+_skip_chn2:
+  ld a,(PSGChannel3SFX)          ; channel 3 playing?
+  or a
+  jr z,_skip_chn3
+  ld a,(PSGChan3LowTone)
+  and $07                        ; use only low 3 bits of byte
+  or PSGLatch|PSGChannel3        ; latch channel 3, low part of tone (no high part)
+  out (PSGDataPort),a
+  ld a,(PSGChan3Volume)          ; restore music' channel 3 volume
+  and $0F                        ; use only low 4 bits of byte
+  push bc
+    ld b,a                            ; save it temporary
+    ld a,(PSGMusicVolumeAttenuation)  ;
+    add a,b
+    cp $0F                            ; check overflow
+    jr c,+                            ; if it's <=15 then ok
+    ld a,$0F                          ; else, reset to 15
++:  or PSGLatch|PSGChannel3|PSGVolumeData
+    out (PSGDataPort),a              ; output the byte
+  pop bc
+_skip_chn3:
+  xor a                          ; ld a,PSG_STOPPED
+_skipRestore:
+  ld (PSGChannel0SFX),a
+  ld (PSGChannel1SFX),a
+  ld (PSGChannel2SFX),a
+  ld (PSGChannel3SFX),a
+  ld (PSGSFXStatus),a            ; set status to PSG_STOPPED
+  ret
+.ends
+
+.section "PSGSFXCancelLoop" free
+; ************************************************************************************
+; sets the currently looping SFX to no more loops after the current
+; destroys AF
+PSGSFXCancelLoop:
+  xor a
+  ld (PSGSFXLoopFlag),a
+  ret
+.ends
+
+.section "PSGSFXGetStatus" free
+; ************************************************************************************
+; gets the current SFX status into register A
+PSGSFXGetStatus:
+  ld a,(PSGSFXStatus)
+  ret
+.ends
+
+.section "PSGFrame" free
+; ************************************************************************************
+; processes a music frame
+; destroys AF,HL,BC
+PSGFrame:
+  ld a,(PSGMusicStatus)          ; check if we have got to play a tune
+  or a
+  ret z
+
+  ld a,(PSGMusicSkipFrames)      ; check if we havve got to skip frames
+  or a
+  jp nz,_skipFrame
+
+  ld hl,(PSGMusicPointer)        ; read current address
+
+_intLoop:
+  ld b,(hl)                      ; load PSG byte (in B)
+  inc hl                         ; point to next byte
+  ld a,(PSGMusicSubstringLen)    ; read substring len
+  or a
+  jr z,_continue                 ; check if it is 0 (we are not in a substring)
+  dec a                          ; decrease len
+  ld (PSGMusicSubstringLen),a    ; save len
+  jr nz,_continue
+  ld hl,(PSGMusicSubstringRetAddr)  ; substring is over, retrieve return address
+
+_continue:
+  ld a,b                         ; copy PSG byte into A
+  cp PSGLatch                    ; is it a latch?
+  jr c,_noLatch                  ; if < $80 then it is NOT a latch
+  ld (PSGMusicLastLatch),a       ; it is a latch - save it in "LastLatch"
+
+  ; we have got the latch PSG byte both in A and in B
+  ; and we have to check if the value should pass to PSG or not
+  bit 4,a                        ; test if it is a volume
+  jr nz,_latch_Volume            ; jump if volume data
+  bit 6,a                        ; test if the latch it is for channels 0-1 or for 2-3
+  jp nz,_latch_chn23             ; jump if it is for channels 2-3
+
+  ; we have got the latch (tone, chn 0 or 1) PSG byte both in A and in B
+  ; and we have to check if the value should be passed to PSG or not
+  bit 5,a                        ; test if tone it is for channel 0 or 1
+  jr z,_ifchn0                   ; jump if channel 0
+  ld (PSGChan1LowTone),a         ; save tone LOW data
+  ld a,(PSGChannel1SFX)          ; channel 1 available for music?
+  or a
+  jr z,_send2PSG_B               ; then send data
+  jp _intLoop
+_ifchn0:
+  ld (PSGChan0LowTone),a         ; save tone LOW data
+  ld a,(PSGChannel0SFX)          ; channel 0 available for music?
+  or a
+  jr z,_send2PSG_B               ; then send data
+  jp _intLoop
+
+_latch_chn23:
+  ; we have got the latch (tone, chn 2 or 3) PSG byte both in A and in B
+  ; and we have to check if the value should be passed to PSG or not
+  bit 5,a                        ; test if tone it is for channel 2 or 3
+  jr z,_ifchn2                   ; jump if channel 2
+  ld (PSGChan3LowTone),a         ; save tone LOW data
+  ld a,(PSGChannel3SFX)          ; channel 3 available for music?
+  or a
+  jp nz,_intLoop
+  ld a,(PSGChan3LowTone)
+  and 3                          ; test if channel 3 is set to use the frequency of channel 2
+  cp 3
+  jr nz,_send2PSG_B              ; if channel 3 does not use frequency of channel 2 jump
+  ld a,(PSGChannel2SFX)          ; test if an SFX is playing on channel 2
+  or a
+  jr z,_send2PSG_B               ; if no SFX is playing on channel 2 jump
+  ld (PSGChannel3SFX),a          ; otherwise mark channel 3 as occupied
+  ld a,PSGLatch|PSGChannel3|PSGVolumeData|$0F   ; and silence channel 3
+  out (PSGDataPort),a
+  jp _intLoop
+_ifchn2:
+  ld (PSGChan2LowTone),a         ; save tone LOW data
+  ld a,(PSGChannel2SFX)          ; channel 2 available for music?
+  or a
+  jr z,_send2PSG_B
+  jp _intLoop
+
+_noLatch:
+  cp PSGData
+  jr c,_command                  ; if < $40 then it is a command
+  ; it's a data
+  ld a,(PSGMusicLastLatch)       ; retrieve last latch
+  jp _output_NoLatch
+
+_latch_Volume:
+  bit 6,a                        ; test if the latch it is for channels 0-1 or for 2-3
+  jr nz,_latch_Volume_23         ; volume is for channel 2 or 3
+  bit 5,a                        ; test if volume it is for channel 0 or 1
+  jr z,_ifchn0v                  ; jump for channel 0
+  ld (PSGChan1Volume),a          ; save volume data
+  ld a,(PSGChannel1SFX)          ; channel 1 available for music?
+  or a
+  jr z,_sendVolume2PSG_B
+  jp _intLoop
+_ifchn0v:
+  ld (PSGChan0Volume),a          ; save volume data
+  ld a,(PSGChannel0SFX)          ; channel 0 available for music?
+  or a
+  jr z,_sendVolume2PSG_B
+  jp _intLoop
+
+_send2PSG_B:
+  ld a,b
+_send2PSG_A:
+  out (PSGDataPort),a            ; output the byte
+  jp _intLoop
+
+_latch_Volume_23:
+  bit 5,a                        ; test if volume it is for channel 2 or 3
+  jr z,_chn2                     ; jump for channel 2
+  ld (PSGChan3Volume),a          ; save volume data
+  ld a,(PSGChannel3SFX)          ; channel 3 available for music?
+  or a
+  jr z,_sendVolume2PSG_B
+  jp _intLoop
+_chn2:
+  ld (PSGChan2Volume),a          ; save volume data
+  ld a,(PSGChannel2SFX)          ; channel 2 available for music?
+  or a
+  jr z,_sendVolume2PSG_B
+  jp _intLoop
+
+_skipFrame:
+  dec a
+  ld (PSGMusicSkipFrames),a
+  ret
+
+_command:
+  cp PSGWait
+  jr z,_done                     ; no additional frames
+  jr c,_otherCommands            ; other commands?
+  and $07                        ; take only the last 3 bits for skip frames
+  ld (PSGMusicSkipFrames),a      ; we got additional frames
+_done:
+  ld (PSGMusicPointer),hl        ; save current address
+  ret                            ; frame done
+
+_otherCommands:
+  cp PSGSubString
+  jr nc,_substring
+  cp PSGEnd
+  jr z,_musicLoop
+  cp PSGLoop
+  jr z,_setLoopPoint
+
+  ; ***************************************************************************
+  ; we should never get here!
+  ; if we do, it means the PSG file is probably corrupted, so we just RET
+  ; ***************************************************************************
+
+  ret
+
+_sendVolume2PSG_B:
+  ld a,b
+_sendVolume2PSG_A:
+  ld c,a                           ; save the PSG command byte
+  and $0F                          ; keep lower nibble
+  ld b,a                           ; save value
+  ld a,(PSGMusicVolumeAttenuation) ; load volume attenuation
+  add a,b                          ; add value
+  cp $0F                           ; check overflow
+  jr c,_no_overflow                ; if it is <=15 then ok
+  ld a,$0F                         ; else, reset to 15
+_no_overflow:
+  ld b,a                           ; save new attenuated volume value
+  ld a,c                           ; retrieve PSG command
+  and $F0                          ; keep upper nibble
+  or b                             ; set attenuated volume
+  out (PSGDataPort),a              ; output the byte
+  jp _intLoop
+
+_output_NoLatch:
+  ; we got the last latch in A and the PSG data in B
+  ; and we have to check if the value should pass to PSG or not
+  ; note that non-latch commands can be only contain frequencies (no volumes)
+  ; for channels 0,1,2 only (no noise)
+  bit 6,a                        ; test if the latch it is for channels 0-1 or for chn 2
+  jr nz,_high_part_Tone_ch2      ; it is tone data for channel 2
+
+  bit 5,a                        ; test if latch is for channel 0 or 1
+  jr nz,_high_part_Tone_ch1      ; it is tone data for channel 1
+
+  ; we got the last latch in A and the PSG data in B
+  ; and we have to check if the value should pass to PSG or not
+  ld a,b                         ; move PSG data in A
+  ld (PSGChan0HighTone),a        ; save channel 0 tone HIGH data
+  ld a,(PSGChannel0SFX)          ; channel 0 available for music?
+  or a
+  jr z,_send2PSG_B
+  jp _intLoop
+
+_high_part_Tone_ch1:
+  ; we got the last latch in A and the PSG data in B
+  ; and we have to check if the value should pass to PSG or not
+  ld a,b                         ; move PSG data in A
+  ld (PSGChan1HighTone),a        ; save channel 1 tone HIGH data
+  ld a,(PSGChannel1SFX)          ; channel 1 available for music?
+  or a
+  jr z,_send2PSG_B
+  jp _intLoop
+
+_high_part_Tone_ch2:
+  ; we got the last latch in A and the PSG data in B
+  ; and we have to check if the value should pass to PSG or not
+  ; PSG data can only be for channel 2, here
+  ld a,b                         ; move PSG data in A
+  ld (PSGChan2HighTone),a        ; save channel 2 tone HIGH data
+  ld a,(PSGChannel2SFX)          ; channel 2 available for music
+  or a
+  jp z,_send2PSG_B               ; TOO FAR for JR here :|
+  jp _intLoop
+
+_setLoopPoint:
+  ld (PSGMusicLoopPoint),hl
+  jp _intLoop
+
+_musicLoop:
+  ld hl,(PSGMusicLoopPoint)
+  ld a,(PSGLoopFlag)               ; infinite loop requested?
+  or a
+  jp nz,_intLoop                   ; Yes: do loop
+  ld a,(PSGLoopCounter)            ; one more loop requested?
