Unknown TI logic series
ard at p850ug1.demon.co.uk
Sun Dec 19 12:55:09 CST 2010
> > Later 7400 series chips for specialized functions (e.g. verge of SSI
> > and MSI) had not-really-TTL-compliant inputs and outputs for
> > specialized daisy-chain or low-fanin-load purposes. Look at the BI/RBO
> > pin of a 7447 etc. (It's an input AND an output! Wow!) It's easy to
> > see how this could be applied to some of the "stock" standard logic
> > functions to greatly cut pin counts for a desktop calculator, and I
> > suspect that's what the unique numbers are for.
> That was quite an anomaly in the 7447, but off-hand it is the only IC I
> can think of that being done in.
I am pretty sure the 7446 (high voltage version of the 7447) and 7448
(active high outputs) do the same thing, but I guess you don't regard
those as different.
The epansion inputs on some And-Or-Invert gates (and thus the expanders
that drive thim) are not normal TTL signals. In fact IIRC from looking at
the shcemaitcs of said ICs, pulling them hard in one dirtection will burn
out a transistor.
I also noticed a current-sensing TTL chip in the data book (I was looking
for something else....). I'll look up the detials if you're interested.
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