RE: 6522 vs 6526 (was Re: 6502 to 8501: new details)
Date: 2002-02-26 09:53:18

Hallo Nicolas,

> P0-P4 and P6-P7. P5 is not there!

OOPS. Didn't noticed that. 

> Right. But actually both chips are overkill, they have many more
> capabilities than just a single I/O port. A chip like the 6529
> would better suit the needs, but it has the big disadvantage of
> not having a data direction register.

The 6502->8501 design is based on my 6502->6510 design. And the 6510 has a
data-direction register. (Although I wonder if it is used ever again aftre
the first initialisation) AFAIK the 8501 has a DDR as well. So the 6529
won't do. Just try to design the I/O-port only using plain TTL-IC's. It is
possible but you need a lot of IC's. And THAT is the reason I choose for the
6522/6526: saving space and less soldering to do.

> I think both the 6526 and 6522 are good enough for testing
> the concept of the adaptor during prototyping.

Just curiousity: what do you have in mind to replace the port?
   / __|__
  / /  |_/     Groetjes, Ruud
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