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cc65/libsrc/nes/get_tv.s

38 lines
837 B
ArmAsm

;
; Stefan Haubenthal, 2007-01-21
;
; unsigned char get_tv (void);
; /* Return the video mode the machine is using */
;
.include "nes.inc"
.include "get_tv.inc"
.importzp tmp1, tmp2
;--------------------------------------------------------------------------
; _get_tv
.proc _get_tv
lda #TV::NTSC ; assume NTSC
tax ; clear
sta tmp1
sta tmp2
ldy tickcount
wait: cpy tickcount
beq wait
iny ; next tick
loop: cpy tickcount
bne over
inc tmp1
bne loop
inc tmp2
bne loop
over: ldy tmp2
cpy #9
bcc nopal
lda #TV::PAL ; choose PAL
nopal: rts
.endproc