+  or a
+  jp z,PSGStop                     ; No: stop the music! (tail call optimization)
+  dec a
+  ld (PSGLoopCounter),a            ; decrement loop counter
+  jp _intLoop                      ; do loop
+
+_substring:
+  sub PSGSubString-4                  ; len is value - $08 + 4
+  ld (PSGMusicSubstringLen),a         ; save len
+  ld c,(hl)                           ; load substring address (offset)
+  inc hl
+  ld b,(hl)
+  inc hl
+  ld (PSGMusicSubstringRetAddr),hl    ; save return address
+  ld hl,(PSGMusicStart)
+  add hl,bc                           ; make substring current
+  jp _intLoop
+.ends
+
+.section "PSGSFXFrame" free
+; ************************************************************************************
+; processes a SFX frame
+; destroys AF,HL,BC
+PSGSFXFrame:
+  ld a,(PSGSFXStatus)            ; check if we have got to play SFX
+  or a
+  ret z
+
+  ld a,(PSGSFXSkipFrames)        ; check if we have got to skip frames
+  or a
+  jp nz,_skipSFXFrame
+
+  ld hl,(PSGSFXPointer)          ; read current SFX address
+
+_intSFXLoop:
+  ld b,(hl)                      ; load a byte in B, temporary
+  inc hl                         ; point to next byte
+  ld a,(PSGSFXSubstringLen)      ; read substring len
+  or a                           ; check if it is 0 (we are not in a substring)
+  jr z,_SFXcontinue
+  dec a                          ; decrease len
+  ld (PSGSFXSubstringLen),a      ; save len
+  jr nz,_SFXcontinue
+  ld hl,(PSGSFXSubstringRetAddr) ; substring over, retrieve return address
+
+_SFXcontinue:
+  ld a,b                         ; restore byte
+  cp PSGData
+  jp c,_SFXcommand               ; if less than $40 then it is a command
+  bit 7,a                        ; check if it is a latch
+  jr z,_SFXoutbyte               ; if not, output it directly
+  bit 4,a                        ; check if it is a volume byte
+  jr z,_SFXoutbyte               ; if not, output it directly
+
+  bit 6,a                        ; check if it is volume for channels 0-1 or for 2-3
+  jr nz,_SFXchn23
+
+  bit 5,a                        ; check if it is volume for channel 0 or channel 1
+  jr nz,_SFXvolumechn1
+  ld (PSGSFXChan0Volume),a
+  jr _SFXoutvolume
+
+_SFXvolumechn1:
+  ld (PSGSFXChan1Volume),a
+  jr _SFXoutvolume
+
+_SFXchn23:
+  bit 5,a                        ; check if it is volume for channel 2 or channel 3
+  jr nz,_SFXvolumechn3
+  ld (PSGSFXChan2Volume),a
+  jr _SFXoutvolume
+
+_SFXvolumechn3:
+  ld (PSGSFXChan3Volume),a
+
+_SFXoutvolume:
+  and $0F                        ; keep lower nibble
+  ld c,a                         ; save value
+  ld a,(PSGSFXVolumeAttenuation) ; load volume attenuation
+  add a,c                        ; add value
+  cp $0F                         ; check overflow
+  jr c,_no_overflow_SFX          ; if it is <=15 then ok
+  ld a,$0F                       ; else, reset to 15
+_no_overflow_SFX:
+  ld c,a                         ; save new attenuated volume value
+  ld a,b                         ; retrieve original PSG command
+  and $F0                        ; keep upper nibble (channel+volume bits)
+  or c                           ; set attenuated SFX volume
+_SFXoutbyte:
+  out (PSGDataPort),a            ; output the byte
+  jp _intSFXLoop
+
+_skipSFXFrame:
+  dec a
+  ld (PSGSFXSkipFrames),a
+  ret
+
+_SFXcommand:
+  cp PSGWait
+  jr z,_SFXdone                  ; no additional frames
+  jr c,_SFXotherCommands         ; other commands?
+  and $07                        ; take only the last 3 bits for skip frames
+  ld (PSGSFXSkipFrames),a        ; we got additional frames to skip
+_SFXdone:
+  ld (PSGSFXPointer),hl          ; save current address
+  ret                            ; frame done
+
+_SFXotherCommands:
+  cp PSGSubString
+  jr nc,_SFXsubstring
+  cp PSGEnd
+  jr z,_sfxLoop
+  cp PSGLoop
+  jr z,_SFXsetLoopPoint
+
+  ; ***************************************************************************
+  ; we should never get here!
+  ; if we do, it means the PSG SFX file is probably corrupted, so we just RET
+  ; ***************************************************************************
+
+  ret
+
+_SFXsetLoopPoint:
+  ld (PSGSFXLoopPoint),hl
+  jp _intSFXLoop
+
+_sfxLoop:
+  ld a,(PSGSFXLoopFlag)               ; is it a looping SFX?
+  or a
+  jp z,PSGSFXStop                     ; No:stop it! (tail call optimization)
+  ld hl,(PSGSFXLoopPoint)
+  ld (PSGSFXPointer),hl
+  jp _intSFXLoop
+
+_SFXsubstring:
+  sub PSGSubString-4                  ; len is value - $08 + 4
+  ld (PSGSFXSubstringLen),a           ; save len
+  ld c,(hl)                           ; load substring address (offset)
+  inc hl
+  ld b,(hl)
+  inc hl
+  ld (PSGSFXSubstringRetAddr),hl    ; save return address
+  ld hl,(PSGSFXStart)
+  add hl,bc                         ; make substring current
+  jp _intSFXLoop
+.ends
+
+; NOTE: if you don't want to use a ramsection,
+;       comment the ".ramsection" line and
+;       uncomment the next ".enum" one,
+;       setting .enum start RAM address
+;       according to your needs.
+;       Also change ".ends" into ".ende" at end of this file
+
+;.ramsection "PSGlib variables" slot 3
+.enum $c000 export                ; PSGlib variables location in RAM
+  ; fundamental vars
+  PSGMusicStatus             db    ; are we playing a background music?
+  PSGMusicStart              dw    ; the pointer to the beginning of music
+  PSGMusicPointer            dw    ; the pointer to the current
+  PSGMusicLoopPoint          dw    ; the pointer to the loop begin
+  PSGMusicSkipFrames         db    ; the frames we need to skip
+  PSGLoopFlag                db    ; the tune should loop forever or not (flag)
+  PSGLoopCounter             db    ; how many times the tune should loop
+  PSGMusicLastLatch          db    ; the last PSG music latch
+
+  ; decompression vars
+  PSGMusicSubstringLen       db    ; lenght of the substring we are playing
+  PSGMusicSubstringRetAddr   dw    ; return to this address when substring is over
+
+  ; command buffers
+  PSGChan0Volume             db       ; the volume for channel 0
+  PSGChan1Volume             db       ; the volume for channel 1
+  PSGChan2Volume             db       ; the volume for channel 2
+  PSGChan3Volume             db       ; the volume for channel 3
+
+  PSGChan0LowTone            db       ; the low tone bits for channels 0
+  PSGChan1LowTone            db       ; the low tone bits for channels 1
+  PSGChan2LowTone            db       ; the low tone bits for channels 2
+  PSGChan3LowTone            db       ; the low tone bits for channels 3
+  PSGChan0HighTone           db       ; the high tone bits for channel 0
+  PSGChan1HighTone           db       ; the high tone bits for channel 1
+  PSGChan2HighTone           db       ; the high tone bits for channel 2
+
+  PSGMusicVolumeAttenuation  db       ; the volume attenuation applied to the tune (0-15)
+
+  ; ******* SFX *************
+
+  ; flags for SFX channels usage
+  PSGChannel0SFX             db       ; !0 means channel 0 is allocated to SFX
+  PSGChannel1SFX             db       ; !0 means channel 1 is allocated to SFX
+  PSGChannel2SFX             db       ; !0 means channel 2 is allocated to SFX
+  PSGChannel3SFX             db       ; !0 means channel 3 is allocated to SFX
+
+  ; command buffers for SFX
+  PSGSFXChan0Volume          db       ; the volume for channel 0
+  PSGSFXChan1Volume          db       ; the volume for channel 1
+  PSGSFXChan2Volume          db       ; the volume for channel 2
+  PSGSFXChan3Volume          db       ; the volume for channel 3
+
+  PSGSFXVolumeAttenuation    db       ; the volume attenuation applied to the SFX (0-15)
+
+  ; fundamental vars for SFX
+  PSGSFXStatus               db       ; are we playing a SFX?
+  PSGSFXStart                dw       ; the pointer to the beginning of SFX
+  PSGSFXPointer              dw       ; the pointer to the current address
+  PSGSFXLoopPoint            dw       ; the pointer to the loop begin
+  PSGSFXSkipFrames           db       ; the frames we need to skip
+  PSGSFXLoopFlag             db       ; the SFX should loop or not (flag)
+
+  ; decompression vars for SFX
+  PSGSFXSubstringLen         db       ; lenght of the substring we are playing
+  PSGSFXSubstringRetAddr     dw       ; return to this address when substring is over
+.ends
+;.ende                    ; in case you want to use .enum instead of .ramsection
\ No newline at end of file
diff --git a/apps/sn76489/psglib_zasm.asm b/apps/sn76489/psglib_zasm.asm
new file mode 100644
index 0000000..2e55640
--- /dev/null
+++ b/apps/sn76489/psglib_zasm.asm
@@ -0,0 +1,1106 @@
+;================================================================
+; PSGlib - Programmable Sound Generator audio library - by sverx
+;          https://github.com/sverx/PSGlib
+;================================================================
+
+; zasm port for z80_monitor. The code is included in the application ROM and
+; its workspace occupies RAM immediately above the application's private stack.
+
+PSG_STOPPED                    .equ 0
+PSG_PLAYING                    .equ 1
+
+PSGDataPort                    .equ 0x19
+
+PSGLatch                       .equ 0x80
+PSGData                        .equ 0x40
+
+PSGChannel0                    .equ 00000000b
+PSGChannel1                    .equ 00100000b
+PSGChannel2                    .equ 01000000b
+PSGChannel3                    .equ 01100000b
+PSGVolumeData                  .equ 00010000b
+
+PSGWait                        .equ 0x38
+PSGSubString                   .equ 0x08
+PSGLoop                        .equ 0x01
+PSGEnd                         .equ 0x00
+
+SFX_CHANNEL2                   .equ 0x01
+SFX_CHANNEL3                   .equ 0x02
+SFX_CHANNELS2AND3              .equ SFX_CHANNEL2|SFX_CHANNEL3
+SFX_CHANNEL0                   .equ 0x04
+SFX_CHANNEL1                   .equ 0x08
+
+; ************************************************************************************
+; initializes the PSG 'engine'
+; destroys AF
+PSGInit:
+  xor a                           ; ld a,PSG_STOPPED
+  ld (PSGMusicStatus),a           ; set music status to PSG_STOPPED
+  ld (PSGSFXStatus),a             ; set SFX status to PSG_STOPPED
+  ld (PSGChannel0SFX),a           ; set channel 0 SFX to PSG_STOPPED
+  ld (PSGChannel1SFX),a           ; set channel 1 SFX to PSG_STOPPED
+  ld (PSGChannel2SFX),a           ; set channel 2 SFX to PSG_STOPPED
+  ld (PSGChannel3SFX),a           ; set channel 3 SFX to PSG_STOPPED
+  ld (PSGMusicVolumeAttenuation),a  ; volume attenuation = none
+  ret
+
+; ************************************************************************************
+; all receive in HL the address of the PSG to start playing
+; PSGPlayLoops also receives in A the number of times to loop the PSG
+; destroys AF
+PSGPlayNoRepeat:                  ; we don't want the song ever to loop
+  xor a
+PSGPlayLoops:                     ; we want the song to loop a certain amount of times
+  ld (PSGLoopCounter),a
+  xor a                           ; we don't want the song to loop forever
+  jp _psglib_anon_01
+PSGPlay:
+  ld a,0x1                         ; we want the song to loop forever
+_psglib_anon_01:ld (PSGLoopFlag),a
+  call PSGStop                    ; if there's a tune already playing, we should stop it!
