Test Board

[Grant Stockly]

An 8bit AVR at 20MHz is too slow for a 2MHz 8080.

The AVR is fast enough, but it would require a CPLD.

I interfaced a SCENIX directly to the ISA bus once. It required external address decoding. I think I was running at either 1 or 8MHz bus speed, but with like 30 wait states, so I'm not sure what the "final" speed was.

The INSTANT the ISA would access the scenix, the scenix would ask for wait states. It was tough. The scenix was running at 50MHz. Probably not as efficient though.

A CPLD and an AVR is MORE than fast enough. Its not that the AVR wasn't fast enough to process the data, but that its not fast enough to read the address, figure out what goes where, return data, etc. Too much to think about in the 1us allowed.

[rgjones]

Originally Posted by Grant Stockly

A CPLD and an AVR is MORE than fast enough. Its not that the AVR wasn't fast enough to process the data, but that its not fast enough to read the address, figure out what goes where, return data, etc. Too much to think about in the 1us allowed.

Thats the conclusion Alex Freed came to when he used a 20MHz avr for his Psuedo disk project although I thought that at 60Mhz it might just be fast enough ....

I think I am going to hook my test board up to the Apple II bus anyway - a good excercise to get to know my Logic Analyzer

[Grant Stockly]

What Logic Analyzer do you have? The DigiView?

[rgjones]

Originally Posted by Grant Stockly

What Logic Analyzer do you have? The DigiView?

I bought the 34 CHANNEL LA1034 LOGICPORT LOGIC ANALYZER

http://www.pctestinstruments.com/

[Grant Stockly]

It looks a lot like the DigiView (software compression and signal interpretation).

I have the 18 channel version. A 34 channel version came out for $1500 later on. Yours looks very competitively priced.