Posted By
Csabo
on 2024-10-29
12:23:14
|  Re: Checking interrupt status
One small thing to add: waiting for a given vertical position (raster line) by checking $FF1D is very common, and there's a C64 equivalent of this as well. However, on Plus/4 we also have this for the horizontal position: $FF1E (which can be both read and written). This is often used for simple raster bars:
ldx #17 ; 18 colors
ldy #$A8 ; horizontal position check
loop06 lda colors,x ; get next color
loop05 cpy $FF1E ; wait for horizontal position
bcs loop05 ; keep waiting **
;
sta $FF19 ; change border and...
sta $FF15 ; background color
dex
bpl loop06 |
