1
0
mirror of https://github.com/cc65/cc65.git synced 2024-10-31 04:04:49 +00:00
cc65/libsrc/cbm610/crtc.s

58 lines
599 B
ArmAsm
Raw Normal View History

;
; Ullrich von Bassewitz, 28.09.1998
;
; Write to the CRTC.
;
.export write_crtc, read_crtc
.importzp crtc
.include "cbm610.inc"
; Write a value to the CRTC. The index is in Y, the value in A
.proc write_crtc
sta sedt1
lda IndReg
pha
lda #$0F
sta IndReg
tya
ldy #$00
sei
sta (crtc),y
iny
lda sedt1
sta (crtc),y
cli
pla
sta IndReg
lda sedt1
rts
.endproc
.proc read_crtc
sty sedt1
lda IndReg
pha
lda #$0F
sta IndReg
lda sedt1
ldy #$00
sei
sta (crtc),y
iny
lda (crtc),y
cli
tay
pla
sta IndReg
tya
ldy sedt1
rts
.endproc