+  ld (PSGMusicStart),hl           ; store the begin point of music
+  ld (PSGMusicPointer),hl         ; set music pointer to begin of music
+  ld (PSGMusicLoopPoint),hl       ; looppointer points to begin too
+  xor a
+  ld (PSGMusicSkipFrames),a       ; reset the skip frames
+  ld (PSGMusicSubstringLen),a     ; reset the substring len (for compression)
+  ld a,PSGLatch|PSGChannel0|PSGVolumeData|0x0F   ; latch channel 0, volume=0xF (silent)
+  ld (PSGMusicLastLatch),a        ; reset last latch to chn 0 volume 0
+  ld a,0x0F                        ; ensure unused channels remain silent
+  ld (PSGChan0Volume),a
+  ld (PSGChan1Volume),a
+  ld (PSGChan2Volume),a
+  ld (PSGChan3Volume),a
+  ld a,PSG_PLAYING
+  ld (PSGMusicStatus),a           ; set status to PSG_PLAYING
+  ret
+
+; ************************************************************************************
+; stops the music (leaving the SFX on, if it's playing)
+; destroys AF
+PSGStop:
+  ld a,(PSGMusicStatus)                         ; if it's already stopped, leave
+  or a
+  ret z
+  ld a,(PSGChannel0SFX)
+  or a
+  jr nz,_psglib_anon_02
+  ld a,PSGLatch|PSGChannel0|PSGVolumeData|0x0F   ; latch channel 0, volume=0xF (silent)
+  out (PSGDataPort),a
+_psglib_anon_02:ld a,(PSGChannel1SFX)
+  or a
+  jr nz,_psglib_anon_03
+  ld a,PSGLatch|PSGChannel1|PSGVolumeData|0x0F   ; latch channel 1, volume=0xF (silent)
+  out (PSGDataPort),a
+_psglib_anon_03:ld a,(PSGChannel2SFX)
+  or a
+  jr nz,_psglib_anon_04
+  ld a,PSGLatch|PSGChannel2|PSGVolumeData|0x0F   ; latch channel 2, volume=0xF (silent)
+  out (PSGDataPort),a
+_psglib_anon_04:ld a,(PSGChannel3SFX)
+  or a
+  jr nz,_psglib_anon_05
+  ld a,PSGLatch|PSGChannel3|PSGVolumeData|0x0F   ; latch channel 3, volume=0xF (silent)
+  out (PSGDataPort),a
+_psglib_anon_05:xor a                                         ; ld a,PSG_STOPPED
+  ld (PSGMusicStatus),a                         ; set status to PSG_STOPPED
+  ret
+
+; ************************************************************************************
+; resume a previously stopped music (with volume attenuation if needed)
+; destroys AF,HL
+PSGResume:
+  ld a,(PSGMusicStatus)                         ; if it's already playing, leave
+  or a
+  ret nz
+
+  ld hl,PSGMusicVolumeAttenuation
+  ld l,(hl)                                     ; load volume attenuation in L
+
+  ld a,(PSGChannel0SFX)
+  or a
+  jr nz,_ch1
+  ld a,(PSGChan0LowTone)                        ; restore channel 0 frequency
+  or PSGLatch|PSGChannel0
+  out (PSGDataPort),a
+  ld a,(PSGChan0HighTone)
+  out (PSGDataPort),a
+  ld a,(PSGChan0Volume)                         ; restore channel 0 volume
+  and 0x0F
+  add a,l
+  cp 0x0F                                        ; check overflow
+  jr c,_psglib_anon_06                                        ; if it's <=15 then ok
+  ld a,0x0F                                      ; else, reset to 15
+_psglib_anon_06:or PSGLatch|PSGChannel0|PSGVolumeData
+  out (PSGDataPort),a                           ; output the byte
+
+_ch1:
+  ld a,(PSGChannel1SFX)
+  or a
+  jr nz,_ch2
+  ld a,(PSGChan1LowTone)                        ; restore channel 1 frequency
+  or PSGLatch|PSGChannel1
+  out (PSGDataPort),a
+  ld a,(PSGChan1HighTone)
+  out (PSGDataPort),a
+  ld a,(PSGChan1Volume)                         ; restore channel 1 volume
+  and 0x0F
+  add a,l
+  cp 0x0F                                        ; check overflow
+  jr c,_psglib_anon_07                                        ; if it's <=15 then ok
+  ld a,0x0F                                      ; else, reset to 15
+_psglib_anon_07:or PSGLatch|PSGChannel1|PSGVolumeData
+  out (PSGDataPort),a
+
+_ch2:
+  ld a,(PSGChannel2SFX)
+  or a
+  jr nz,_ch3
+  ld a,(PSGChan2LowTone)                        ; restore channel 2 frequency
+  or PSGLatch|PSGChannel2
+  out (PSGDataPort),a
+  ld a,(PSGChan2HighTone)
+  out (PSGDataPort),a
+  ld a,(PSGChan2Volume)                         ; restore channel 2 volume
+  and 0x0F
+  add a,l
+  cp 0x0F                                        ; check overflow
+  jr c,_psglib_anon_08                                        ; if it's <=15 then ok
+  ld a,0x0F                                      ; else, reset to 15
+_psglib_anon_08:or PSGLatch|PSGChannel2|PSGVolumeData
+  out (PSGDataPort),a
+
+_ch3:
+  ld a,(PSGChannel3SFX)
+  or a
+  jr nz,_leave
+  ld a,(PSGChan3LowTone)                        ; restore channel 3 frequency
+  or PSGLatch|PSGChannel3
+  out (PSGDataPort),a
+  ld a,(PSGChan3Volume)                         ; restore channel 3 volume
+  and 0x0F
+  add a,l
+  cp 0x0F                                        ; check overflow
+  jr c,_psglib_anon_09                                        ; if it's <=15 then ok
+  ld a,0x0F                                      ; else, reset to 15
+_psglib_anon_09:or PSGLatch|PSGChannel3|PSGVolumeData
+  out (PSGDataPort),a
+
+_leave:
+  ld a,PSG_PLAYING
+  ld (PSGMusicStatus),a                         ; set status to PSG_PLAYING
+  ret
+
+; ************************************************************************************
+; sets the currently looping music to no more loops after the current
+; destroys AF
+PSGCancelLoop:
+  xor a
+  ld (PSGLoopFlag),a
+  ld (PSGLoopCounter),a
+  ret
+
+; ************************************************************************************
+; gets the current status of music into register A
+PSGGetStatus:
+  ld a,(PSGMusicStatus)
+  ret
+
+; ************************************************************************************
+; receives in L the volume attenuation for the music (0-15)
+; destroys AF
+PSGSetMusicVolumeAttenuation:
+  ld a,l
+  ld (PSGMusicVolumeAttenuation),a
+  ld a,(PSGMusicStatus)            ; if tune is not playing, leave
+  or a
+  ret z
+
+  ld a,(PSGChannel0SFX)            ; channel 0 busy with SFX?
+  or a
+  jr nz,_music_restore_channel1          ; if so, skip channel 0
+
+  ld a,(PSGChan0Volume)
+  and 0x0F
+  add a,l
+  cp 0x0F                           ; check overflow
+  jr c,_psglib_anon_10                           ; if it's <=15 then ok
+  ld a,0x0F                         ; else, reset to 15
+_psglib_anon_10:or PSGLatch|PSGChannel0|PSGVolumeData
+  out (PSGDataPort),a              ; output the byte
+
+_music_restore_channel1:
+  ld a,(PSGChannel1SFX)            ; channel 1 busy with SFX?
+  or a
+  jr nz,_music_restore_channel2          ; if so, skip channel 1
+
+  ld a,(PSGChan1Volume)
+  and 0x0F
+  add a,l
+  cp 0x0F                           ; check overflow
+  jr c,_psglib_anon_11                           ; if it's <=15 then ok
+  ld a,0x0F                         ; else, reset to 15
+_psglib_anon_11:or PSGLatch|PSGChannel1|PSGVolumeData
+  out (PSGDataPort),a              ; output the byte
+
+_music_restore_channel2:
+  ld a,(PSGChannel2SFX)            ; channel 2 busy with SFX?
+  or a
+  jr nz,_music_restore_channel3          ; if so, skip channel 2
+
+  ld a,(PSGChan2Volume)
+  and 0x0F
+  add a,l
+  cp 0x0F                           ; check overflow
+  jr c,_psglib_anon_12                           ; if it's <=15 then ok
+  ld a,0x0F                         ; else, reset to 15
+_psglib_anon_12:or PSGLatch|PSGChannel2|PSGVolumeData
+  out (PSGDataPort),a              ; output the byte
+
+_music_restore_channel3:
+  ld a,(PSGChannel3SFX)            ; channel 3 busy with SFX?
+  or a
+  ret nz                           ; if so, we're done
+
+  ld a,(PSGChan3Volume)
+  and 0x0F
+  add a,l
+  cp 0x0F                           ; check overflow
+  jr c,_psglib_anon_13                           ; if it's <=15 then ok
+  ld a,0x0F                         ; else, reset to 15
+_psglib_anon_13:or PSGLatch|PSGChannel3|PSGVolumeData
+  out (PSGDataPort),a              ; output the byte
+  ret
+
+; ************************************************************************************
+; receives in L the volume attenuation for the SFXs (0-15)
+; destroys AF
+PSGSetSFXVolumeAttenuation:
+  ld a,l
+  ld (PSGSFXVolumeAttenuation),a
+  ld a,(PSGSFXStatus)              ; if an SFX is not playing, leave
+  or a
+  ret z
+
+  ld a,(PSGChannel0SFX)            ; channel 0 used by SFX?
+  or a
+  jr z,_sfx_restore_channel1           ; if not, skip channel 0
+
+  ld a,(PSGSFXChan0Volume)
+  and 0x0F
+  add a,l
+  cp 0x0F                           ; check overflow
+  jr c,_psglib_anon_14                           ; if it's <=15 then ok
+  ld a,0x0F                         ; else, reset to 15
+_psglib_anon_14:or PSGLatch|PSGChannel0|PSGVolumeData
+  out (PSGDataPort),a              ; output the byte
+
+_sfx_restore_channel1:
+  ld a,(PSGChannel1SFX)            ; channel 1 used by SFX?
+  or a
+  jr z,_sfx_restore_channel2           ; if not, skip channel 1
+
+  ld a,(PSGSFXChan1Volume)
+  and 0x0F
+  add a,l
+  cp 0x0F                           ; check overflow
+  jr c,_psglib_anon_15                           ; if it's <=15 then ok
+  ld a,0x0F                         ; else, reset to 15
+_psglib_anon_15:or PSGLatch|PSGChannel1|PSGVolumeData
+  out (PSGDataPort),a              ; output the byte
+
+_sfx_restore_channel2:
+  ld a,(PSGChannel2SFX)            ; channel 2 used by SFX?
+  or a
+  jr z,_sfx_restore_channel3           ; if not, skip channel 2
+
+  ld a,(PSGSFXChan2Volume)
+  and 0x0F
+  add a,l
+  cp 0x0F                           ; check overflow
+  jr c,_psglib_anon_16                           ; if it's <=15 then ok
+  ld a,0x0F                         ; else, reset to 15
+_psglib_anon_16:or PSGLatch|PSGChannel2|PSGVolumeData
+  out (PSGDataPort),a              ; output the byte
+
+_sfx_restore_channel3:
+  ld a,(PSGChannel3SFX)            ; channel 3 used by SFX?
+  or a
+  ret z                            ; if not, we're done
+
+  ld a,(PSGSFXChan3Volume)
+  and 0x0F
+  add a,l
+  cp 0x0F                           ; check overflow
+  jr c,_psglib_anon_17                           ; if it's <=15 then ok
+  ld a,0x0F                         ; else, reset to 15
+_psglib_anon_17:or PSGLatch|PSGChannel3|PSGVolumeData
+  out (PSGDataPort),a              ; output the byte
+  ret
+
+; ************************************************************************************
+; sets all PSG channels to volume ZERO
+; destroys AF
+PSGSilenceChannels:
+  ld a,PSGLatch|PSGChannel0|PSGVolumeData|0x0F   ; latch channel 0, volume=0xF (silent)
+  out (PSGDataPort),a
+  ld a,PSGLatch|PSGChannel1|PSGVolumeData|0x0F   ; latch channel 1, volume=0xF (silent)
+  out (PSGDataPort),a
+  ld a,PSGLatch|PSGChannel2|PSGVolumeData|0x0F   ; latch channel 2, volume=0xF (silent)
+  out (PSGDataPort),a
+  ld a,PSGLatch|PSGChannel3|PSGVolumeData|0x0F   ; latch channel 3, volume=0xF (silent)
+  out (PSGDataPort),a
+  ret
+
+; ************************************************************************************
+; resets all PSG channels to previous volume
+; destroys AF,HL
+PSGRestoreVolumes:
+  ld a,(PSGChannel0SFX)            ; channel 0 busy with SFX?
+  jr nz,_restoreSFX0
+
+  ld a,(PSGMusicStatus)            ; check if tune is playing
+  or a
+  jr z,_chkchn1                    ; if not, skip channel 0
+
+  ld a,(PSGChan0Volume)
+  and 0x0F
+  ld hl,PSGMusicVolumeAttenuation
+  add a,(hl)
+  cp 0x0F                           ; check overflow
+  jr c,_write0                     ; if it's <=15 then ok
+  ld a,0x0F                         ; else, reset to 15
+  jp _write0
+
+_restoreSFX0:
+  ld a,(PSGSFXChan0Volume)
+  and 0x0F
+  ld hl,PSGSFXVolumeAttenuation
+  add a,(hl)
+  cp 0x0F                           ; check overflow
+  jr c,_write0                     ; if it's <=15 then ok
+  ld a,0x0F                         ; else, reset to 15
+
+_write0:
+  or PSGLatch|PSGChannel0|PSGVolumeData
+  out (PSGDataPort),a              ; output the byte
+
+_chkchn1:
+  ld a,(PSGChannel1SFX)            ; channel 1 busy with SFX?
