On Sun, 18 Apr 2021, Karl Jacobs wrote:
Date: Sun, 18 Apr 2021 19:02:47 +0200
From: Karl Jacobs <[email protected]>
Reply-To: "Enhanced Machine Controller (EMC)"
<[email protected]>
To: "Enhanced Machine Controller (EMC)" <[email protected]>
Subject: [Emc-users] 7i92 hardware question
Hi all,
sorry if this has been asked before: I am planning on using a Mesa 7i92M
board and connect it to an existing BOB that has 10kOhm pullup resistors
to 5V on its 74ACT14 inputs. I know about the 3.3V logic and the 5V
input option of the Mesa boards, but I could not find definite info
about the outputs. They seem to have an open drain mode, but can they
safely take the 5V pullups or do I have to get rid of them (or connect
them to 3.3V)?
Thanks,
Karl
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Pullups to 5V are fine when the 7I92 I/O is in 5V tolerance mode.
(in fact the 7I92s built in 4.7K pullups are connected to 5V in
5V tolerance mode)
The outputs will swing to 5V even in push-pull mode (but are only actively
driven up to 3.3V, above that the pullups take over)
Peter Wallace
Mesa Electronics
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