Back to the begin
This commit is contained in:
Joppe Blondel
+74
-538
@@ -4,581 +4,117 @@
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.org TAPE_LOADER_ROM_ADDRESS
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.org TAPE_LOADER_ROM_ADDRESS
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TAPE_PORT = 0x18
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TAPE_PORT = 0x18
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MAX_CYCLE_COUNT = 20
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MAX_BLOCK_SIZE = 0x100
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MAX_BLOCK_SIZE = 0x200
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STACK_TOP = 0xBFFF
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STACK_TOP = 0xBFFF
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WORK_BASE = 0xB000
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WORK_BASE = 0xB000
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OLD_SP = WORK_BASE + 0x00 ; word
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OLD_SP = WORK_BASE + 0x00 ; word
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OLD_IFF = WORK_BASE + 0x02 ; byte
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OLD_IFF = WORK_BASE + 0x02 ; byte
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SHORT_LEN = WORK_BASE + 0x03 ; byte
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LONG_LEN = WORK_BASE + 0x04 ; byte
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TRESHOLD = WORK_BASE + 0x05 ; byte
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SHORT_COUNT = WORK_BASE + 0x06 ; byte
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LONG_COUNT = WORK_BASE + 0x07 ; byte
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BLOCK_LENGTH = WORK_BASE + 0x08 ; word
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BLOCK_NUMBER = WORK_BASE + 0x0a ; byte
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NR_OF_BLOCKS = WORK_BASE + 0x0b ; word
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BLOCK_BUFFER = WORK_BASE + 0x100 ; MAX_BLOCK_SIZE
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BLOCK_BUFFER = WORK_BASE + 0x100 ; MAX_BLOCK_SIZE
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; #################################################3
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; #################################################3
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; Entry
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; Entry
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; #################################################3
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; #################################################3
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tape_loader:
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tape_loader:
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ld (OLD_SP),sp
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ld (OLD_SP),sp
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; Save interrupt state.
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; Save interrupt state.
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ld a,i
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ld a,i
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jp po,iff_was_off
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jp po,iff_was_off
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ld a,#1
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ld a,#1
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jr save_iff
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jr save_iff
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iff_was_off:
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iff_was_off:
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xor a
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xor a
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save_iff:
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save_iff:
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ld (OLD_IFF),a
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ld (OLD_IFF),a
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di
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di
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ld sp,#STACK_TOP
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ld sp,#STACK_TOP
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main:
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; Initial message.
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; Initial message.
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ld hl,#msg_start
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ld hl,#msg_start
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call print_with_irqs
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call print_string_ei
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; Read the first block
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call read_block
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jr z,1$
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ld hl,#msg_error_checksum
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ei
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call print_string
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call print_crlf
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di
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jp exit
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1$:
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; nr of blocks and filename stored in buffer
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ld hl,(BLOCK_BUFFER)
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ld (NR_OF_BLOCKS),hl
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; Print info of blocks
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ei
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ld hl,#msg_filename
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call print_string
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ld hl,#BLOCK_BUFFER
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inc hl
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inc hl
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call print_string
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call print_crlf
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ld hl,#msg_nr_of_blocks
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call print_string
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ld hl,(NR_OF_BLOCKS)
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call print_hex16
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call print_crlf
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call BIOS_FLUSH
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di
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; #################################################3
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; Read a consecutive list of blocks
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; #################################################3
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read_consecutive_blocks:
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ld bc,(NR_OF_BLOCKS)
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push bc
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1$:
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call read_block
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jr z,2$
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ei
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ld a,#'x'
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call BIOS_PUTC
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call BIOS_FLUSH
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di
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jr 3$
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2$:
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ei
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ld a,#'*'
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call BIOS_PUTC
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call BIOS_FLUSH
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di
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3$:
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pop bc
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dec bc
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push bc
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; Check for zero
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ld a,b
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or a,c
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jr nz,1$
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pop bc
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; All blocks are read
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ei
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ld a,#'V'
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call BIOS_PUTC
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call print_crlf
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call BIOS_FLUSH
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di
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; #################################################3
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; #################################################3
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; Exit
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; Exit
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; #################################################3
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; #################################################3
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exit:
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exit:
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di
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ei
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ld sp,(OLD_SP)
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call BIOS_FLUSH
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; Return code 0
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di
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ld a,#0
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ld sp,(OLD_SP)
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ld c,a
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; Return code 0
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; Restore caller's interrupt state.
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ld a,#0
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ld a,(OLD_IFF)
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ld c,a
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or a
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; Restore caller's interrupt state.
