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cc65/libsrc/cx16/get_tv.s

32 lines
776 B
ArmAsm

;
; 2019-09-20, Greg King
;
; unsigned char get_tv (void);
; /* Return the video mode the machine is using. */
;
.export _get_tv
.include "cx16.inc"
.proc _get_tv
php
sei ; Don't let interrupts interfere
; Point to the video output register.
stz VERA::CTRL ; Use port 0
lda #<VERA::COMPOSER::VIDEO
ldx #>VERA::COMPOSER::VIDEO
ldy #^VERA::COMPOSER::VIDEO
sta VERA::ADDR
stx VERA::ADDR+1
sty VERA::ADDR+2
lda VERA::DATA0
plp ; Re-enable interrupts
and #$07 ; Get the type of output signal
rts
.endproc