Re: 6522 VIA inputs

Date: Fri, 21 Apr 2017 21:38:27 +0200
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> On 2017-04-21, at 19:12, Mike Naberezny <> wrote:
>> Take a look at the MOS datasheet for the 6522 (If you can't find it, I can mail it to you), it has schematics for the port drivers for port A and port B, they differ, but both ports have a permanent pullup in form of a MOS transistor for each bit.

Yeah - thanks. I had only the Rockwell's one at hand with a somewhat misleading caption but it shows more or less the same, except that it shows a resistor instead of transistor. A cursory glance, together with the caption made me initially believe it to be only the output part and a kind of a final output stage inverter. The MOS and Synertek documents seem to be more accurate, even if their captions also talk about output only. I even downloaded the half-gig heavy MOS blueprint scan of the 6522 and it agrees with the MOS datasheet.

> The MOS 6522 datasheet can be downloaded from here:
> The port drivers are on page 3 of the PDF.  The Rockwell and Synertek 6522 datasheets are also on

Got those, thanks.

SD! -

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Received on 2017-04-21 20:00:02

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