CIA In TTL?

[commatari]

Hello,

I've been curious as to replicating the various blocks of the 8520/or 6526 CIA chip in hardware using TTL ICs. Basically, how Commodore/MOS would have done it back in the day (mid 70s-early 80s).

The timers, counters, and interrupt circuits I'm especially interested in and wonder if you could add them on to a 6522 VIA of the period.


Any input would be greatly appreciated!

[psxphill]

It should be possible, but I don't believe mos actually did that when designing them. Having a chip fab on site has it's advantages.
 
 When building the 8520 embedded in the akaio for the CD32 they used an FPGA.