dos33fsprogs/graphics/hgr/fake_bios/65c02_detect.s

11 lines
237 B
ArmAsm

; relies on different behavior of decimal mode on 6502 vs 65c02
detect_65c02:
sed ; set decimal mode
clc ; clear carry for add
lda #$99 ; 99 decimal
adc #$01 ; +1 gives 00 and sets Z on 65C02
cld ; exit decimal mode
rts