PIAs are not too difficult to control, just remember the Control Lines (Direction) need to be set first, then you can read/write to the ports. It's the IRQ that is slightly tricky, the CA and CB ports in particular.

I want to do the same for the 6532...it has a timer. The RAM is easy to test ... but haven't taken the time to work out the timer section.

I've found that a thorough reading of the PIA info is very helpful, the 8255 has a sweat spot where you can write directly to the port with only one byte...on Game Plan MPUs this allows me to test the LED without having to go into a lot of work.

Still I am putting most of my development time into the cracking of the codes for the pod. Again, if anyone is interested in Disassembling the pods... I am attempting to take the 6802 pod code apart as it is the shortest, only 400 bytes. The ports are known and I figure if we know what the pod will accept then we know almost all the codes. The ERROR codes are my next project. I will force the unit to misread a RAM spot by writing to ROM and see what happens. More tonight, maybe...

John :-#)#

At 01:25 PM 07/03/2002 -0500, Kev wrote:

Has anyone written PIA scripts? Specifically I'm looking for 6821 stuff but
anything would be appreciated.

John has pointed out 6520 scripts & I've got data sheets in hand but I
thought I'd check 1 more time before I roll my own.

Thanks,
Kev