Can you look at this code snippet for me from an ongoing project?
I have the Playfield in reflect mode, and I'm not using PF0.
I want to make sure the PF2 swap occurs on the right machine cycle.
I'm just about ready to run the full version on emulation.
Here is the snippet.....
Draw_Screen:
lda DrawH
beq V0 ;branch if DrawH = 0
H0:
; [70] from previous
sta WSYNC ; [70] + 3
; [73]
; sleep for 2 cycles.
lda FieldH00 ;[00] + 3
sta PF1 ;[03] + 3
lda FieldH01 ;[06] + 3
sta PF2 ;[09] + 3
lda FieldH02 ;[12] + 3
; kill some time
pha ;[15] + 3
pla ;[18] + 4
pha ;[22] + 3
pla ;[25] + 4
pha ;[29] + 3
pla ;[32] + 4
pha ;[36] + 3
pla ;[39] + 4
lda FieldH02 ;[43] + 3
;[46]
sta PF2 ;[46] 46,47, *48* (swap on 3rd cycle of sta dp)
lda FieldH03 ;[49] + 3
sta PF1 ;[52] + 3
dec ScanLine ;[55] + 5
beq Exit0 ;[60] stop drawing!
dec DrawH ;+2 [62] + 5
bne H0 ;[67] + 3 {taken}
;+ 2 {not taken)
;[69]
;DrawV is non-zero here...
V0:
sta WSYNC ;[69] + 3
;[72]
;sleep for 3 cycles...
lda FieldV00 ;[00]
etc..................
-Andrew Schwerin
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