HP board id?

J. David Bryan jdbryan at acm.org
Thu May 14 21:52:00 CDT 2015

On Thursday, May 14, 2015 at 14:21, Marc Verdiell wrote:

> Thanks a million!

You're welcome.

> As for the receivers, it can go into straight TTL apparently, I read
> that somewhere in an HP manual.

Both TTL and LSTTL (but not STTL or HTTL) will work with an appropriate 
pulldown resistor.  LSTTL is recommended for the lower power and improved 
speed over TTL.  The pulldowns are necessary to guarantee logic zeros when 
driven by the original CTuL or newer 75121 parts, which have open-emitter 

Section 5-7, "Computer Backplane Assembly Requirements," of the 
aforementioned interfacing manual details the recommended circuits.

                                      -- Dave

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