EPROM emulators

[Realtime]

I finally found time to build a SOFTY-1 EPROM programmer using Chris Oddy's replica PCB. It's turned out very nicely.

The reason I mention it here is that I wanted to demonstrate SOFTY being used as an EPROM emulator connected to an external processing card, in this case a National Semiconductor SC/MP Application Card - part of their Low Cost Development System. This card has a socket for a 512 Byte (E)PROM and 256 bytes SRAM on board.

I've made a short video showing code being entered on the SOFTY and then run by the application card. Although it's a trivial bit of code (toggling the SC/MP Flag 0) it does show what might have been possible back in the day, enhanced by the SOFTY tape interface for loading and storing programs up to 1KB.

[SiriusHardware]

I like the Next-Gen font on the video intro.

That little monitor you are using seems to like the output from the SOFTY-1 but I presume that Chris O transformed the modulator output, as was, into a composite video output at the redesign stage?

This is probably one of the few systems you could practically use the EPROM emulator feature of the SOFTY-1 on as most slightly more modern systems will have slots for larger EPROMs.

[Timbucus]

Great video thanks for sharing - the keypad looks great what switches did you use to allow the (I assume) cardboard overlay?

[Realtime]

The overlay is a laminated photo of the original keyboard (or one of the originals??) glued onto a 3D printed frame. On all my recent projects I've used these 12x12x4.3mm switches. Low contact bounce and a reliable supplier.

[ortek_service]

Yes, that keyboard overlay does look rather good and similar-looking to the original - I don't think we ever found what the strange round red/brown switches originally used were.

I presume the printed overlay does flex quite well and does provide some tactile-feedback similar to 'bubble' / dome switches that were always hard to recreate yourself
- I think 'Snaptron' ones are now stocked by distributors (Digi-key / Mouser?), rather than previously only being able to get some sample kits / buy large quantities direct from Snaptron. Although these do require a bare gold etc plated PCB pad layout to work with the snap-sprung domes and an adhesive cover-lay to keep the dome springs in the right place (Not sure if they did ones you could solder at an edge to fit surface-mount style.

[Qbertni]

Snaptron S series have a pair of SMD tabs on one side that can be soldered down, they don't seem to be available from digikey.

[ortek_service]

Thanks for info - I do now recall seeing ones that could be attached via soldering, rather than needing to be held in place with a cover-lay that would seem to be tricky to do without some specialist jigging.

Snaptron did send me a link back in July, that Digikey were now a distributor, with a Snaptron products page there at:
https://www.digikey.co.uk/en/supplie...mpaign=digikey
But it wasn't clear if they now supplied Snaptron's full range, without looking through them all.

Although, when I selected UK as the country on Digikey, I couldn't find Snaptron in the list of Manufacturers.
And when searching on 'Snaptron', it seems all the listed products are 'Marketplace' items (supplied via third parties), and not actually stocked by Digikey themselves (in the the UK at least?)
https://www.digikey.co.uk/en/product...ALgJwPYJAXQF8g

[ijl_Bitsa]

Dataman S4 EPROM programmer is able to emulate EPROMs also…
It has a ribbon cable connection on the back to a DIP header.
These still come up on eBay for sale occasionally.
Strangely, I seem to have 5 of these Dataman S4 programmers here ! How’d that happen, I don’t know !