cbmeeks accidentally spoke the name of the IEEE-488 card, which got me thinking.
IEEE-488 is a communications standard also known as GPIB. (General Purpose Instruments Bus.)
It was commonly used to connect electronics test and laboratory equipment. Commodore PET used it as a peripheral bus.
TI made a lot of GPIB gear, especially the one-chip TMS9914A controller. They designed a GPIB card for the TI-99/4A, but it was not marketed.
The schematic for the TI-99/4A IEEE-488 card is here: http://www.mainbyte....tic/ieee488.jpg
It contains a DSR. It contains a PAL, however its used for only 4 output signals which are pretty obvious.
Here is the TI manual for the TMS9914A controller chip: http://bitsavers.tra...anual_Dec82.pdf
The first product of National Instruments was a GPIB card for the PDP-11. (Not to be confused with TI.. NI made an employee T-shirt saying "National Instruments--Not Selling Calculators since 1976.") NI had a second source or clone chip, NAT9914, pin compatible with TMS9914A controller.
I have a pile of GPIB bus testers in my garage with NAT9914 chips. I'm not sure if I have any actually useful GPIB devices. You can still get TMS9914A from China surplus.
Here is a Dr Dobbs article on making a GPIB: http://www.drdobbs.c...-gpib/184408548
I'm not saying I actually want a GPIB card, just collecting together the puzzle pieces here.
Edited by FarmerPotato, Fri Feb 8, 2019 5:02 PM.