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Subject: Re: Need advice wiring up a CPLD
Date: Thu, 3 Oct 2002 21:48:54 +0100
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"Christopher R. Carlen" wrote in message
> markp wrote:
> > "Christopher R. Carlen" wrote in message
> > news:3D9C5E6E.email@example.com...
> >>Oh, one other important thing! The CPLD runs at 3.3V, so I need level
> >>shifting anyway.
> >>Thanks for your interest.
> >>Good day!
> > If you're using buffers you might want to consider using 74LVC4245A
> > shifting buffers from Philips, that way you can drive from the PLD 3.3V
> > logic and be able to select 3.3V or 5V CMOS levels on your outputs.
> > http://www.philipslogic.com/products/lvc/pdf/74lvc4245a.pdf
> > Mark.
> Hmm, in this case there is zero likelyhood of having to output 3.3V
> What is the likelyhood that commercial instruments in the next few years
> will have user inputs that are 3.3V level instead of 5V TTL compatible
Pretty low I guess, they'd probably make them backwards compatible with bomb
proof inputs anyway.
> There are so many logic levels these days, it makes sense to keep the
> external world interface standardized on one thing, so all instruments
> can talk to each other. 5V works for me. I hope it stays that way.
OK, the reason I mentioned it is because it is easy to go from LVTTL to 5V
CMOS, and easy to go from LVTTL to 3.3V CMOS, but it's quite difficult to
have LVTTL inputs and to be able to select 3.3V or 5V CMOS outputs without
fitting different chips. Interest value only really.
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