RE: ECM Bench kelp needed

[thergen@svn.net]

On Thu, 13 Jan 2000, Marteney, Steven J. wrote:

> Although the input thresholds are different, since Bruce's circuit is only
> driving 1 or 2 inputs from any given output, the output of an HC part will
> EASILY swing between 0 and 5V.  One needs to look at the Voh vs. current on
> the HC part and compare Voh to the Vih (min) spec on a 2732 or LS or other
> digital part.  There won't be a problem.  If LS parts are available, use
> them.  If HC parts are the only available easily, they will be fine. 


> Always
> remember, for low current drive virtually every digital output in the world
> will swing to within 1% of the supply rails.
> Steve

I disagree based not only on the datasheets but on pratical experience as
well.

Tom




> 
> -----Original Message-----
> From: thergen@svn.net [mailto:thergen@svn.net]
> Sent: Thursday, January 13, 2000 10:49 AM
> To: gmecm@efi332.eng.ohio-state.edu
> Subject: Re: ECM Bench kelp needed
> 
> 
> Bruce,
> 
> Try:
> http://www.digikey.com/scripts/US/DKSUS.dll?Detail?Ref=100075&Row=46625
> which is a 74ls161 (digikey part search on 74ls161).
> 
> The 74S161 is in the Schottky TTL family - faster, uses more power, inputs
> require more current.  It would probably work.
> 
> The 74HC161 is in the High Speed CMOS family - wider power supply range,
> low power, *different input threshold than regular TTL*.  The inputs may
> not be driven reliably by TTL or certain eproms like a 2732 (check the Voh
> spec on the eprom output and the Vih spec on the 74HC161 input).
> 
> Don't use the HC part.
> 
> The HCT family is more compatible than HC with the various flavors of TTL.
> 
> Hope that helps,
> Tom
> 
> 
> On Thu, 13 Jan 2000, Bruce Plecan wrote:
> 
> > I have a wiring diagram for my DIS signal generator that uses two
> 74LS161s.
> > I have been every where locally and no one has them.   I have found some
> > similiar part nos. at Digi-Key,  those being a:
> > DM74S161-ND,   and a
> > MM74HC161N-MM
> > Can I use these?, one perferable to the other?, what's the difference in
> the
> > three.
> > Thanks
> > Grumpy
> > 
>