+  jr nz,_restoreSFX1
+
+  ld a,(PSGMusicStatus)            ; check if tune is playing
+  or a
+  jr z,_chkchn2                    ; if not, skip channel 1
+
+  ld a,(PSGChan1Volume)
+  and 0x0F
+  ld hl,PSGMusicVolumeAttenuation
+  add a,(hl)
+  cp 0x0F                           ; check overflow
+  jr c,_write1                     ; if it's <=15 then ok
+  ld a,0x0F                         ; else, reset to 15
+  jp _write1
+
+_restoreSFX1:
+  ld a,(PSGSFXChan1Volume)
+  and 0x0F
+  ld hl,PSGSFXVolumeAttenuation
+  add a,(hl)
+  cp 0x0F                           ; check overflow
+  jr c,_write1                     ; if it's <=15 then ok
+  ld a,0x0F                         ; else, reset to 15
+
+_write1:
+  or PSGLatch|PSGChannel1|PSGVolumeData
+  out (PSGDataPort),a              ; output the byte
+
+_chkchn2:
+  ld a,(PSGChannel2SFX)            ; channel 2 busy with SFX?
+  jr nz,_restoreSFX2
+
+  ld a,(PSGMusicStatus)            ; check if tune is playing
+  or a
+  jr z,_chkchn3                    ; if not, skip chn2
+
+  ld a,(PSGChan2Volume)
+  and 0x0F
+  ld hl,PSGMusicVolumeAttenuation
+  add a,(hl)
+  cp 0x0F                           ; check overflow
+  jr c,_write2                     ; if it's <=15 then ok
+  ld a,0x0F                         ; else, reset to 15
+  jp _write2
+
+_restoreSFX2:
+  ld a,(PSGSFXChan2Volume)
+  and 0x0F
+  ld hl,PSGSFXVolumeAttenuation
+  add a,(hl)
+  cp 0x0F                           ; check overflow
+  jr c,_write2                     ; if it's <=15 then ok
+  ld a,0x0F                         ; else, reset to 15
+
+_write2:
+  or PSGLatch|PSGChannel2|PSGVolumeData
+  out (PSGDataPort),a              ; output the byte
+
+_chkchn3:
+  ld a,(PSGChannel3SFX)            ; channel 3 busy with SFX?
+  jr nz,_restoreSFX3
+
+  ld a,(PSGMusicStatus)            ; check if tune is playing
+  or a
+  ret z                            ; if not, we've done
+
+  ld a,(PSGChan3Volume)
+  and 0x0F
+  ld hl,PSGMusicVolumeAttenuation
+  add a,(hl)
+  cp 0x0F                           ; check overflow
+  jr c,_write3                     ; if it's <=15 then ok
+  ld a,0x0F                         ; else, reset to 15
+  jp _write3
+
+_restoreSFX3:
+  ld a,(PSGSFXChan3Volume)
+  and 0x0F
+  ld hl,PSGSFXVolumeAttenuation
+  add a,(hl)
+  cp 0x0F                           ; check overflow
+  jr c,_write3                     ; if it's <=15 then ok
+  ld a,0x0F                         ; else, reset to 15
+
+_write3:
+  or PSGLatch|PSGChannel3|PSGVolumeData
+  out (PSGDataPort),a              ; output the byte
+  ret
+
+; ************************************************************************************
+; receives in HL the address of the SFX PSG to start
+; receives in C the mask that indicates which channel(s) the SFX will use
+; destroys AF
+PSGSFXPlayLoop:
+  ld a,1                        ; SFX _IS_ a looping one
+  jp _psglib_anon_18
+PSGSFXPlay:
+  xor a                         ; SFX is _NOT_ a looping one
+_psglib_anon_18:ld (PSGSFXLoopFlag),a
+  call PSGSFXStop               ; if there's a SFX already playing, we should stop it!
+  ld (PSGSFXStart),hl           ; store begin of SFX
+  ld (PSGSFXPointer),hl         ; set the pointer to begin of SFX
+  ld (PSGSFXLoopPoint),hl       ; looppointer points to begin too
+  xor a
+  ld (PSGSFXSkipFrames),a       ; reset the skip frames
+  ld (PSGSFXSubstringLen),a     ; reset the substring len
+  bit 2,c                       ; channel 0 needed?
+  jr z,_psglib_anon_19
+  ld a,PSG_PLAYING
+  ld (PSGChannel0SFX),a
+_psglib_anon_19:bit 3,c                       ; channel 1 needed?
+  jr z,_psglib_anon_20
+  ld a,PSG_PLAYING
+  ld (PSGChannel1SFX),a
+_psglib_anon_20:bit 0,c                       ; channel 2 needed?
+  jr z,_psglib_anon_21
+  ld a,PSG_PLAYING
+  ld (PSGChannel2SFX),a
+_psglib_anon_21:bit 1,c                       ; channel 3 needed?
+  jr z,_psglib_anon_22
+  ld a,PSG_PLAYING
+  ld (PSGChannel3SFX),a
+_psglib_anon_22:ld (PSGSFXStatus),a           ; set SFXstatus to PSG_PLAYING if SFX uses at least one channel (0=PSG_STOPPED otherwise)
+  ld a,(PSGMusicStatus)         ; check if a tune is currently playing
+  or a
+  ret z                         ; if not, we've done
+
+  ld a,(PSGChan3LowTone)        ; test if music playing on channel 3 uses the frequency of channel 2
+  and 3
+  cp 3
+  ret nz                        ; if channel 3 doesn't use the frequency of channel 2 we're done
+
+  ld a,PSG_PLAYING
+  ld (PSGChannel3SFX),a         ; otherwise mark channel 3 as occupied by the SFX
+  ld a,PSGLatch|PSGChannel3|PSGVolumeData|0x0F   ; and silence channel 3
+  out (PSGDataPort),a
+  ret
+
+; ************************************************************************************
+; stops the SFX (leaving the music on, if it's playing)
+; destroys AF
+PSGSFXStop:
+  ld a,(PSGSFXStatus)            ; check status
+  or a
+  ret z                          ; no SFX playing, leave
+
+  ld a,(PSGChannel0SFX)          ; channel 0 playing?
+  or a
+  jr z,_psglib_anon_23
+  ld a,PSGLatch|PSGChannel0|PSGVolumeData|0x0F    ; latch channel 0, volume=0xF (silent)
+  out (PSGDataPort),a
+_psglib_anon_23:ld a,(PSGChannel1SFX)          ; channel 1 playing?
+  or a
+  jr z,_psglib_anon_24
+  ld a,PSGLatch|PSGChannel1|PSGVolumeData|0x0F    ; latch channel 1, volume=0xF (silent)
+  out (PSGDataPort),a
+_psglib_anon_24:ld a,(PSGChannel2SFX)          ; channel 2 playing?
+  or a
+  jr z,_psglib_anon_25
+  ld a,PSGLatch|PSGChannel2|PSGVolumeData|0x0F    ; latch channel 2, volume=0xF (silent)
+  out (PSGDataPort),a
+_psglib_anon_25:ld a,(PSGChannel3SFX)          ; channel 3 playing?
+  or a
+  jr z,_psglib_anon_26
+  ld a,PSGLatch|PSGChannel3|PSGVolumeData|0x0F    ; latch channel 3, volume=0xf (silent)
+  out (PSGDataPort),a
+_psglib_anon_26:ld a,(PSGMusicStatus)          ; check if a tune is playing
+  or a
+  jp z,_skipRestore              ; if it's not playing, skip restoring PSG values
+
+  ld a,(PSGChannel0SFX)          ; channel 0 playing?
+  or a
+  jr z,_skip_chn0
+  ld a,(PSGChan0LowTone)
+  and 0x0F                        ; use only low 4 bits of byte
+  or PSGLatch|PSGChannel0        ; latch channel 0, low part of tone
+  out (PSGDataPort),a
+  ld a,(PSGChan0HighTone)        ; high part of tone (latched channel 0, tone)
+  and 0x3F                        ; use only low 6 bits of byte
+  out (PSGDataPort),a
+  ld a,(PSGChan0Volume)          ; restore music' channel 0 volume
+  and 0x0F                        ; use only low 4 bits of byte
+  push bc
+    ld b,a                            ; save it temporary
+    ld a,(PSGMusicVolumeAttenuation)  ;
+    add a,b
+    cp 0x0F                            ; check overflow
+    jr c,_psglib_anon_27                            ; if it's <=15 then ok
+    ld a,0x0F                          ; else, reset to 15
+_psglib_anon_27:  or PSGLatch|PSGChannel0|PSGVolumeData
+    out (PSGDataPort),a              ; output the byte
+  pop bc
+
+_skip_chn0:
+  ld a,(PSGChannel1SFX)          ; channel 1 playing?
+  or a
+  jr z,_skip_chn1
+  ld a,(PSGChan1LowTone)
+  and 0x0F                        ; use only low 4 bits of byte
+  or PSGLatch|PSGChannel1        ; latch channel 1, low part of tone
+  out (PSGDataPort),a
+  ld a,(PSGChan1HighTone)        ; high part of tone (latched channel 1, tone)
+  and 0x3F                        ; use only low 6 bits of byte
+  out (PSGDataPort),a
+  ld a,(PSGChan1Volume)          ; restore music' channel 1 volume
+  and 0x0F                        ; use only low 4 bits of byte
+  push bc
+    ld b,a                            ; save it temporary
+    ld a,(PSGMusicVolumeAttenuation)  ;
+    add a,b
+    cp 0x0F                            ; check overflow
+    jr c,_psglib_anon_28                            ; if it's <=15 then ok
+    ld a,0x0F                          ; else, reset to 15
+_psglib_anon_28:  or PSGLatch|PSGChannel1|PSGVolumeData
+    out (PSGDataPort),a              ; output the byte
+  pop bc
+
+_skip_chn1:
+  ld a,(PSGChannel2SFX)          ; channel 2 playing?
+  or a
+  jr z,_skip_chn2
+  ld a,(PSGChan2LowTone)
+  and 0x0F                        ; use only low 4 bits of byte
+  or PSGLatch|PSGChannel2        ; latch channel 2, low part of tone
+  out (PSGDataPort),a
+  ld a,(PSGChan2HighTone)        ; high part of tone (latched channel 2, tone)
+  and 0x3F                        ; use only low 6 bits of byte
+  out (PSGDataPort),a
+  ld a,(PSGChan2Volume)          ; restore music' channel 2 volume
+  and 0x0F                        ; use only low 4 bits of byte
+  push bc
+    ld b,a                            ; save it temporary
+    ld a,(PSGMusicVolumeAttenuation)  ;
+    add a,b
+    cp 0x0F                            ; check overflow
+    jr c,_psglib_anon_29                            ; if it's <=15 then ok
+    ld a,0x0F                          ; else, reset to 15
+_psglib_anon_29:  or PSGLatch|PSGChannel2|PSGVolumeData
+    out (PSGDataPort),a              ; output the byte
+  pop bc
+
+_skip_chn2:
+  ld a,(PSGChannel3SFX)          ; channel 3 playing?
+  or a
+  jr z,_skip_chn3
+  ld a,(PSGChan3LowTone)
+  and 0x07                        ; use only low 3 bits of byte
+  or PSGLatch|PSGChannel3        ; latch channel 3, low part of tone (no high part)
+  out (PSGDataPort),a
+  ld a,(PSGChan3Volume)          ; restore music' channel 3 volume
+  and 0x0F                        ; use only low 4 bits of byte
+  push bc
+    ld b,a                            ; save it temporary
+    ld a,(PSGMusicVolumeAttenuation)  ;
+    add a,b
+    cp 0x0F                            ; check overflow
+    jr c,_psglib_anon_30                            ; if it's <=15 then ok
+    ld a,0x0F                          ; else, reset to 15
+_psglib_anon_30:  or PSGLatch|PSGChannel3|PSGVolumeData
+    out (PSGDataPort),a              ; output the byte
+  pop bc
+_skip_chn3:
+  xor a                          ; ld a,PSG_STOPPED
+_skipRestore:
+  ld (PSGChannel0SFX),a
+  ld (PSGChannel1SFX),a
+  ld (PSGChannel2SFX),a
+  ld (PSGChannel3SFX),a
+  ld (PSGSFXStatus),a            ; set status to PSG_STOPPED
+  ret
+
+; ************************************************************************************
+; sets the currently looping SFX to no more loops after the current
+; destroys AF
+PSGSFXCancelLoop:
+  xor a
+  ld (PSGSFXLoopFlag),a
+  ret
+
+; ************************************************************************************
+; gets the current SFX status into register A
+PSGSFXGetStatus:
+  ld a,(PSGSFXStatus)
+  ret
+
+; ************************************************************************************
+; processes a music frame
+; destroys AF,HL,BC
+PSGFrame:
+  ld a,(PSGMusicStatus)          ; check if we have got to play a tune
+  or a
+  ret z
+
+  ld a,(PSGMusicSkipFrames)      ; check if we havve got to skip frames
+  or a
+  jp nz,_skipFrame
+
+  ld hl,(PSGMusicPointer)        ; read current address
+
+_intLoop:
+  ld b,(hl)                      ; load PSG byte (in B)
+  inc hl                         ; point to next byte
+  ld a,(PSGMusicSubstringLen)    ; read substring len
+  or a
+  jr z,_continue                 ; check if it is 0 (we are not in a substring)
+  dec a                          ; decrease len
+  ld (PSGMusicSubstringLen),a    ; save len
+  jr nz,_continue
+  ld hl,(PSGMusicSubstringRetAddr)  ; substring is over, retrieve return address
+
+_continue:
+  ld a,b                         ; copy PSG byte into A
+  cp PSGLatch                    ; is it a latch?
