Re: Red Alert help needed (6502 CPU question too)

At 10:33 AM 5/3/2004, Rodger Boots wrote:
>Franklin Bowen wrote:
>
>>The crystal on my board is different, 11.7?, I think. I'll verify it later.
>>
>>You were right! I tied RDY high and the board displayed something ...
>>and then locked up! I'll see if I can make more progress tonight or
>>tomorrow. I have the RA coin switch tied to JAMMA coin 1 so I wonder if
>>RA needs the signal inverted. The only reason I can think of tying the
>>coin switch to RDY is if they were missing coin drops? Hmmmm ... maybe
>>not. The code to catch the coin signal would still need to execute and I
>>don't see how pausing the processor would help that.
>>
>>The /IRQ line driver baffled me. It's default is low and the only time
>>it goes high is if the game is running properly and /C070 gets
>>strobed! I still don't get that.
>
>
>/IRQ gets driven low at vertical sync. That triggers the interrupt to
>update all the video information. The interrupt routine would then do a
>read to C070 which resets /IRQ high and retrieves stored data from IC 8A
>(unused?).
>
>/IRQ would normally be high with low pulses if the program were running.
>
>I don't think your coin switch level was a problem, /NMI would have been
>low if the coin switch or service switch were activated.

The board locked up because I had pulled the /IRQ driver. Plugged it back
in and I am now the proud owner of a fully working Red Alert boardset, even
speech and cocktail mode works!

You're right about /IRQ and the coin switch.

My crystals are 11.73MHz main, 12.5MHz audio, and 6MHz (I think) speech.

Thanks for the help Rodger. I really appreciate it.

--
Franklin Bowen (Franklin@Bowen.net)
http://fmbbowen.com:39353  
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