Reflected Playfield Timing

[Mikes360]

Hi Guys,

 

I am having issues with a scrolling reflected playfield. I cannot get the timing quite right for the second PF2 update. I have tried to follow the timings covered in the below topic:

 

http://atariage.com/forums/topic/149228-a-simple-display-timing-diagram/?hl=%2Bmirrored+%2Bplayfield+%2Btiming&do=findComment&comment=1820187

 

To be honest I couldn't quite conclude if I needed the second PF2 update to complete at the start of cycle 48 or the end (i.e. cycle 49) either way its not quite right I have attached a binary showing the jump I get on this boundary.

 

If anyone has any recommendations I would be very grateful.

 

Demo.bin

[Omegamatrix]

I didn't really look too closely at your rom, but I took a quick peek at one random line and it looked okay.

 

 

The write has to finish at cycle 48, counting cycles like this:

    sta    WSYNC
;---------------------------------------
    sta    HMOVE                 ;3  @3
    lda    (SkaterGfx),Y         ;5  @8
    sta    GRP0                  ;3  @11
    lda    LeftPF1,Y             ;4  @15
    sta    PF1                   ;3  @18
    lda    LeftPF2,Y             ;4  @22
    sta    PF2                   ;3  @25
    nop                          ;2  @27
    nop                          ;2  @29
    nop                          ;2  @31
    nop                          ;2  @33
    nop                          ;2  @35
    nop                          ;2  @37
    nop                          ;2  @39
    nop                          ;2  @41
    lda    RightPF2,Y            ;4  @45
    sta    PF2                   ;3  @48  must be at 48 for reflected PF update
    lda    RightPF1,Y            ;4  @52
    sta    PF1                   ;3  @55
    dey                          ;2  @57

[Mikes360]

I wonder if its my scrolling logic being slightly incorrect, ill take a look tonight.