+  jr c,_noLatch                  ; if < 0x80 then it is NOT a latch
+  ld (PSGMusicLastLatch),a       ; it is a latch - save it in "LastLatch"
+
+  ; we have got the latch PSG byte both in A and in B
+  ; and we have to check if the value should pass to PSG or not
+  bit 4,a                        ; test if it is a volume
+  jr nz,_latch_Volume            ; jump if volume data
+  bit 6,a                        ; test if the latch it is for channels 0-1 or for 2-3
+  jp nz,_latch_chn23             ; jump if it is for channels 2-3
+
+  ; we have got the latch (tone, chn 0 or 1) PSG byte both in A and in B
+  ; and we have to check if the value should be passed to PSG or not
+  bit 5,a                        ; test if tone it is for channel 0 or 1
+  jr z,_ifchn0                   ; jump if channel 0
+  ld (PSGChan1LowTone),a         ; save tone LOW data
+  ld a,(PSGChannel1SFX)          ; channel 1 available for music?
+  or a
+  jr z,_send2PSG_B               ; then send data
+  jp _intLoop
+_ifchn0:
+  ld (PSGChan0LowTone),a         ; save tone LOW data
+  ld a,(PSGChannel0SFX)          ; channel 0 available for music?
+  or a
+  jr z,_send2PSG_B               ; then send data
+  jp _intLoop
+
+_latch_chn23:
+  ; we have got the latch (tone, chn 2 or 3) PSG byte both in A and in B
+  ; and we have to check if the value should be passed to PSG or not
+  bit 5,a                        ; test if tone it is for channel 2 or 3
+  jr z,_ifchn2                   ; jump if channel 2
+  ld (PSGChan3LowTone),a         ; save tone LOW data
+  ld a,(PSGChannel3SFX)          ; channel 3 available for music?
+  or a
+  jp nz,_intLoop
+  ld a,(PSGChan3LowTone)
+  and 3                          ; test if channel 3 is set to use the frequency of channel 2
+  cp 3
+  jr nz,_send2PSG_B              ; if channel 3 does not use frequency of channel 2 jump
+  ld a,(PSGChannel2SFX)          ; test if an SFX is playing on channel 2
+  or a
+  jr z,_send2PSG_B               ; if no SFX is playing on channel 2 jump
+  ld (PSGChannel3SFX),a          ; otherwise mark channel 3 as occupied
+  ld a,PSGLatch|PSGChannel3|PSGVolumeData|0x0F   ; and silence channel 3
+  out (PSGDataPort),a
+  jp _intLoop
+_ifchn2:
+  ld (PSGChan2LowTone),a         ; save tone LOW data
+  ld a,(PSGChannel2SFX)          ; channel 2 available for music?
+  or a
+  jr z,_send2PSG_B
+  jp _intLoop
+
+_noLatch:
+  cp PSGData
+  jr c,_command                  ; if < 0x40 then it is a command
+  ; it's a data
+  ld a,(PSGMusicLastLatch)       ; retrieve last latch
+  jp _output_NoLatch
+
+_latch_Volume:
+  bit 6,a                        ; test if the latch it is for channels 0-1 or for 2-3
+  jr nz,_latch_Volume_23         ; volume is for channel 2 or 3
+  bit 5,a                        ; test if volume it is for channel 0 or 1
+  jr z,_ifchn0v                  ; jump for channel 0
+  ld (PSGChan1Volume),a          ; save volume data
+  ld a,(PSGChannel1SFX)          ; channel 1 available for music?
+  or a
+  jr z,_sendVolume2PSG_B
+  jp _intLoop
+_ifchn0v:
+  ld (PSGChan0Volume),a          ; save volume data
+  ld a,(PSGChannel0SFX)          ; channel 0 available for music?
+  or a
+  jr z,_sendVolume2PSG_B
+  jp _intLoop
+
+_send2PSG_B:
+  ld a,b
+_send2PSG_A:
+  out (PSGDataPort),a            ; output the byte
+  jp _intLoop
+
+_latch_Volume_23:
+  bit 5,a                        ; test if volume it is for channel 2 or 3
+  jr z,_chn2                     ; jump for channel 2
+  ld (PSGChan3Volume),a          ; save volume data
+  ld a,(PSGChannel3SFX)          ; channel 3 available for music?
+  or a
+  jr z,_sendVolume2PSG_B
+  jp _intLoop
+_chn2:
+  ld (PSGChan2Volume),a          ; save volume data
+  ld a,(PSGChannel2SFX)          ; channel 2 available for music?
+  or a
+  jr z,_sendVolume2PSG_B
+  jp _intLoop
+
+_skipFrame:
+  dec a
+  ld (PSGMusicSkipFrames),a
+  ret
+
+_command:
+  cp PSGWait
+  jr z,_done                     ; no additional frames
+  jr c,_otherCommands            ; other commands?
+  and 0x07                        ; take only the last 3 bits for skip frames
+  ld (PSGMusicSkipFrames),a      ; we got additional frames
+_done:
+  ld (PSGMusicPointer),hl        ; save current address
+  ret                            ; frame done
+
+_otherCommands:
+  cp PSGSubString
+  jr nc,_substring
+  cp PSGEnd
+  jr z,_musicLoop
+  cp PSGLoop
+  jr z,_setLoopPoint
+
+  ; ***************************************************************************
+  ; we should never get here!
+  ; if we do, it means the PSG file is probably corrupted, so we just RET
+  ; ***************************************************************************
+
+  ret
+
+_sendVolume2PSG_B:
+  ld a,b
+_sendVolume2PSG_A:
+  ld c,a                           ; save the PSG command byte
+  and 0x0F                          ; keep lower nibble
+  ld b,a                           ; save value
+  ld a,(PSGMusicVolumeAttenuation) ; load volume attenuation
+  add a,b                          ; add value
+  cp 0x0F                           ; check overflow
+  jr c,_no_overflow                ; if it is <=15 then ok
+  ld a,0x0F                         ; else, reset to 15
+_no_overflow:
+  ld b,a                           ; save new attenuated volume value
+  ld a,c                           ; retrieve PSG command
+  and 0xF0                          ; keep upper nibble
+  or b                             ; set attenuated volume
+  out (PSGDataPort),a              ; output the byte
+  jp _intLoop
+
+_output_NoLatch:
+  ; we got the last latch in A and the PSG data in B
+  ; and we have to check if the value should pass to PSG or not
+  ; note that non-latch commands can be only contain frequencies (no volumes)
+  ; for channels 0,1,2 only (no noise)
+  bit 6,a                        ; test if the latch it is for channels 0-1 or for chn 2
+  jr nz,_high_part_Tone_ch2      ; it is tone data for channel 2
+
+  bit 5,a                        ; test if latch is for channel 0 or 1
+  jr nz,_high_part_Tone_ch1      ; it is tone data for channel 1
+
+  ; we got the last latch in A and the PSG data in B
+  ; and we have to check if the value should pass to PSG or not
+  ld a,b                         ; move PSG data in A
+  ld (PSGChan0HighTone),a        ; save channel 0 tone HIGH data
+  ld a,(PSGChannel0SFX)          ; channel 0 available for music?
+  or a
+  jr z,_send2PSG_B
+  jp _intLoop
+
+_high_part_Tone_ch1:
+  ; we got the last latch in A and the PSG data in B
+  ; and we have to check if the value should pass to PSG or not
+  ld a,b                         ; move PSG data in A
+  ld (PSGChan1HighTone),a        ; save channel 1 tone HIGH data
+  ld a,(PSGChannel1SFX)          ; channel 1 available for music?
+  or a
+  jr z,_send2PSG_B
+  jp _intLoop
+
+_high_part_Tone_ch2:
+  ; we got the last latch in A and the PSG data in B
+  ; and we have to check if the value should pass to PSG or not
+  ; PSG data can only be for channel 2, here
+  ld a,b                         ; move PSG data in A
+  ld (PSGChan2HighTone),a        ; save channel 2 tone HIGH data
+  ld a,(PSGChannel2SFX)          ; channel 2 available for music
+  or a
+  jp z,_send2PSG_B               ; TOO FAR for JR here :|
+  jp _intLoop
+
+_setLoopPoint:
+  ld (PSGMusicLoopPoint),hl
+  jp _intLoop
+
+_musicLoop:
+  ld hl,(PSGMusicLoopPoint)
+  ld a,(PSGLoopFlag)               ; infinite loop requested?
+  or a
+  jp nz,_intLoop                   ; Yes: do loop
+  ld a,(PSGLoopCounter)            ; one more loop requested?
+  or a
+  jp z,PSGStop                     ; No: stop the music! (tail call optimization)
+  dec a
+  ld (PSGLoopCounter),a            ; decrement loop counter
+  jp _intLoop                      ; do loop
+
+_substring:
+  sub PSGSubString-4                  ; len is value - 0x08 + 4
+  ld (PSGMusicSubstringLen),a         ; save len
+  ld c,(hl)                           ; load substring address (offset)
+  inc hl
+  ld b,(hl)
+  inc hl
+  ld (PSGMusicSubstringRetAddr),hl    ; save return address
+  ld hl,(PSGMusicStart)
+  add hl,bc                           ; make substring current
+  jp _intLoop
+
+; ************************************************************************************
+; processes a SFX frame
+; destroys AF,HL,BC
+PSGSFXFrame:
+  ld a,(PSGSFXStatus)            ; check if we have got to play SFX
+  or a
+  ret z
+
+  ld a,(PSGSFXSkipFrames)        ; check if we have got to skip frames
+  or a
+  jp nz,_skipSFXFrame
+
+  ld hl,(PSGSFXPointer)          ; read current SFX address
+
+_intSFXLoop:
+  ld b,(hl)                      ; load a byte in B, temporary
+  inc hl                         ; point to next byte
+  ld a,(PSGSFXSubstringLen)      ; read substring len
+  or a                           ; check if it is 0 (we are not in a substring)
+  jr z,_SFXcontinue
+  dec a                          ; decrease len
+  ld (PSGSFXSubstringLen),a      ; save len
+  jr nz,_SFXcontinue
+  ld hl,(PSGSFXSubstringRetAddr) ; substring over, retrieve return address
+
+_SFXcontinue:
+  ld a,b                         ; restore byte
+  cp PSGData
+  jp c,_SFXcommand               ; if less than 0x40 then it is a command
+  bit 7,a                        ; check if it is a latch
+  jr z,_SFXoutbyte               ; if not, output it directly
+  bit 4,a                        ; check if it is a volume byte
+  jr z,_SFXoutbyte               ; if not, output it directly
+
+  bit 6,a                        ; check if it is volume for channels 0-1 or for 2-3
+  jr nz,_SFXchn23
+
+  bit 5,a                        ; check if it is volume for channel 0 or channel 1
+  jr nz,_SFXvolumechn1
+  ld (PSGSFXChan0Volume),a
+  jr _SFXoutvolume
+
+_SFXvolumechn1:
+  ld (PSGSFXChan1Volume),a
+  jr _SFXoutvolume
+
+_SFXchn23:
+  bit 5,a                        ; check if it is volume for channel 2 or channel 3
+  jr nz,_SFXvolumechn3
+  ld (PSGSFXChan2Volume),a
+  jr _SFXoutvolume
+
+_SFXvolumechn3:
+  ld (PSGSFXChan3Volume),a
+
+_SFXoutvolume:
+  and 0x0F                        ; keep lower nibble
+  ld c,a                         ; save value
+  ld a,(PSGSFXVolumeAttenuation) ; load volume attenuation
+  add a,c                        ; add value
+  cp 0x0F                         ; check overflow
+  jr c,_no_overflow_SFX          ; if it is <=15 then ok
+  ld a,0x0F                       ; else, reset to 15
+_no_overflow_SFX:
+  ld c,a                         ; save new attenuated volume value
+  ld a,b                         ; retrieve original PSG command
+  and 0xF0                        ; keep upper nibble (channel+volume bits)
+  or c                           ; set attenuated SFX volume
+_SFXoutbyte:
+  out (PSGDataPort),a            ; output the byte
+  jp _intSFXLoop
+
+_skipSFXFrame:
+  dec a
+  ld (PSGSFXSkipFrames),a
+  ret
+
+_SFXcommand:
+  cp PSGWait
+  jr z,_SFXdone                  ; no additional frames
+  jr c,_SFXotherCommands         ; other commands?
