EPROM Programmer

A place to discuss the ZX80's and ZX81's younger brother - the Sinclair ZX Spectrum
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valentin
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EPROM Programmer

Post by valentin »

I have a very simple EEPROM Programmer witch which I programmed the 28C256 EEPROM for the Harlequin. I would like to replace that ROM with a 27128 or 27C128, but I cannot program it with the programmer I have.

I have two questions:

1) can a ZX Spectrum be used to program EPROMs?

2) I know about the TL866II, but is there any DIY, simple EPROM programmer?
Valentin
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1024MAK
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Re: EPROM Programmer

Post by 1024MAK »

valentin wrote: Fri Jan 28, 2022 11:02 pm 1) can a ZX Spectrum be used to program EPROMs?
Yes, with an appropriate interface/expansion card. However, as far as I know, no new ones are made, so you will have to wait for one to come up on a trading site. But they are not very common, so you may be waiting for some time…

Of course, it is possible to make your own. But you would also have to write the software to drive it as well…
valentin wrote: Fri Jan 28, 2022 11:02 pm 2) I know about the TL866II, but is there any DIY, simple EPROM programmer?
In the past, yes. They were typically connected to a PC parallel printer port. The original ‘Willem’ programmers (built or kit) are this type.
But as parallel printer ports disappeared off PCs, so have these programmers.

With any DIY design, you have to build a suitable PSU to produce the 21V or 13V or 12V programming voltage and do the switching of this between the programming voltage and +5V for reading of the EPROM.

All the address and data lines of the EPROM need to be driven. It’s not a trivial thing.

You should be able to get a TL866II Plus for around £50 (not including any adapters, most of which you would not need anyway).

Mark
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Moggy
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Re: EPROM Programmer

Post by Moggy »

I have an EPROM burner that I use on my Spectrum 48+ or 128 2A mainly for burning ZX81 EPROMS, it also works on the ZX81 but sadly I don't have the ZX81 software only the Spectrum code so yes it is possible though I'm not sure if it will do the EPROM you are interested in without checking the manual.


EDIT TO POST.

It will do the 27128 which is the 25/21 volt device not the 27c128 which I believe is 12volt.
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valentin
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Re: EPROM Programmer

Post by valentin »

Thanks for the feedback, Mark, Moggy.

@Moggy: the programmer doesn't look very complicated, do you have the schematic? Will you be happy to share the code?

Many years ago - more than I'd like to admit - I remember when "the guy" who sold me a ZX Spectrum clone (the Romanian HC 85) for which my parents paid 8,000 lei on the black market (approx. US$160 back then or US$400 in today's money), fixed an issue I had by erasing one of the white ceramic USSR EPROMs with bright UV light then reprogramming it using a board connected to his ZX Spectrum clone.

I would love to be able to program EPROMs using nothing else that retro-technology.

I am curentlyn browsing eBay for a casette player / recorder. Please don't :lol:
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1024MAK
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Re: EPROM Programmer

Post by 1024MAK »

A long time ago in a galaxy far, far away.... (okay, around 1984/5) I started work on a ZX Spectrum EPROM programmer card for a ZX Spectrum. It was based on an Intel i8255 PIA (although the actual chip may have been from another manufacturer). But this project never got very far… (I did buy the chips though).

Some extra 74LSxxx chips were needed for address (actually I/O) decoding and control. And some transistors were used for switching the VPP programming voltage. I can’t remember how the VPP supply was intended to be generated.

You need eight data lines and 14 (27128 EPROMs) or 15 (27256 EPROMs) address lines. Plus /CS, /OE and /WE control signals. The 8255 provides 24 I/O pins.

I think /CS may have just been grounded. A manual switch was used to enable/disable the VPP supply and inhibit writing (override control of /WE). DIP switches or links/jumper shunts will be needed to cope with the pins on the various EPROMs that have different functions. E.g. pins 1, 20, 26, and 27.

See the diagram here.

Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp

:!: Standby alert :!:
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Re: EPROM Programmer

Post by Moggy »

Sadly whilst I don't have the skills for schematics I'm more than happy to scan each side of the board at a decent res' and list the various values on the components.

I can also supply the boards user manual and code for spectrum 16 and 48k if that is of any use?

I also have a 2716 programmer for the zx81 1k machine which is a bit crude as it only step programs but can double up as a 2k ROM board.
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valentin
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Re: EPROM Programmer

Post by valentin »

Thanks again for your prompt replies.

Mark, that EPROM compatibility image is brilliant! It proves that one doesn't need Photoshop or Visio skills to create a very useful diagram.

Moggy, your offer is greatly appreciated. I wonder if the programmer you have is the one described here: A "very-scottish" EPROMMER for the ZX81. If you take a good picture of the back of the PCB, we could compare that with the schematic below published by ZX-TEAM here:

Image
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1024MAK
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Re: EPROM Programmer

Post by 1024MAK »

valentin wrote: Sat Jan 29, 2022 9:23 pm Mark, that EPROM compatibility image is brilliant! It proves that one doesn't need Photoshop or Visio skills to create a very useful diagram.
I can’t take the credit for that diagram. I just copied it like everybody else has…

The design of the ZX Spectrum EPROM programmer that I was working on long ago would have been based on a English (as in language, not country) electronics magazine article. Maybe intended for another Z80 based home computer. Sorry, too long ago for my memory to recall…

Back then, I was unaware of the internet, and would not have known about Sinclair computers being popular in Germany. Or indeed anywhere else in Europe.

Hence it is possible that the ZX-Team schematic you posted is based on something older. Clue in the title “very-scottish”! :lol:

Ooh, I should add that memory mapping interfaces was common on the ZX81/TS1000 because there were thought to be spare areas in there memory maps (but this is not quite as simple as that).

But on a 48K ZX Spectrum, there are no spare areas in the memory map. Hence all I/O devices should be mapped to a Z80 I/O port address.

Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp

:!: Standby alert :!:
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :!:
Looking forward to summer later in the year.
Moggy
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Re: EPROM Programmer

Post by Moggy »

Not the same one as mine which came from a company (like most ZX ephemera manufacturing"companies" it was just a house) not far from myself at the time called EPROM Services.

However here are the pictures if they are of any use. The red lead on the underside is only a bridge I had to put on as the track was borked where X marks the spot.
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side two.JPG
side one.JPG
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