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ld a,c
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ld a,(OLD_IFF)
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jr z,return_di
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or a
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ei
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ld a,c
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ret
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jr z,return_di
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ei
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ret
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return_di:
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return_di:
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ret
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ret
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; #################################################3
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; Wait for next edge
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; D holds current comparator state
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; Returns B = loop count
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; #################################################3
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wait_edge:
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ld b,#0
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1$:
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inc b
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in a,(TAPE_PORT)
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cp a,d
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jr z,1$
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ld d,a
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ret
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; #################################################3
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; Wait for a full cycle
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; D holds the current comparator state
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; Returns B = loop count
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; #################################################3
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wait_cycle:
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ld b,#0
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1$:
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inc b
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in a,(TAPE_PORT)
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cp a,d
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jp z,1$
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ld d,a
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2$:
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inc b
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in a,(TAPE_PORT)
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cp a,d
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jp z,2$
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ld d,a
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ret
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; #################################################3
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; Eat A cycles
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; #################################################3
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eat_cycles:
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or a,a
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ret z
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ld c,a
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1$:
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call wait_cycle
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dec c
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jr nz,1$
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ret
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; #################################################3
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; Average 16 cycle intervals
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; Returns A = average loop count
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; preserves bc
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; #################################################3
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average16:
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push bc
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ld c,#16
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ld e,#0
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1$:
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call wait_cycle
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; Add loop count to e and take moving average
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ld a,e
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add a,b
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srl a
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ld e,a
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dec c
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jr nz,1$
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ld a,e
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pop bc
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ret
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; #################################################3
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; Calibrate
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; Gets short and long pulse lenghts and bit pulse counts
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; from training sequence
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; carry = succeeded
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; #################################################3
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calibrate:
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; establish comparator state
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in a,(TAPE_PORT)
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ld d,a
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; Wait for the first edge
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call wait_edge
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; Wait for the next edge to be back in phase with the
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; audio stream
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call wait_edge
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; Measure shoft pulses
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call average16
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ld (SHORT_LEN), a
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; Threshold for finding long pulse -> short*1.5
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; stored in c
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ld c,a
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srl a
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add a,c
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ld c,a
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; Wait for the first long pulse
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1$:
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call average16
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cp a,c
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jr c,1$
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; Measure long pulses
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call average16
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ld (LONG_LEN), a
