VEP: EPROM programmer

[srowe]

I've just got a new cartridge which doesn't seem to have been documented yet. It's a basic EPROM programmer from the '80s

I've managed to dump the EPROM that contains the programming code, which I'll start to disassemble. I'll also create a schematic for it but if anyone has the original documentation I'd be very interested.

[beamrider]

Just wondered - how can it program an EPROM from the cartridge port - don't you need 18V or something to burn an eprom?

[srowe]

Judging by the text in the EPROM you need to attach an external 25v power supply

[Vic20-Ian]

Nice find.

Part of the Audio Computers set with VCR etc.?

[srowe]

Nice find.

Part of the Audio Computers set with VCR etc.?

Correct, but not included in the documentation you emailed me.

[Mike]

Some of the traces on the board look like they acted as fuses at some time.

It's also interesting to see yet another piece of software located in the I/Ox range ($9C00 as written on the EPROM label).

[srowe]

Some of the traces on the board look like they acted as fuses at some time.

There's some damage to the solder mask (and maybe the traces under), I think that's mechanical. The one trace looks to be a change from /CRW to /VRW, I also remember this on my VCR (from the same manufacturer).

It's also interesting to see yet another piece of software located in the I/Ox range ($9C00 as written on the EPROM label).

Indeed, I've not done a detailed dissassembly yet but it seems to use BRK as a compact way of jumping back to the main processing loop.

[Mike]

It's also interesting to see yet another piece of software located in the I/Ox range ($9C00 as written on the EPROM label).

Indeed, I've not done a detailed dissassembly yet but it seems to use BRK as a compact way of jumping back to the main processing loop.

You might check against Jim Butterfield's Tinymon, which they probably extended with a small routine to program the EPROM.

[srowe]

I've started to reverse-engineer the ROM, there seems to be 11 commands in total

https://eden.mose.org.uk/gitweb/?p=rom- ... rs-vep.asm

[Mike]

That's definitely different from Tinymon. As you say, BRK is (mis-)used as shortcut to form the main processing loop - they could have achieved the same result with RTS and a crafted return address on stack. Conversely, the BRK handler somewhat rudely purges the stack dump except the PC, which makes it unsuitable for debug purposes. Also, commands to access mass storage are missing. One would like to save and restore the EPROM dump from disk, no?

Which makes it a somewhat crude tool. One would fare better extracting the routines that do the actual job of accessing the EPROM and expand another monitor with those routines, as transient utility perhaps.