Funny TTL pinouts (was Deck of IBM PLAYING CARDS) - test-drb@ccmp.vtda.org

18 Dec 2005

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Subject: Funny TTL pinouts (was Deck of IBM PLAYING CARDS)
   From: shoppa_classiccmp at trailing-edge.com (Tim Shoppa)
   Date: Sun, 18 Dec 2005 10:06:47 -0500
     To: cctalk at classiccmp.org

"Chuck Guzis" <cclist at sydex.com> wrote:
  On 12/17/2005 at 10:37 PM woodelf wrote:
 I  downloaded some motorola application notes from
bitsavers.
Wow they sure had a  lot of  different types of  TTL. I wonder how only 
the 74xx became the only TTL used today? 
 I think the short answer is "second sources"--you had at least 4 big
 players, TI, National, Moto and Fairchild all producing 7400-series logic.
 Some of the earlier TTL (Moto 400/500-series) had mid-line (pins 4 and10)
 power supplies, which turned out to be not as convienient for PCB layout.
 And, although it's largely forgotten, 7400 TTL shares a fair number of
 pinouts with the older DTL circuits.

 By the time LSTTL was out, everyone had pretty much standardized on the
 74xx line. 
Don't forget, some of the "standard" 74xx line are actually National or
Fairchild or Motorola parts that were not originally given
74xx numbers (because they weren't TI parts) but they were eventually
second-sourced by TI and given 74xx numbers. "Imitation is the
truest form of flattery."

The ones that come to my mind most immediately are the Fairchild
9310 and 9316, later known as 74160 and 74161, all massively used
synchronous counters.  I also seem to recall part numbers like 40160
as Motorola tried to back-incorporate them into their TTL lineup. (Am
I confused as usual?)

I think the funny Vcc/Gnd pinouts (often 4 and 10) were actually thought
to be good for some reason in some specialized PCB designs - I think
I see these show up on some early MSI quad latches (7475) and counters
(7490, actually pins 5 and 10). I don't know if these were cross-incoprorated
from parts that started out at Motorola or Fairchild or National or what. 

The mid chip Vcc and ground went all the way back to the Moto and Fairchild
RTL (in dip) or opposing pins in the 8/10/12 leaded TO5 (can) varient.

However when it came to part numbers Moto is infamous for a plethora of 
"house numbers" where the number is not EIA or ISO or anthing else and 
was special for a project or customer.  Most of the other vendors did 
that as well but Motorola was wild.  HeathKit was a common consumer of
house numberd parts from many vendors.

Allison