Added tinybasic

boot.asm

@@ -2,6 +2,10 @@ STACK_TOP = 0xFFFF
 DELAY_LOOPS_PER_MS = 40
 MONITOR_BASE = 0xC000
 MONITOR_ROM_SOURCE = 0x0080
+TINYBASIC_BASE = 0xD000
+TINYBASIC_ROM_SOURCE = 0x1000
+
+        .include "tinybasic.inc"
 
         .globl _main
         .globl _delay_ms
@@ -10,6 +14,8 @@ MONITOR_ROM_SOURCE = 0x0080
         .globl _enable_interrupts
         .globl _disable_interrupts
         .globl _jump_to
+        .globl _monitor_uart_putc
+        .globl _monitor_uart_getc
         .globl monitor_image_end
         .globl s__DATA
         .globl l__DATA
@@ -29,6 +35,11 @@ boot_copy:
         ld de, #MONITOR_BASE
         ld bc, #(monitor_image_end - MONITOR_BASE)
         ldir
+
+        ld hl, #TINYBASIC_ROM_SOURCE
+        ld de, #TINYBASIC_BASE
+        ld bc, #TINYBASIC_SIZE
+        ldir
         jp init
 
 .area _ITABLE (ABS)
@@ -58,6 +69,13 @@ boot_copy:
         .dw ctc_isr          ; CTC channel 2: vector 0x44
         .dw uart_isr         ; CTC channel 3: vector 0x46
 
+; Stable entry points for programs living alongside the monitor.
+; C050: write the character in A. C053: return a character in A, or 0.
+.org MONITOR_BASE + 0x50
+        jp monitor_service_putc
+.org MONITOR_BASE + 0x53
+        jp monitor_service_getc
+
 .area _HOME
 init:
         di
@@ -110,6 +128,38 @@ monitor_image_end:
 
 .area _CODE
 
+; Monitor ABI services preserve all working registers. PUTC also preserves AF;
+; GETC returns the received byte (or zero) in A.
+monitor_service_putc:
+        push    af
+        push    bc
+        push    de
+        push    hl
+        push    ix
+        push    iy
+        call    _monitor_uart_putc
+        pop     iy
+        pop     ix
+        pop     hl
+        pop     de
+        pop     bc
+        pop     af
+        ret
+
+monitor_service_getc:
+        push    bc
+        push    de
+        push    hl
+        push    ix
+        push    iy
+        call    _monitor_uart_getc
+        pop     iy
+        pop     ix
+        pop     hl
+        pop     de
+        pop     bc
+        ret
+
 .macro MAKE_ISR entry, handler
         .globl handler
 entry: