Anbody any clues as to how UMC UM6522 chips are suffixed, i.e. how is the frequency indicated?
I've some UM6522 and UM6522A, are they both 1MHz or what?

Also, are generic CMOS 65C22 interchangeable with NMOS types?
Do I only have to change the values of pull-ups or do I have to do something more sneaky?
I seem to be getting a few intermitent problems with interrupt responses when using all CMOS devices, but with NMOS everything works perfectly.
Dave

The 6522A's should be 2 Mhz.

I plugged 65C22's into a VIC-20, and everything works fine.

Interrupt problems: The 65C22 does *NOT* have open-collector IRQ outputs like the NMOS parts do. If you've got other interrupt sources tied with them, then that could be your problem.

Pete

I looked in the Western Design Center DATA book & their 65C22 doesn't have an open drain on the IRQ's , but I checked in the Rockwell DATA Book, and their 65C22 does have an open drain on the IRQ's. I've really only used the Rockwell parts. I'm not sure what the other manufacturers parts have.
Ted Melton

Thanks for your quick response, why didn't I think of checking that.
Cheers
Dave