Lee Fastenau wrote:
Almost... It works great in Z26, but the Supercharger hoses it
slightly. It
smells of newbie error... like the old missing "#" or someat.
Weird. I had to change an "unconditional" BEQ to a JMP.
That got me curious to take a look. :-)
I diffed ver 75 and 76 and found the change you mentioned.
dey
SLEEP 13
beq .enterHere (changed to jmp .enterHere in 76)
If you build reflex75.asm with -lreflex75.lst (generate a listing file)
then you can inspect what was generated for the SLEEP macro. (I've
removed some of the macro syntax for clarity)
12 f099 24 00 bit VSYNC
18 f09b ea nop
18 f09c ea nop
18 f09d ea nop
18 f09e ea nop
18 f09f ea nop
382 f0a0 f0 0d beq .enterHere
So what you have is the reliance on bit VSYNC setting the Z bit in the
flags. For a bit instruction, the Z flag is set as (Accumulator AND
VSYNC) so I think what you have proven is that 'in the wild' or at least
on a supercharger, reading VSYNC can return a non-zero value. You also
have a non-zero value in A. So the result must clear the Z flag. It does
seem to be a leap of faith to read from VSYNC, AND it with the
accumulator and hope to get a zero result in this situation.
If you really wanted to save a byte I think you could cook up something
in the 7 bytes that kills the 13 cycles and reliably sets the flags. For
instance you could remove the bit VSYNC and replace it with a LDA zpage
and then load from a known constant (or known non-zero) and do a bne...
- David
Anyway, new binary/source.
-Lee
PS: What's up with the "SPAM-LOW?!"
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