There was a discussion about WSYNC before. Because i had (and have) no access to hardware where i
could test this, i had to believe that WSYNC needs 5 instead of the normal 3 clocks.
But my name is Thomas and i have to see before i believe anything.
So i slightly modifieded the code of the latest z26-release (v1.37). I changed the execution time for WSYNC to 5:
*** TIAWrite.asm: ***
H_WSYNC:
;just one added line of code:
add [RClock],2 ; WSYNC needs extra clocks! Does it???
cmp [RClock],CYCLESPERSCANLINE ; did WSYNC come after end of line?
ja SetSkip ; yes, skip a line (** check this **)
Then i tested the patched emu with many games (River Raid, Atlantis, Pole Position, Oystron, TPS...) and all of them now displayed wrong (especially the scores, see River Raid!)
I used the trace mode, and when i looked at the logged code, it showed, that sometimes WSYNC started exactly 3 cycles before the end of a scanline. So when i changed the emu code, it had to skip those lines.
I also tried 4 cycles and there where still some errors.
If i'm not completely wrong, this little experiment should show, that WSYNC only needs 3(!) clocks.
Did anybody try a well timed routine and tested WSYNC? Are you absolutely sure?? If yes, where
am i wrong?
Help me please!
Thomas Jentzsch | *** Every bit is sacred ! ***
tjentzsch at web dot de |
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