The ZX Spectrum Reverse Engineering and Clone Desgin Blog

Eprom Programmer

A site dedicated to the reverse engineering of the ZX Spectrum and related projects.

Eprom Programmer

Feb 4, 2007

As a refresher exercise (I've not done any digital design for ages) and because and EPROM programmer would be required to get the ZX Spectrum clone running, it seems a good idea to have a look at my old EPROM programmer design and implementation.

My original programmer was designed to run off the back of my ZX Spectrum as that was my only computer at the time, and I was mainly blowing new EPROMS to replace the one in the Spectrum.

I've not got the schematics for that programmer, but basically it used an intel 8255A Programmable Peripheral Interface chip to produce 24 I/O pins, enough for D0-7, A0-A13, OE and PRG line to the EPROM. This allowed 27C64 and 27C128 eproms to be blown.

Later, this same design was enhanced to allow the programmer to be used with a PC style parallel port. The design additions were an 8bit transparent latch and a parallel to serial shift register to serially shift the data out of the programmer through one of the parallel port status pins when in read mode. This would have worked with any PC style port and not require ECP or ECC modes, but would have been rather slow. The construction of this version was never completed, though it was 99% finished. Picture Here