Still working out the pinball program. Yes, 5 years and still going strong. when I revamped a bit, my self test died a horrible death and I couldnt find worth a damn. Did some wolf trapping last night and some tricks to find out my difference. This one has me scratching my head.

the problem is the VIA timer test on the 65C22. I originally wrote it in 6502 plain and on the revamp, I changed to take advantage of the STZ command to clear things out. THAT is causing me a new headache now.

Original working code:

ViaTimerTest4
SEI
LDA #$00
STA Via_ACR
STA Via_IER
STA Via_IFR
STA IrqMode
STA IrqSource
JSR FlashLEDOnce


and the new exploding code:

ViaTimerTest4
SEI
STZ Via_ACR
STZ Via_IER
STZ Via_IFR
STZ IrqMode
STZ IrqSource
JSR FlashLEDOnce


I am scratching my head o this one...

_________________
"My biggest dream in life? Building black plywood Habitrails"

Here are a few guesses:

o STZ generates a spurious read cycle either before or after the write cycle.
o STZ generates a spurious write cycle before the write of the zero value.

Toshi

STA abs and STZ abs share the same cycle-by-cycle sequence in WDC's instruction operation table, both taking four clocks: one for op-code fetch, one for ADL, one for ADH, and one for the data store, with no spurious reads or writes. I've never had any problem with STZ, so I expect there could be a problem in the assembly process. Picking through the output .hex code should tell you.

Thanks. I still have yet to put it back to LDA #$00 to test it out, but the rest of the routine is identical between old and new versions with the difference being the change to STZ. (had a nasty bug after during the init where I deleted an INX in a clean memory area loop, causing the bugger to freeze and stay there and I figured I had something stupid I did like that in there. Tons of fun)

And on that aside, someone asked me to repair one of those kind of pinballs last week. Brought it home, dead CPU. So it had to await this bugger being finished. (my fault for taking so long)...

_________________
"My biggest dream in life? Building black plywood Habitrails"

Another test: put the LDA #$00 back in, but leave the STZ instructions. It could also be the case that some subsequent code depends on A being zero, as cleared by the initialization routine.

I put the actual game init code right after that test finishes up. I think I have it cleared up, according to the Good Housekeeping Seal. will be trying it out....

_________________
"My biggest dream in life? Building black plywood Habitrails"