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; Calculate period treshold
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ld b,a
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ld a,(SHORT_LEN)
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; Average between the two lengths
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add a,b
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srl a
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ld (TRESHOLD),a
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; Wait for first short for training
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ld c,a
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3$:
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call wait_cycle
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ld a,b
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cp a,c
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jr nc,3$
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; Count short cycles
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ld e,#1
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4$:
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call wait_cycle
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ld a,b
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cp a,c
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jr nc,5$
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inc e
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ld a,#MAX_CYCLE_COUNT
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cp a,e
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jp c,error_cycle_count
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jr 4$
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5$:
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ld a,e
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ld (SHORT_COUNT),a
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; Count long cycles
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ld e,#1
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6$:
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call wait_cycle
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ld a,b
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cp a,c
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jr c,7$
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inc e
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ld a,#MAX_CYCLE_COUNT
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cp a,e
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jp c,error_cycle_count
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jr 6$
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7$:
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ld a,e
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ld (LONG_COUNT),a
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; First cycle of short was already consymed
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ld a,(SHORT_COUNT)
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dec a
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call eat_cycles
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; Consume rest of training bits
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; 6 L/S pairs then last L
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ld h,#6
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8$:
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ld a,(LONG_COUNT)
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call eat_cycles
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ld a,(SHORT_COUNT)
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call eat_cycles
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dec h
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jr nz,8$
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ld a,(LONG_COUNT)
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call eat_cycles
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; Test calibration with sync byte
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call check_sync_byte
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ret
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error_cycle_count:
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ei
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ld hl,#msg_error_cycle_count
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call print_string
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call print_crlf
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di
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jp exit
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||||||
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||||||
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; #################################################3
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; Read one bit
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||||||
; carry = value
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; #################################################3
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read_bit:
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call wait_cycle
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ld a,(TRESHOLD)
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ld c,a
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ld a,b
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cp a,c
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jr c,2$
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; zero bit
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1$:
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ld a,(LONG_COUNT)
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dec a
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call eat_cycles
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or a,a ; clear carry
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ret
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||||||
; one bit
|
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||||||
2$:
|
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||||||
ld a,(SHORT_COUNT)
|
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dec a
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call eat_cycles
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scf ; set carry
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||||||
ret
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||||||
|
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||||||
; #################################################3
|
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||||||
; Read byte
|
|
||||||
; A = byte
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||||||
; #################################################3
|
|
||||||
read_byte:
|
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ld e,#0
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||||||
ld h,#8
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|
||||||
1$:
|
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||||||
call read_bit
|
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||||||
rl e
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||||||
dec h
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||||||
jr nz,1$
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ld a,e
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||||||
ret
|
|
||||||
|
|
||||||
; #################################################3
|
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||||||
; Check sync byte
|
|
||||||
; carry = succeeded
|
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||||||
; #################################################3
|
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||||||
