RE: 6522 vs 6526 (was Re: 6502 to 8501: new details)
Date: 2002-02-28 08:56:25

Hallo allemaal,

> What about the 6532 that I have seen in the Commodore 
> printers? how do thethe pin-outs compare to 6522 or 6526 or 
> even the 8520 (Amiga CIA) or 8521(C128)? - do these match the 
> 6821?

This whole discussion started with why not using a 6522 instead of a 65226
as this would one invertor less (or was it the other way around?), Then the
6821 came in picture. Now the 6532 and others...

Don't forget one thing: the main reason I choose for the 6522 or 6526 is
that they have sepperate registers for DR and DDR just like the I/O-port of
the 6510, 8501 and 8502. The 6821 has NOT. So without changing the Kernal I
am not able to use the 6821 to replace the I/O-port. And even then, there is
a lot of software around manipulating the registers directly and thus will

INHO the 8520 can be used as well as the only difference is the structure of
some time-registers; registers that won't be used. As only one I/O-port is
used, even the 6530 and 6532 can be used.

So replacing a 6522, 6526 or 653x by a 6821 is impossible because of the
differences in the way the registers are arranged.

Theoretically the 6821 should be able to replace the 6520 but I'm not sure
about that. Having a lot of 6520's I once replaced a 6821 with a 6520 and
the device, a C64 IEEE-interface, didn't work anymore. OK, this does not
proove that a 6821 cannot replace a 6520 but still.... 
Remark: it just occured to me that the 6520 maybe only is
register-compatible and not timing compatible to the 6821. Being a 65xx-IC
it could be timing-compatible with the 6522 and we all know about the
problems connecting this 6522 to the C64.
   / __|__
  / /  |_/     Groetjes, Ruud
  \ \__|_\


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