6522 VIA inputs

From: silverdr_at_wfmh.org.pl
Date: Fri, 21 Apr 2017 11:21:05 +0200
Message-Id: <EF039A7C-4801-4D58-80CE-EBCE5A15E6CA@wfmh.org.pl>
In 1541 bits five and six of the VIA port at $1800 are used to initialise the device id. In the older drives, both respective pins are grounded via bridged trace fields. In the newer there is a DIP switch block. I saw this schematic uncountable number of times, yet only recently it struck me that when the trace bridges are cut the pins are left floating (!). There are no pullups whatsoever. Now the question - is this a documented feature of the VIA that can be safely relied upon? Something like "unconnected pins will always read 1 when configured as inputs". I had a look at the 6522 datasheet and found only "Port B lines represent one standard TTL load in the input mode [...]"

SD! - http://e4aws.silverdr.com/

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Received on 2017-04-21 10:00:05

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