Re: OT - TTL Circuit: Pullup vs Supply

On Wed, 06 Sep 2006 18:10:18 -0600, you wrote:

>can anyone explain what any pro's or con's there might be on tying
>static input pins on a TTL device 'high' through a pull-up resistor vs
>straight to the +5V supply? Im working on laying out a ASIC replacement
>PCB and I had the board designed with pull-up resistors but tracing them
>is becoming a PITA so I thought about just tying them to the +5V rail as
>an alternative.

        I could swear I recall reading something in the "applications notes"
section of one of my old TTL books about a pull-up (or pull-down) resistor
providing improved noise immunity, which might be important for control
pins (such as reset* / preset* pins on flip-flops or shift registers) whose
function isn't needed in the application in question...

        ...but I'll be damned if I can *find* the book in question! The books
I have handy don't say anything about this... so I've either lost/misplaced
the book that did, or I'm completely misremembering having ever read it in
the first place. :)
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solarfox@DON'TMESSWITHtexas.net (Gary Akins jr.)
http://lonestar.texas.net/~solarfox
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Received on Wed Sep 6 22:35:27 2006