+  and 0x07                        ; take only the last 3 bits for skip frames
+  ld (PSGSFXSkipFrames),a        ; we got additional frames to skip
+_SFXdone:
+  ld (PSGSFXPointer),hl          ; save current address
+  ret                            ; frame done
+
+_SFXotherCommands:
+  cp PSGSubString
+  jr nc,_SFXsubstring
+  cp PSGEnd
+  jr z,_sfxLoop
+  cp PSGLoop
+  jr z,_SFXsetLoopPoint
+
+  ; ***************************************************************************
+  ; we should never get here!
+  ; if we do, it means the PSG SFX file is probably corrupted, so we just RET
+  ; ***************************************************************************
+
+  ret
+
+_SFXsetLoopPoint:
+  ld (PSGSFXLoopPoint),hl
+  jp _intSFXLoop
+
+_sfxLoop:
+  ld a,(PSGSFXLoopFlag)               ; is it a looping SFX?
+  or a
+  jp z,PSGSFXStop                     ; No:stop it! (tail call optimization)
+  ld hl,(PSGSFXLoopPoint)
+  ld (PSGSFXPointer),hl
+  jp _intSFXLoop
+
+_SFXsubstring:
+  sub PSGSubString-4                  ; len is value - 0x08 + 4
+  ld (PSGSFXSubstringLen),a           ; save len
+  ld c,(hl)                           ; load substring address (offset)
+  inc hl
+  ld b,(hl)
+  inc hl
+  ld (PSGSFXSubstringRetAddr),hl    ; save return address
+  ld hl,(PSGSFXStart)
+  add hl,bc                         ; make substring current
+  jp _intSFXLoop
+
+; PSGlib workspace in the RAM reserved by the SN76489 application.
+PSGLIB_RAM_START            .equ STACK_TOP+1
+  ; fundamental vars
+PSGMusicStatus                 .equ PSGLIB_RAM_START+0x00    ; are we playing a background music?
+PSGMusicStart                  .equ PSGLIB_RAM_START+0x01    ; the pointer to the beginning of music
+PSGMusicPointer                .equ PSGLIB_RAM_START+0x03    ; the pointer to the current
+PSGMusicLoopPoint              .equ PSGLIB_RAM_START+0x05    ; the pointer to the loop begin
+PSGMusicSkipFrames             .equ PSGLIB_RAM_START+0x07    ; the frames we need to skip
+PSGLoopFlag                    .equ PSGLIB_RAM_START+0x08    ; the tune should loop forever or not (flag)
+PSGLoopCounter                 .equ PSGLIB_RAM_START+0x09    ; how many times the tune should loop
+PSGMusicLastLatch              .equ PSGLIB_RAM_START+0x0a    ; the last PSG music latch
+
+  ; decompression vars
+PSGMusicSubstringLen           .equ PSGLIB_RAM_START+0x0b    ; lenght of the substring we are playing
+PSGMusicSubstringRetAddr       .equ PSGLIB_RAM_START+0x0c    ; return to this address when substring is over
+
+  ; command buffers
+PSGChan0Volume                 .equ PSGLIB_RAM_START+0x0e       ; the volume for channel 0
+PSGChan1Volume                 .equ PSGLIB_RAM_START+0x0f       ; the volume for channel 1
+PSGChan2Volume                 .equ PSGLIB_RAM_START+0x10       ; the volume for channel 2
+PSGChan3Volume                 .equ PSGLIB_RAM_START+0x11       ; the volume for channel 3
+
+PSGChan0LowTone                .equ PSGLIB_RAM_START+0x12       ; the low tone bits for channels 0
+PSGChan1LowTone                .equ PSGLIB_RAM_START+0x13       ; the low tone bits for channels 1
+PSGChan2LowTone                .equ PSGLIB_RAM_START+0x14       ; the low tone bits for channels 2
+PSGChan3LowTone                .equ PSGLIB_RAM_START+0x15       ; the low tone bits for channels 3
+PSGChan0HighTone               .equ PSGLIB_RAM_START+0x16       ; the high tone bits for channel 0
+PSGChan1HighTone               .equ PSGLIB_RAM_START+0x17       ; the high tone bits for channel 1
+PSGChan2HighTone               .equ PSGLIB_RAM_START+0x18       ; the high tone bits for channel 2
+
+PSGMusicVolumeAttenuation      .equ PSGLIB_RAM_START+0x19       ; the volume attenuation applied to the tune (0-15)
+
+  ; ******* SFX *************
+
+  ; flags for SFX channels usage
+PSGChannel0SFX                 .equ PSGLIB_RAM_START+0x1a       ; !0 means channel 0 is allocated to SFX
+PSGChannel1SFX                 .equ PSGLIB_RAM_START+0x1b       ; !0 means channel 1 is allocated to SFX
+PSGChannel2SFX                 .equ PSGLIB_RAM_START+0x1c       ; !0 means channel 2 is allocated to SFX
+PSGChannel3SFX                 .equ PSGLIB_RAM_START+0x1d       ; !0 means channel 3 is allocated to SFX
+
+  ; command buffers for SFX
+PSGSFXChan0Volume              .equ PSGLIB_RAM_START+0x1e       ; the volume for channel 0
+PSGSFXChan1Volume              .equ PSGLIB_RAM_START+0x1f       ; the volume for channel 1
+PSGSFXChan2Volume              .equ PSGLIB_RAM_START+0x20       ; the volume for channel 2
+PSGSFXChan3Volume              .equ PSGLIB_RAM_START+0x21       ; the volume for channel 3
+
+PSGSFXVolumeAttenuation        .equ PSGLIB_RAM_START+0x22       ; the volume attenuation applied to the SFX (0-15)
+
+  ; fundamental vars for SFX
+PSGSFXStatus                   .equ PSGLIB_RAM_START+0x23       ; are we playing a SFX?
+PSGSFXStart                    .equ PSGLIB_RAM_START+0x24       ; the pointer to the beginning of SFX
+PSGSFXPointer                  .equ PSGLIB_RAM_START+0x26       ; the pointer to the current address
+PSGSFXLoopPoint                .equ PSGLIB_RAM_START+0x28       ; the pointer to the loop begin
+PSGSFXSkipFrames               .equ PSGLIB_RAM_START+0x2a       ; the frames we need to skip
+PSGSFXLoopFlag                 .equ PSGLIB_RAM_START+0x2b       ; the SFX should loop or not (flag)
+
+  ; decompression vars for SFX
+PSGSFXSubstringLen             .equ PSGLIB_RAM_START+0x2c       ; lenght of the substring we are playing
+PSGSFXSubstringRetAddr         .equ PSGLIB_RAM_START+0x2d       ; return to this address when substring is over
+PSGLIB_RAM_SIZE                .equ 0x2f
+#assert PSGLIB_RAM_START+PSGLIB_RAM_SIZE <= SAVED_SP
diff --git a/bios.asm b/bios.asm
index 434c328..bf272f1 100644
--- a/bios.asm
+++ b/bios.asm
@@ -145,6 +145,7 @@ init:
     ei
 
     call        tape_init
+    call        psg_silence
 
     ; Print header message
     ld          hl,msg_header
@@ -272,6 +273,13 @@ release_daisy_chain:
 ctc_uart_init:
     ; Reset CTC channels
     ld          a,003h
+    ; A channel may still be waiting for a time constant after a warm boot.
+    ; In that state the first byte is consumed as the constant, so send the
+    ; reset control word again to guarantee the unused channel is disabled.
+    out         (CTC_CHANNEL_0),a
+    out         (CTC_CHANNEL_1),a
+    out         (CTC_CHANNEL_2),a
+    out         (CTC_CHANNEL_3),a
     out         (CTC_CHANNEL_0),a
     out         (CTC_CHANNEL_1),a
     out         (CTC_CHANNEL_2),a
@@ -557,6 +565,20 @@ delay_ms:
     jp          nz,1$           ; 10T
     ret
 
+; -------------------------------------------------------
+; Silence all audio generators
+; -------------------------------------------------------
+psg_silence:
+    ld a,0x9f       ; mute tone 0
+    out (SN_PORT),a
+    ld a,0xbf       ; mute tone 1
+    out (SN_PORT),a
+    ld a,0xdf       ; mute tone 2
+    out (SN_PORT),a
+    ld a,0xff       ; mute noise
+    out (SN_PORT),a
+    ret
+
 ; -------------------------------------------------------
 ; Strings
 ; -------------------------------------------------------
diff --git a/hardware.inc b/hardware.inc
index 11b9da7..b00b2a6 100644
--- a/hardware.inc
+++ b/hardware.inc
@@ -6,3 +6,4 @@ BANK_ENABLE_BIT                 .equ 004h
 BANK_MODE_CLEAR_MASK            .equ 0f9h
 
 TAPE_PORT                       .equ 018h
+SN_PORT                         .equ 019h
\ No newline at end of file
diff --git a/hardware/CUPL.PLD b/hardware/CUPL.PLD
deleted file mode 100644
index 1668645..0000000
--- a/hardware/CUPL.PLD
+++ /dev/null
@@ -1,199 +0,0 @@
-Name     casette;
-PartNo   00;
-Date     2026-10-03;
-Revision 01;
-Designer joppe;
-Company  unknown;
-Assembly None;
-Location unknown;
-Device   g22v10;
-
-
-/* ------------------------------------------------------------
-   Constants
-   ------------------------------------------------------------ */
-
-ar = 'b'0;
-sp = 'b'0;
-
-
-/* ------------------------------------------------------------
-   Pin assignments
-
-   Physical signals IOSEL, RD and WR are active-low.
-   Their polarity is expressed in the equations with !.
-   ------------------------------------------------------------ */
-
-/* inputs */
-
-PIN 1 = CLK;
-
-PIN 2 = A1;
-PIN 3 = A2;
-
-PIN 4 = IOSEL;
-PIN 5 = RD;
-PIN 6 = A0;
-
-PIN 7 = COMP;
-PIN 8 = WR;
-
-
-/* data bus */
-
-PIN 14 = D0;
-PIN 15 = D1;
-PIN 16 = D2;
-PIN 17 = D3;
-PIN 18 = D4;
-PIN 19 = D5;
-PIN 20 = D6;
-PIN 21 = D7;
-
-
-/* registered output */
-
-PIN 22 = LED;
-
-
-/* ------------------------------------------------------------
-   Read register at offset 0
-
-   Conditions:
-
-       /IOSEL = 0
-       /RD    = 0
-       /WR    = 1
-       A2:A0  = 000
-
-   Result:
-
-       D0     = COMP
-       D7..D1 = 0
-   ------------------------------------------------------------ */
-
-D0 = COMP;
-
-D1 = 'b'0;
-D2 = 'b'0;
-D3 = 'b'0;
-D4 = 'b'0;
-D5 = 'b'0;
-D6 = 'b'0;
-D7 = 'b'0;
-
-
-D0.OE =
-      !IOSEL
-    & !RD
-    &  WR
-    & !A2
-    & !A1
-    & !A0;
-
-D1.OE =
-      !IOSEL
-    & !RD
-    &  WR
-    & !A2
-    & !A1
-    & !A0;
-
-D2.OE =
-      !IOSEL
-    & !RD
-    &  WR
-    & !A2
-    & !A1
-    & !A0;
-
-D3.OE =
-      !IOSEL
-    & !RD
-    &  WR
-    & !A2
-    & !A1
-    & !A0;
-
-D4.OE =
-      !IOSEL
-    & !RD
-    &  WR
-    & !A2
-    & !A1
-    & !A0;
-
-D5.OE =
-      !IOSEL
-    & !RD
-    &  WR
-    & !A2
-    & !A1
-    & !A0;
-
-D6.OE =
-      !IOSEL
-    & !RD
-    &  WR
-    & !A2
-    & !A1
-    & !A0;
-
-D7.OE =
-      !IOSEL
-    & !RD
-    &  WR
-    & !A2
-    & !A1
-    & !A0;
-
-
-/* ------------------------------------------------------------
-   Writable LED register
-
-   Write conditions:
-
-       /IOSEL = 0
-       /RD    = 1
-       /WR    = 0
-       A2:A0  = 000
-
-   During such a write:
-
-       LED.D = D0
-
-   Otherwise:
-
-       LED.D = LED
-
-   Pin 1 (CLK) clocks the registered macrocell.
