Questions tagged [mos-6522]

Questions about the MOS 6522 VIA (Versatile Interface Adapter) chip, used in e.g. the Commodore PET and the BBC Micro home computers.

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18 votes
2 answers
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Comprehensive test suites for MOS 6520 PIA / 6522 VIA / 6526 CIA

Are there any automated test suites for MOS 6520, 6522 and 6526 chips? I am looking for test suites aimed at making sure datasheet-based independent reimplementations of the above chips (e.g. FPGAs or ...
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10 votes
1 answer
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Could the Commodore 64 have used the 6522 VIA instead of the 6526 CIA?

The VIC-20 used a 6522 VIA chip with a couple of 8-bit PIO ports, a couple of timers and a (buggy) shift register. (The bug in the shift register could be worked around with external hardware or in ...
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5 votes
1 answer
833 views

Why does the Vic-20 have two VIA chips?

The Vic-20 uses the 6522 VIA for peripheral I/O. However, it has two of them. I find this surprising, particularly considering minimizing cost was an important design goal. Is there a reason why it ...
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