This Web page last updated dated Dec 1 2010
In July I got an inquiry from someone in the UK who wanted to remake or back up his PROMs, so I asked Jeff about his PROM reader/writer. In late July 2010 I discussed PROM programming with Jeff Shook. Jeff used a homemade PROM reader/programmer, to make sense of his Digital Systems floppy controller, which was microprogrammed with PROMs to run the simple routines to read and write sectors. John Torode had to build a microprogrammed floppy controller, because in the early 1970's there weren't any microprocessors that could do the job. Jeff bought one of Torode's controllers. Later on, Dwight Elvey got one, figured out the microcode structure, and disassembled the code.
Jeff talks about his Digital Systems floppy controller on this Web page; Dwight Elvey discusses the microcode on this Web page. If you look at the microcontroller card schematic, the PROMs are the 3601's, which are versions of 82S23's.
- Herb Johnson
"I actually built the programmer for another project some time before I became interested in how the FDC-II controller worked [in 1980]. There isn't much documentation of my PROM programmer. Just a schematic diagram and two pictures of the top and the bottom. The photo of the underside of the bipolar PROM programmer shows it modified for reading only. The yellow wire near the 39 ohm resistor has been removed to ensure that no program power could be applied."
"I think the circuit design may have come from a magazine I found on the internet some time ago a very poor scan of a hand drawn schematic by Keith Wilson for a similar programmer. I have tried to enhance it and now it is mostly readable. I have attached the schematic for my programmer and the pictures. I will write up some operating instructions later. It would not be difficult to automate the operation using one of the USB to three 8 bit i/o port adapters I see on the internet." - Jeff Shook
Here are some PROM data sheets and PROM cross reference lists from various PROM manufacturers. This content is very hard to find today. - Herb Johnson
Here's a Phillips 82S123 data sheet
a JPEG of a Signetics cross-reference
and a larger cross-reference
a Signetics 82S23 data sheet with programming info
here's a National Semiconductor 82S188/288 data sheet with programming and cross-reference
AMD 27LS08 data sheet and programming
Radio-Electronics Feb 1981 has some kind of PROM programmer project.
Copyright © 2010 Herb Johnson