Hi, I’m trying to figure out how to talk to a LED sign I scrapped out of an arcade game. The display was made by Star Manufacturing, Inc. in 1991. The sign has 12 – 5x8 led panels. It uses a Rockwell R65C02P2 for the microprocessor and it has all the associated circuitry (SRAM, ROM, watchdog, 2 – 6821 PIAs and other various logic devices). The whole thing is powered off of 5v and the input came from a 10 pin header / ribbon cable that connected to the main game board.

The thing I’m having a hard time with is that only two of the pins on the 10 pin header go anywhere and they go to CA1 and CA2 on the first PIA chip. I checked the pins with a multimeter and CA1 was at 5vDC with a 7mvAC ripple, and CA2 was also at 5vDC with a 4mvAC ripple.

I was wondering if this sounded familiar to anybody, I’d like to find out what protocol it uses so I can hook it up to a microcontroller system.
Thanks!

I don't have a datasheet for the 6821 but the 6522's CB1 and CB2 pins are for parallel handshake OR serial shift register (clk and Data).

Your part might have shifted the data serially from the main board. Try to find a data sheet for the 6821. It will help greatly.

hope this helps...

Daryl

Thanks for the reply Daryl...

I found some info on the 6821 PIA chip here http://webpages.charter.net/coinopcauldron/piaarticle.html

Apparently those are the interrupt generating pins for port A.

I used 6821s before to interface with a 68HC11, but that was a while ago.

Can you get a dump of the EPROM from this display?

Reverse engineering that will probably tell you what you want to know.

Lee.

Found this ..

http://www.arcadehelp.com/manual/datasheets/6821.pdf

Lee.