[sdiy] 93-series TTL logic

[Robin Whittle]

The 1978 Fairchild TTL (Transistor Transistor Logic) Data Book has a
section on 93xx devices.  There were standard, L low power and S
Schottky (Schottky low-threshold diode between collector and base to
stop the transistor saturating, so it could turn off faster) versions of
many chips.

I think the 9300 series was already going out of fashion in 1978.

Page 2-9 shows output circuits differing between 74xx and 93xx - with
the latter having an 80 ohm resistor in the positive drive circuit,
compared to 130 ohms for standard TTL.

The only chip in this series I have used is a 9368.  This has a 4 bit
latch and a 7 segment decoder, to drive a common-cathode 7 segment LED
display.  It has constant current output drivers, but I typically used a
270 ohm in series with each output pin as well, since the later LED
displays, such as those from Stanley, didn't need so much current.

The great thing about the 9368 is that it did the full hexadecimal
range, while others only did 0 to 9.

The 93xx range had some pretty fancy functions, including for arithmetic
logic and dual-port memory - clearly designed for making CPUs.

  - Robin             http://www.firstpr.com.au/rwi/dfish/