Trevor Makes' Breadboard 28C-Series EEPROM Burner Is Powered by an Arduino Nano
Built using an Arduino Nano and two 74HC573 latches, this parallel programmer can write an 8kB C64 ROM chip in "a few seconds."
Computer engineer Trevor Makes has designed a low-cost programmer designed to make putting vintage computing ROM dumps onto real hardware easier, driven by an Arduino Nano and compatible with 28C-series parallel electrically erasable programmable read-only memory (EEPROM) chips.
"I have several projects I'm working on [which] require burning some custom ROM chips," Makes explains. "I decided to try out 28C-series EEPROMs, because even though they're more expensive than other PROMs they don't require higher voltage sources or UV light for erasing or programming — making them much easier to interface with. In fact they can be written over a plain computer bus just like an SRAM [Static RAM] chip, making them useful as a storage device as long as some particular timings are observed."
Makes had a look at previous designs for devices, which would allow 28C-series chips to be read and written on a modern PC — with period-appropriate hardware having typically relied on the long-retired parallel port — but found nothing to his liking, so set about building his own using an Arduino Nano microcontroller board.
"The biggest challenge with using an Arduino," Makes explains, "is the limited number of IO [Input/Output] pins for interfacing with a computer bus. An 8kB EEPROM, for example, requires eight data lines, 13 address lines, and a pair of read and write signals — 23 lines in total — while an Arduino Nano only has 20 IO pins, and that drops to 18 if you plan on using the serial connection with a computer."
Makes' solution was to use a pair of 74HC573 latches to expand the input/output capabilities of the Arduino Nano, providing a 64kB address space — enough for the vintage hardware Makes was targeting with the programmer. The resulting device fits on a single breadboard, with some impressively neat wiring, and allows the Arduino Nano to burn chips with Intel HEX files in "a few seconds" at a 115kbps connection speed.
The schematic and source code for the EEPROM burner are available on Makes' GitHub repository, under the permissive MIT license. More information is available on Makes' Reddit post.