-   ------------------------------------------------------------ */
-
-LED.D =
-      (
-          !IOSEL
-        &  RD
-        & !WR
-        & !A2
-        & !A1
-        & !A0
-        &  D0
-      )
-
-    #
-
-      (
-          (
-              IOSEL
-            # !RD
-            #  WR
-            #  A2
-            #  A1
-            #  A0
-          )
-        & LED
-      );
-
-
-LED.ar = ar;
-LED.sp = sp;
\ No newline at end of file
diff --git a/hardware/acc.jed b/hardware/acc.jed
new file mode 100644
index 0000000..97c29af
--- /dev/null
+++ b/hardware/acc.jed
@@ -0,0 +1,49 @@
+
+CUPL(WM)        5.0a  Serial# MW-10400000
+Device          g22v10  Library DLIB-h-40-1
+Created         Sat Oct 17 12:42:37 2026
+Name            acc
+Partno          00
+Revision        01
+Date            2026-10-11
+Designer        Joppe Blondel
+Company         unknown
+Assembly        unknown
+Location        unknown
+*QP24 
+*QF5892 
+*G0 
+*F0 
+*L00416 00000000000000000000000011111111
+*L00448 11111111111111111111111111111111
+*L00480 11111111101110111011011110111111
+*L00512 10111111110111111111111011110111
+*L00544 11111111111111111111111111111111
+*L00576 11101111111110111111111111111111
+*L00608 11111111111111101111111111111111
+*L00640 11110111111111111111111111101111
+*L00672 11111111011111111111111111111111
+*L00704 11110110111111111111111111111111
+*L00736 11111111111111111110011111111111
+*L00768 11111111111111111111111100000000
+*L03648 00001111111111111111111111111111
+*L03680 11111111111111111111011110111011
+*L03712 10111011111101111111111111111111
+*L03744 01111011101101110111111110111111
+*L03776 11111111000000000000000000000000
+*L04288 00000000000000000000000011111111
+*L04320 11111111111111111111111111111111
+*L04352 11111111011110111011011111111111
+*L04384 10111111111111110000000000000000
+*L04864 00000000000000000000111111111111
+*L04896 11111111111111111111111111111111
+*L04928 11111011101110110111011111111011
+*L04960 11111111111100000000000000000000
+*L05344 00000000000000000000000011111011
+*L05376 10111011101110111111011111111111
+*L05408 11111111111111111111111111110111
+*L05440 11111111111111110000000000000000
+*L05792 00000000000000000010000000001111
+*L05824 01110011000000110000000000000000
+*C5C1A
+*46C6
\ No newline at end of file
diff --git a/hardware/audio_casette_card.abs b/hardware/audio_casette_card.abs
new file mode 100644
index 0000000..252c450
Binary files /dev/null and b/hardware/audio_casette_card.abs differ
diff --git a/hardware/audio_casette_card.doc b/hardware/audio_casette_card.doc
new file mode 100644
index 0000000..d567d1c
--- /dev/null
+++ b/hardware/audio_casette_card.doc
@@ -0,0 +1,297 @@
+
+*******************************************************************************
+                                      acc
+*******************************************************************************
+
+CUPL(WM)        5.0a Serial# MW-10400000
+Device          g22v10  Library DLIB-h-40-1
+Created         Sat Oct 17 12:42:37 2026
+Name            acc
+Partno          00
+Revision        01
+Date            2026-10-11
+Designer        Joppe Blondel
+Company         unknown
+Assembly        unknown
+Location        unknown
+
+===============================================================================
+                            Expanded Product Terms
+===============================================================================
+
+AYADDRWRITE =>
+    A0 & A1 & !A2 & !IOSELN & RDN & !WRN
+
+AYBC1 =>
+    !A0 & A1 & !A2 & !IOSELN & !RDN & WRN
+  # A0 & A1 & !A2 & !IOSELN & RDN & !WRN
+
+AYBDIR =>
+    A1 & !A2 & !IOSELN & RDN & !WRN
+
+AYDATAREAD =>
+    !A0 & A1 & !A2 & !IOSELN & !RDN & WRN
+
+AYDATAWRITE =>
+    !A0 & A1 & !A2 & !IOSELN & RDN & !WRN
+
+COUT.d  =>
+    !A0 & !A1 & !A2 & D0 & !IOSELN & RDN & !WRN
+  # COUT & IOSELN
+  # COUT & !RDN
+  # COUT & WRN
+  # A0 & COUT
+  # A1 & COUT
+  # A2 & COUT
+
+COUT.ar  =>
+    0 
+
+COUT.sp  =>
+    0 
+
+D0 =>
+    COMP
+
+D0.oe  =>
+    !A0 & !A1 & !A2 & !IOSELN & !RDN & WRN
+
+SNWEN =>
+    A0 & !A1 & !A2 & !IOSELN & RDN & !WRN
+
+ar =>
+    0 
+
+sp =>
+    0 
+
+AYBC1.oe  =>
+    1 
+
+AYBDIR.oe  =>
+    1 
+
+COUT.oe  =>
+    1 
+
+SNWEN.oe  =>
+    1 
+
+
+===============================================================================
+                                 Symbol Table
+===============================================================================
+
+Pin Variable                                    Pterms   Max     Min    
+Pol   Name              Ext     Pin     Type     Used   Pterms  Level   
+--- --------            ---     ---     ----    ------  ------  -----   
+
+    A0                          6        V        -       -       -     
+    A1                          2        V        -       -       -     
+    A2                          3        V        -       -       -     
+    AYADDRWRITE                 0        I        1       -       -     
+    AYBC1                       17       V        2       14      1     
+    AYBDIR                      16       V        1       12      1     
+    AYDATAREAD                  0        I        1       -       -     
+    AYDATAWRITE                 0        I        1       -       -     
+    CLK                         1        V        -       -       -     
+    COMP                        7        V        -       -       -     
+    COUT                        22       V        -       -       -     
+    COUT                d       22       X        7       10      1     
+    COUT                ar      22       X        1       1       1     
+    COUT                sp      22       X        1       1       1     
+    D0                          14       V        1       8       1     
+    D0                  oe      14       X        1       1       1     
+    IOSELN                      4        V        -       -       -     
+    RDN                         5        V        -       -       -     
+    SNWEN                       15       V        1       10      1     
+    WRN                         8        V        -       -       -     
+    ar                          0        I        1       -       -     
+    sp                          0        I        1       -       -     
+    AYBC1               oe      17       D        1       1       0     
+    AYBDIR              oe      16       D        1       1       0     
+    COUT                oe      22       D        1       1       0     
+    SNWEN               oe      15       D        1       1       0     
+
+
+LEGEND    D : default variable         F : field      G : group
+          I : intermediate variable    N : node       M : extended node
+          U : undefined                V : variable   X : extended variable
+          T : function
+
+
+===============================================================================
+                                   Fuse Plot
+===============================================================================
+
+SP 
+ 05764 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+
+AR 
+ 00000 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+
+Pin #23  05808 Mode  xx 
+ 00044 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 00088 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 00132 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 00176 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 00220 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 00264 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 00308 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 00352 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 00396 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+Pin #22  05810 Mode  -x 
+ 00440 -------------------------------------------- 
+ 00484 -----x---x---x--x----x-------x--------x----- 
+ 00528 -------x----x------------------------------- 
+ 00572 -------x---------x-------------------------- 
+ 00616 -------x--------------------x--------------- 
+ 00660 -------x------------x----------------------- 
+ 00704 ----x--x------------------------------------ 
+ 00748 -------xx----------------------------------- 
+ 00792 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 00836 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 00880 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+Pin #21  05812 Mode  xx 
+ 00924 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 00968 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 01012 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 01056 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 01100 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 01144 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 01188 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 01232 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 01276 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 01320 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 01364 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 01408 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 01452 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+Pin #20  05814 Mode  xx 
+ 01496 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 01540 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 01584 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 01628 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 01672 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 01716 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 01760 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 01804 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 01848 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 01892 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 01936 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 01980 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 02024 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 02068 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 02112 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+Pin #19  05816 Mode  xx 
+ 02156 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 02200 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 02244 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 02288 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 02332 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 02376 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 02420 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 02464 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 02508 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 02552 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 02596 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 02640 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 02684 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 02728 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 02772 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 02816 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 02860 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+Pin #18  05818 Mode  xx 
+ 02904 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 02948 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 02992 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 03036 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 03080 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 03124 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 03168 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 03212 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 03256 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 03300 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 03344 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 03388 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 03432 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 03476 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 03520 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 03564 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 03608 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+Pin #17  05820 Mode  -- 
+ 03652 -------------------------------------------- 
+ 03696 ----x----x---x---x---x------x--------------- 
+ 03740 ----x----x---x--x---x--------x-------------- 
+ 03784 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 03828 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 03872 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 03916 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 03960 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 04004 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 04048 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 04092 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 04136 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 04180 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 04224 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 04268 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+Pin #16  05822 Mode  -- 
+ 04312 -------------------------------------------- 
+ 04356 ----x----x---x--x------------x-------------- 
+ 04400 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 04444 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 04488 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 04532 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 04576 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 04620 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 04664 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 04708 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 04752 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 04796 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 04840 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+Pin #15  05824 Mode  x- 
+ 04884 -------------------------------------------- 
+ 04928 -----x---x---x--x---x--------x-------------- 
+ 04972 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 05016 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 05060 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 05104 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 05148 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 05192 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 05236 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 05280 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 05324 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+Pin #14  05826 Mode  -- 
+ 05368 -----x---x---x---x---x------x--------------- 
+ 05412 ------------------------x------------------- 
+ 05456 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 05500 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 05544 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 05588 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 05632 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 05676 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+ 05720 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
+
+
+LEGEND    X : fuse not blown 
+          - : fuse blown 
+
+===============================================================================
+                                 Chip Diagram
+===============================================================================
+
+                               ______________
+                              |     acc      |
+                      CLK x---|1           24|---x Vcc                      
+                       A1 x---|2           23|---x                          
+                       A2 x---|3           22|---x COUT                     
+                   IOSELN x---|4           21|---x                          
+                      RDN x---|5           20|---x                          
+                       A0 x---|6           19|---x                          
+                     COMP x---|7           18|---x                          
+                      WRN x---|8           17|---x AYBC1                    
+                          x---|9           16|---x AYBDIR                   
+                          x---|10          15|---x SNWEN                    
+                          x---|11          14|---x D0                       
+                      GND x---|12          13|---x                          
+                              |______________|
+
diff --git a/hardware/audio_casette_card.lst b/hardware/audio_casette_card.lst
new file mode 100644
index 0000000..065a793
--- /dev/null
+++ b/hardware/audio_casette_card.lst
@@ -0,0 +1,74 @@
+LISTING FOR LOGIC DESCRIPTION FILE: audio_casette_card.pld           Page 1
+
+CUPL(WM): Universal Compiler for Programmable Logic
+Version 5.0a Serial# MW-10400000
+Copyright (c) 1983, 1998 Logical Devices, Inc.
