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z80
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This commit is contained in:
Pedro de Oliveira 2014-08-14 05:55:30 +01:00
parent dc8797c576
commit 8d7e4dfcb0
1 changed files with 25 additions and 23 deletions
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48
zx-brainfuck/main.asm
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@ -61,38 +61,40 @@ end_main
; ------------------------------------- ; -------------------------------------
; opcode comes in A
loopup_table loopup_table
pop de pop de ; Remove return address from stack
ld de, lookup_tbl_opcodes ld de, lookup_tbl_opcodes ; Start of opcodes_tbl in DE
ld hl, lookup_tbl_routines ld hl, lookup_tbl_routines ; Start of routines_tbl in HL
ld c, $9 ld c, $9 ; Number of valid opcodes + 1
loopup_table_loop loopup_table_loop
ld b, a ld b, a ; B = A (opcode to run)
push bc push bc ; Push BC to the stack
ld a, (de) ; B = Opcode, C = counter
cp b ld a, (de) ; Read item from opcodes_tbl
jr z, lookup_table_found cp b ; Is it the same?
pop bc jr z, lookup_table_found ; Found it!
ld a, b pop bc ; Get values from stack
inc de ld a, b ; A = B (opcode to run)
inc de ; Next item in opcodes_tbl
inc hl inc hl
inc hl inc hl ; Next item in opcodes_routines
dec c dec c ; C = C -1
jr z, lookup_table_default jr z, lookup_table_default ; Is it 0? Non valid opcode
jr loopup_table_loop jr loopup_table_loop ; Repeat
lookup_table_found lookup_table_found
pop bc pop bc
jr lookup_table_ret jr lookup_table_ret
lookup_table_default lookup_table_default
ld de, continue ld de, continue ; DE = address to "continue" label
push de push de ; Send it to the stack
ret ret ; Return to last item in the stack
lookup_table_ret lookup_table_ret
ld e, (hl) ld e, (hl) ; Save the address of the routine to
inc hl inc hl ; be RETurned in DE
ld d, (hl) ld d, (hl)
push de push de ; Send it to the stack
ret ret ; Return to last item in the stack
; ------------------------------------- ; -------------------------------------