check_sync_byte:
|
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||||||
call read_byte
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||||||
ld e,a
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||||||
ld a,#0xf0
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||||||
cp a,e
|
|
||||||
jr z,1$
|
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||||||
or a,a
|
|
||||||
ret
|
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||||||
1$:
|
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||||||
scf
|
|
||||||
ret
|
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||||||
|
|
||||||
error_wrong_sync_byte:
|
|
||||||
ei
|
|
||||||
ld hl,#msg_error_sync_not_found
|
|
||||||
call print_string
|
|
||||||
call print_crlf
|
|
||||||
di
|
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||||||
jp exit
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|
||||||
|
|
||||||
; #################################################3
|
|
||||||
; Read a block
|
|
||||||
; checksum in a
|
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||||||
; #################################################3
|
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||||||
read_block:
|
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||||||
call calibrate
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||||||
jp nc,error_wrong_sync_byte
|
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||||||
|
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||||||
; Get block number
|
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||||||
call read_byte
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||||||
ld (BLOCK_NUMBER),a
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||||||
|
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||||||
; Get block length
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||||||
call read_byte
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||||||
ld b,a
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||||||
push bc
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||||||
call read_byte
|
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||||||
pop bc
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||||||
ld c,a
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||||||
ld (BLOCK_LENGTH),bc
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||||||
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||||||
; Check block length against max length
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||||||
;ld hl,#MAX_BLOCK_SIZE
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||||||
;and a,a
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||||||
;sbc hl, bc
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||||||
;jp c,error_block_too_big
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||||||
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||||||
exx
|
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||||||
|
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||||||
ld bc,(BLOCK_LENGTH)
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||||||
ld hl,#BLOCK_BUFFER
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||||||
|
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||||||
1$:
|
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||||||
exx
|
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||||||
call read_byte
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||||||
exx
|
|
||||||
|
|
||||||
ld (hl),a
|
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||||||
inc hl
|
|
||||||
|
|
||||||
dec bc
|
|
||||||
; Check for zero
|
|
||||||
ld a,b
|
|
||||||
or a,c
|
|
||||||
jr nz,1$
|
|
||||||
|
|
||||||
; Read checksum
|
|
||||||
exx
|
|
||||||
call read_byte
|
|
||||||
|
|
||||||
; Calculate checksum of block
|
|
||||||
ld hl,#BLOCK_BUFFER
|
|
||||||
ld bc,(BLOCK_LENGTH)
|
|
||||||
push af
|
|
||||||
xor a,a
|
|
||||||
ld e,a
|
|
||||||
2$:
|
|
||||||
ld a,e
|
|
||||||
add a,(hl)
|
|
||||||
ld e,a
|
|
||||||
inc hl
|
|
||||||
dec bc
|
|
||||||
; Check for zero
|
|
||||||
ld a,b
|
|
||||||
or a,c
|
|
||||||
jr nz,2$
|
|
||||||
|
|
||||||
pop af
|
|
||||||
; e is calculated checksum
|
|
||||||
; a is received checksum
|
|
||||||
ld h,a
|
|
||||||
ld l,e
|
|
||||||
cp a,e
|
|
||||||
ret
|
|
||||||
|
|
||||||
error_block_too_big:
|
|
||||||
ei
|
|
||||||
ld hl,#msg_error_block_too_big
|
|
||||||
call print_string
|
|
||||||
call print_crlf
|
|
||||||
di
|
|
||||||
jp exit
|
|
||||||
|
|
||||||
|
|
||||||
; #################################################3
|
; #################################################3
|
||||||
; IO Helper functions
|
; IO Helper functions
|
||||||
; #################################################3
|
; #################################################3
|
||||||
print_with_irqs:
|
print_string_ei:
|
||||||
ei
|
ei
|
||||||
call print_string
|
call print_string
|
||||||
call BIOS_FLUSH
|
call BIOS_FLUSH
|
||||||
di
|
di
|
||||||
ret
|
ret
|
||||||
|
|
||||||
print_string:
|
print_string:
|
||||||
ld a,(hl)
|
ld a,(hl)
|
||||||
or a
|
or a
|
||||||
ret z
|
ret z
|
||||||
call BIOS_PUTC
|
call BIOS_PUTC
|
||||||
inc hl
|
inc hl
|
||||||
jr print_string
|
jr print_string
|
||||||
|
|
||||||
print_crlf:
|
print_crlf:
|
||||||
ld a,#13
|
ld a,#13
|
||||||
call BIOS_PUTC
|
call BIOS_PUTC
|
||||||
ld a,#10
|
ld a,#10
|
||||||
jp BIOS_PUTC
|
jp BIOS_PUTC
|
||||||
|
|
||||||
print_hex16:
|
print_hex16:
|
||||||
push hl
|
push hl
|
||||||
ld a,h
|
ld a,h
|
||||||
call print_hex8
|
call print_hex8
|
||||||
pop hl
|
pop hl
|
||||||
ld a,l
|
ld a,l
|
||||||
call print_hex8
|
call print_hex8
|
||||||
ret
|
ret
|
||||||
|
|
||||||
print_hex8:
|
print_hex8:
|
||||||
push af
|
push af
|
||||||
rrca
|
rrca
|
||||||
rrca
|
rrca
|
||||||
rrca
|
rrca
|
||||||
rrca
|
rrca
|
||||||
and #0x0F
|
and #0x0F
|
||||||
call print_hex_nibble
|
call print_hex_nibble
|
||||||
pop af
|
pop af
|
||||||
and #0x0F
|
and #0x0F
|
||||||
|
|
||||||
; fall through
|
; fall through
|
||||||
print_hex_nibble:
|
print_hex_nibble:
|
||||||
cp #10
|
cp #10
|
||||||
jr c,print_hex_digit
|
jr c,print_hex_digit
|
||||||
add a,#('A' - 10)
|
add a,#('A' - 10)
|
||||||
jp BIOS_PUTC
|
jp BIOS_PUTC
|
||||||
|
|
||||||
print_hex_digit:
|
print_hex_digit:
|
||||||
add a,#'0'
|
add a,#'0'
|
||||||
jp BIOS_PUTC
|
jp BIOS_PUTC
|
||||||
|
|
||||||
; #################################################3
|
; #################################################3
|
||||||
; Strings
|
; Strings
|
||||||
; #################################################3
|
; #################################################3
|
||||||
msg_start:
|
msg_start:
|
||||||
.ascii "TAPE DECODE TEST - PLAY TAPE"
|
.ascii "TAPE DECODE TEST - PLAY TAPE"
|
||||||
.db 13,10,0
|
.db 13,10,0
|
||||||
|
|
||||||
msg_short_len:
|
|
||||||
.ascii "Short len: "
|
|
||||||
.db 0
|
|
||||||
|
|
||||||
msg_long_len:
|
|
||||||
.ascii "Long len: "
|
|
||||||
.db 0
|
|
||||||
|
|
||||||
msg_treshold:
|
|
||||||
.ascii "Treshold: "
|
|
||||||
.db 0
|
|
||||||
|
|
||||||
msg_short_count:
|
|
||||||
.ascii "Short count: "
|
|
||||||
.db 0
|
|
||||||
|
|
||||||
msg_long_count:
|
|
||||||
.ascii "Long count: "
|
|
||||||
.db 0
|
|
||||||
|
|
||||||
msg_error_cycle_count:
|
|
||||||
.ascii "Cycle count out of bounds"
|
|
||||||
.db 0
|
|
||||||
|
|
||||||
msg_error_sync_not_found:
|
|
||||||
.ascii "Sync not found"
|
|
||||||
.db 0
|
|
||||||
|
|
||||||
msg_error_checksum:
|
|
||||||
.ascii "Checksum error"
|
|
||||||
.db 0
|
|
||||||
|
|
||||||
msg_filename:
|
|
||||||
.ascii "Filename: "
|
|
||||||
.db 0
|
|
||||||
|
|
||||||
msg_nr_of_blocks:
|
|
||||||
.ascii "Blocks: "
|
|
||||||
.db 0
|
|
||||||
|
|
||||||
msg_error_block_too_big:
|
|
||||||
.ascii "Block too big"
|
|
||||||
.db 0
|
|
||||||
|
|
||||||
|
|||||||
Reference in New Issue
Block a user