+Created Sat Oct 17 12:42:37 2026
+
+  1:Name     acc;
+  2:PartNo   00;
+  3:Date     2026-10-11;
+  4:Revision 01;
+  5:Designer Joppe Blondel;
+  6:Company  unknown;
+  7:Assembly unknown;
+  8:Location unknown;
+  9:Device   g22v10;
+ 10:
+ 11:/* Constants */
+ 12:ar = 'b'0;
+ 13:sp = 'b'0;
+ 14:
+ 15:/* Pin assignments */
+ 16:/*   inputs */
+ 17:PIN 1 = CLK;
+ 18:PIN 2 = A1;
+ 19:PIN 3 = A2;
+ 20:PIN 4 = IOSELN;
+ 21:PIN 5 = RDN;
+ 22:PIN 6 = A0;
+ 23:PIN 7 = COMP;
+ 24:PIN 8 = WRN;
+ 25:/*   outputs */
+ 26:PIN 14 = D0;
+ 27:PIN 15 = SNWEN;
+ 28:PIN 16 = AYBDIR;
+ 29:PIN 17 = AYBC1;
+ 30:PIN 22 = COUT;
+ 31:
+ 32:/* Read reg0 */
+ 33:/*   places comparator output on D0 when reading addr0 */
+ 34:D0 = COMP;
+ 35:D0.OE = !IOSELN & !RDN & WRN & !A0 & !A1 & !A2;
+ 36:
+ 37:/* Write reg0 */
+ 38:/*   writes D0 to casette output port */
+ 39:/*   during a write COUT.D=D0 otherwise COUT.D = COUT */
+ 40:COUT.D = (!IOSELN & RDN & !WRN & !A0 & !A1 & !A2 & D0) #
+ 41:         ((IOSELN # !RDN # WRN # A0 # A1 # A2) & COUT);
+ 42:COUT.ar = ar;
+ 43:COUT.sp = sp;
+ 44:
+ 45:/* Write to SN76489 at addr 1 */
+ 46:SNWEN = !(!IOSELN & RDN & !WRN & A0 & !A1 & !A2);
+ 47:
+ 48:/* AY-3-8910 access at addr 2 (data) addr 3 (adress) */
+ 49:AYDATAREAD = !IOSELN & !RDN & WRN & !A0 & A1 & !A2;
+ 50:AYDATAWRITE = !IOSELN & RDN & !WRN & !A0 & A1 & !A2;
+ 51:AYADDRWRITE = !IOSELN & RDN & !WRN & A0 & A1 & !A2;
+ 52:AYBDIR = AYDATAWRITE # AYADDRWRITE;
+ 53:AYBC1 = AYDATAREAD # AYADDRWRITE;
+
+LISTING FOR LOGIC DESCRIPTION FILE: audio_casette_card.pld           Page 2
+
+CUPL(WM): Universal Compiler for Programmable Logic
+Version 5.0a Serial# MW-10400000
+Copyright (c) 1983, 1998 Logical Devices, Inc.
+Created Sat Oct 17 12:42:37 2026
+
+ 54:
+
+
+
+Jedec Fuse Checksum       (5c1a)
+Jedec Transmit Checksum   (46c6)
diff --git a/hardware/audio_casette_card.pld b/hardware/audio_casette_card.pld
new file mode 100644
index 0000000..9d05e00
--- /dev/null
+++ b/hardware/audio_casette_card.pld
@@ -0,0 +1,53 @@
+Name     acc;
+PartNo   00;
+Date     2026-10-11;
+Revision 01;
+Designer Joppe Blondel;
+Company  unknown;
+Assembly unknown;
+Location unknown;
+Device   g22v10;
+
+/* Constants */
+ar = 'b'0;
+sp = 'b'0;
+
+/* Pin assignments */
+/*   inputs */
+PIN 1 = CLK;
+PIN 2 = A1;
+PIN 3 = A2;
+PIN 4 = IOSELN;
+PIN 5 = RDN;
+PIN 6 = A0;
+PIN 7 = COMP;
+PIN 8 = WRN;
+/*   outputs */
+PIN 14 = D0;
+PIN 15 = SNWEN;
+PIN 16 = AYBDIR;
+PIN 17 = AYBC1;
+PIN 22 = COUT;
+
+/* Read reg0 */
+/*   places comparator output on D0 when reading addr0 */
+D0 = COMP;
+D0.OE = !IOSELN & !RDN & WRN & !A0 & !A1 & !A2;
+
+/* Write reg0 */
+/*   writes D0 to casette output port */
+/*   during a write COUT.D=D0 otherwise COUT.D = COUT */
+COUT.D = (!IOSELN & RDN & !WRN & !A0 & !A1 & !A2 & D0) #
+         ((IOSELN # !RDN # WRN # A0 # A1 # A2) & COUT);
+COUT.ar = ar;
+COUT.sp = sp;
+
+/* Write to SN76489 at addr 1 */
+SNWEN = !(!IOSELN & RDN & !WRN & A0 & !A1 & !A2);
+
+/* AY-3-8910 access at addr 2 (data) addr 3 (adress) */
+AYDATAREAD = !IOSELN & !RDN & WRN & !A0 & A1 & !A2;
+AYDATAWRITE = !IOSELN & RDN & !WRN & !A0 & A1 & !A2;
+AYADDRWRITE = !IOSELN & RDN & !WRN & A0 & A1 & !A2;
+AYBDIR = AYDATAWRITE # AYADDRWRITE;
+AYBC1 = AYDATAREAD # AYADDRWRITE;
\ No newline at end of file
diff --git a/hardware/audio_casette_card.sim b/hardware/audio_casette_card.sim
new file mode 100644
index 0000000..e212fce
--- /dev/null
+++ b/hardware/audio_casette_card.sim
@@ -0,0 +1,79 @@
+%SIGNAL
+PIN   6 =  A0 
+PIN   2 =  A1 
+PIN   3 =  A2 
+PIN  17 =  AYBC1 
+PIN  16 =  AYBDIR 
+PIN   1 =  CLK 
+PIN   7 =  COMP 
+PIN  22 =  COUT 
+PIN  14 =  D0 
+PIN   4 =  IOSELN 
+PIN   5 =  RDN 
+PIN  15 =  SNWEN 
+PIN   8 =  WRN 
+%END
+
+%FIELD
+%END
+
+%EQUATION
+AYADDRWRITE =>
+    A0 & A1 & !A2 & !IOSELN & RDN & !WRN
+
+AYBC1 =>
+    !A0 & A1 & !A2 & !IOSELN & !RDN & WRN
+  # A0 & A1 & !A2 & !IOSELN & RDN & !WRN
+
+AYBDIR =>
+    A1 & !A2 & !IOSELN & RDN & !WRN
+
+AYDATAREAD =>
+    !A0 & A1 & !A2 & !IOSELN & !RDN & WRN
+
+AYDATAWRITE =>
+    !A0 & A1 & !A2 & !IOSELN & RDN & !WRN
+
+COUT.d  =>
+    !A0 & !A1 & !A2 & D0 & !IOSELN & RDN & !WRN
+  # !COUT & IOSELN
+  # !COUT & !RDN
+  # !COUT & WRN
+  # A0 & !COUT
+  # A1 & !COUT
+  # A2 & !COUT
+
+COUT.ar  =>
+    0 
+
+COUT.sp  =>
+    0 
+
+D0 =>
+    COMP
+
+D0.oe  =>
+    !A0 & !A1 & !A2 & !IOSELN & !RDN & WRN
+
+SNWEN =>
+    A0 & !A1 & !A2 & !IOSELN & RDN & !WRN
+
+ar =>
+    0 
+
+sp =>
+    0 
+
+AYBC1.oe  =>
+    1 
+
+AYBDIR.oe  =>
+    1 
+
+COUT.oe  =>
+    1 
+
+SNWEN.oe  =>
+    1 
+
+%END
diff --git a/hardware/casette.jed b/hardware/casette.jed
deleted file mode 100644
index 4ae757a..0000000
--- a/hardware/casette.jed
+++ /dev/null
@@ -1,54 +0,0 @@
-
-CUPL(WM)        5.0a  Serial# MW-10400000
-Device          g22v10  Library DLIB-h-40-1
-Created         Sat Oct 03 16:22:02 2026
-Name            casette
-Partno          00
-Revision        01
-Date            2026-10-03
-Designer        joppe
-Company         unknown
-Assembly        None
-Location        unknown
-*QP24 
-*QF5892 
-*G1 
-*F0 
-*L00416 00000000000000000000000011111111
-*L00448 11111111111111111111111111111111
-*L00480 11111111101110111011011110111111
-*L00512 10111111110111111111111011110111
-*L00544 11111111111111111111111111111111
-*L00576 11101111111110111111111111111111
-*L00608 11111111111111101111111111111111
-*L00640 11110111111111111111111111100111
-*L00672 11111111111111111111111111111111
-*L00704 11110110111111111111111111111111
-*L00736 11111111111111111110111111111111
-*L00768 01111111111111111111111100000000
-*L00896 00000000000000000000000000001111
-*L00928 10111011101110111011111101111111
-*L00960 11111111000000000000000000000000
-*L01472 00000000000000000000000011111011
-*L01504 10111011101110111111011111111111
-*L01536 11110000000000000000000000000000
-*L02144 00000000000011111011101110111011
-*L02176 10111111011111111111111100000000
-*L02880 00000000000000000000000011111011
-*L02912 10111011101110111111011111111111
-*L02944 11110000000000000000000000000000
-*L03648 00001111101110111011101110111111
-*L03680 01111111111111110000000000000000
-*L04288 00000000000000000000000011111011
-*L04320 10111011101110111111011111111111
-*L04352 11110000000000000000000000000000
-*L04864 00000000000000000000111110111011
-*L04896 10111011101111110111111111111111
-*L05344 00000000000000000000000011111011
-*L05376 10111011101110111111011111111111
-*L05408 11111111111111111111111111110111
-*L05440 11111111111111110000000000000000
-*L05792 00000000000000000010111111111111
-*L05824 11110011000000110000000000000000
-*C5BE4
-*6A87
\ No newline at end of file
diff --git a/hardware/compile.sh b/hardware/compile.sh
new file mode 100755
index 0000000..625bea5
--- /dev/null
+++ b/hardware/compile.sh
@@ -0,0 +1,2 @@
+#!/bin/bash
+/opt/packages/wincupl/cupl -jaxfl g22v10 audio_casette_card.pld
\ No newline at end of file
diff --git a/memory.mk b/memory.mk
index 9a4dadd..50595cc 100644
--- a/memory.mk
+++ b/memory.mk
@@ -16,6 +16,9 @@ BIOS_ROM_SIZE           := 0x0780
 BASIC_ROM_START		:= 0x0800
 BASIC_ROM_SIZE		:= 0x2200
 
+SN76489_ROM_START	:= 0x2a00
+SN76489_ROM_SIZE	:= 0x1000
+
 BIOS_RAM_START		:= 0xc000
 BIOS_WP_RAM_START	:= 0xc800
 BASIC_RAM_START		:= 0xce00
diff --git a/scripts/encode.py b/scripts/encode.py
index 2bb4140..50230b7 100644
--- a/scripts/encode.py
+++ b/scripts/encode.py
@@ -106,11 +106,10 @@ class PulseWriter:
         self.bytes(struct.pack("<H", crc16(block_data)))
         self.byte(0x00) # Make sure the last byte has its last edge
 
-def header(pulses: PulseWriter, path:Path) -> None:
+def header(pulses: PulseWriter, path:Path, file_size: int) -> None:
     fname = path.name
-    fsize = os.path.getsize(path)
     data = (
-        struct.pack("<HH", math.ceil(fsize/BLOCK_SIZE), fsize)
+        struct.pack("<HH", math.ceil(file_size/BLOCK_SIZE), file_size)
         + fname.encode()[:32].ljust(32, b' ')
     )
     pulses.block(TYPE_BINARY, data)
@@ -126,6 +125,12 @@ def main() -> None:
     )
     parser.add_argument("input", type=Path, help="input file to encode")
     parser.add_argument("output", type=Path, help="output WAV file")
+    parser.add_argument(
+        "--max-size",
+        type=int,
+        metavar="BYTES",
+        help="encode at most this many bytes from the input file",
+    )
     parser.add_argument("--sample-rate", type=int, default=48_000)
     parser.add_argument(
         "--t-short",
@@ -152,6 +157,13 @@ def main() -> None:
         parser.error("--t-short must be less than --t-long")
     if not 0.0 <= args.amplitude <= 1.0:
         parser.error("--amplitude must be between 0 and 1")
+    if args.max_size is not None and args.max_size < 0:
+        parser.error("--max-size must not be negative")
+
+    input_size = os.path.getsize(args.input)
+    encoded_size = (
+        input_size if args.max_size is None else min(input_size, args.max_size)
+    )
 
     try:
         pulses = PulseWriter(
@@ -165,14 +177,14 @@ def main() -> None:
 
     # create header block
     pulses.space(5.0)
-    header(pulses, args.input)
+    header(pulses, args.input, encoded_size)
     pulses.space(1.0)
     with open(args.input, "rb") as f:
-        while True:
-            data = f.read(BLOCK_SIZE)
-            if not len(data):
-                break
+        remaining = encoded_size
+        while remaining:
+            data = f.read(min(BLOCK_SIZE, remaining))
             raw(pulses, data)
+            remaining -= len(data)
 
     pulses.space(1.0)
     with wave.open(str(args.output), "wb") as wav:
diff --git a/tapes/silver_surfer.wav b/tapes/silver_surfer.wav
new file mode 100644
index 0000000..c407dd5
Binary files /dev/null and b/tapes/silver_surfer.wav differ
diff --git a/tapes/sn76489.wav b/tapes/sn76489.wav
new file mode 100644
index 0000000..9767b23
Binary files /dev/null and b/tapes/sn76489.wav differ