forked from johanberntsson/ozmoo
/
zaddress.asm
115 lines (105 loc) · 1.63 KB
/
zaddress.asm
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.addr !byte 0,0,0
.next_byte_state !byte 0
set_z_address
stx .addr + 2
sta .addr + 1
lda #$0
sta .addr
rts
dec_z_address
pha
dec .addr + 2
lda .addr + 2
cmp #$ff
bne +
dec .addr + 1
lda .addr + 1
cmp #$ff
bne +
dec .addr
+ pla
rts
set_z_himem_address
stx .addr + 2
sta .addr + 1
sty .addr
rts
skip_bytes_z_address
; skip <a> bytes
clc
adc .addr + 2
sta .addr + 2
lda .addr + 1
adc #0
sta .addr + 1
lda .addr
adc #0
sta .addr
rts
!ifdef DEBUG {
print_z_address
jsr dollar
lda .addr + 1 ; low
jsr print_byte_as_hex
lda .addr + 2 ; high
jsr print_byte_as_hex
jmp newline
}
get_z_address
; input:
; output: a,x
; side effects:
; used registers: a,x
ldx .addr + 2 ; low
lda .addr + 1 ; high
rts
get_z_himem_address
ldx .addr + 2
lda .addr + 1
ldy .addr
rts
read_next_byte
; input:
; output: a
; side effects: .addr
; used registers: a,x,y
sty .next_byte_state
lda .addr
ldx .addr + 1
ldy .addr + 2
jsr read_byte_at_z_address
inc .addr + 2
bne +
inc .addr + 1
bne +
inc .addr
+ ldy .next_byte_state
rts
set_z_paddress
; convert a/x to paddr in .addr
; input: a,x
; output:
; side effects: .addr
; used registers: a,x
; example: $031b -> $00, $0c, $6c (Z5)
stx .addr + 2
sta .addr + 1
lda #$0
sta .addr
!ifdef Z4 {
ldx #2
}
!ifdef Z5 {
ldx #2
}
!ifdef Z8 {
ldx #3
}
- asl .addr+2
rol .addr+1
rol .addr
!ifndef Z3 {
dex
bne -
}
rts