[retrotecchie]

Thanks for the extra info - very informative. I think I used the blank locations in a (copy of) my original ROM while I was originally developing code. My finished application for the board I have (with an EPROM containing the final code) didn't use the keypad or the display but instead read lookup tables from the top two ROM sockets which were fitted with ribbon headers and wired to a pair of D25 plugs. Into these plugs the user connected two EEPROM modules, external to the housing which contained information used to control a pair of 35mm Kodak slide projectors for use in a target shooting range.

User input was a set of switches (start, stop, pause, auto and manual plus a couple of others) allowing a sequence of slide numbers and timings to be automated as part of a multimedia training system.

I also used the board with the original keypad and a 2x16 LCD module in the companion 'programmer' for the system.

Happy days....the Territorial Army bought a dozen of these systems back in the early 90s. The unit I have was a factory 'spare' with the original production code.

Being the sad type I was back then, all my Z80 development was done on an ancient Spectrum +128 fitted with an internal cassette drive and a Centronics interface that allowed me to take hard copy of my code. I think I still have the +128 somewhere but the cassettes and all the hard-copy of my original development is long gone.

Thirty years, or so, on from the original project, I just think that revisiting my old Z80 stuff will happily keep me entertained when there isn't much on the telly.

Thanks for the help - I really do appreciate it.

Cheers

Mike