EPROM suggestions

[msknight]

Hi Folks,

After asking on StarDot, I've got a TL866II Plus on the way and I've sorted out the software to program it via Linux.

I'm looking for EPROM suggestions to use please, as so far the only one I've found is this - https://cpc.farnell.com/atmel/at27c256r ... dp/SC09509 - which is a program once chip and apart from A14 being on pin 27 and something called VPP on pin 1, as long as the programmer will write to it (which I'm not sure of) then as pins 1 and 27 are tied high anyway, I can't see it making much of a difference.

But obviously I don't want to buy a few of these and find myself in trouble... so I thought I'd ask for recommendations first.

Michelle.

[Moggy]

A 32k PROM seems a bit overkill to me plus I think this would need some weird pin lifting to play ball.

For more modern devices let Mark or Lardo be your guide, for myself I'm an old fashioned dinosaur who gets by with ancient 2764 devices, 2 pin lifts
2 wires to solder and off we go. Yes they are old yes they may be unreliable all I can say is they have worked for me for many years and when you consider the first ZXpands ( issues 1 and 3 ) had them fitted from 2011 onwards they are a safe bet I think.

[Moggy]

Another thought that occurred to me is that some zeddies that are still working were factory fitted with old style EPROMS, so that means at least 43 years data retention once programmed, whether this would apply to re-flashing an old 2764 these days I can only guess.

[1024MAK]

Ooo Moggy, are you flashing again!

I'll get to modern EPROMs later (train about to arrive at the station I'm getting off at).

Burning (programming) an old EPROM should (assuming it's not been excessively worn from many reprogrammings) completely replace the charge on the memory cells. So it should be good for ten+ years again. But old chips may fail for other reasons.

Mark

[Moggy]

Ooo Moggy, are you flashing again!

I'll get to modern EPROMs later (train about to arrive at the station I'm getting off at).



Mark

Cheeky thing you shouldn't be looking ! A man's flashing is his own private affair!!

Serious head on I'll be interested to hear about what you think best for modern jobbys and if they are easier to program because as much as I like my old tat it takes a bit of fettling and I'm getting a bit too old to stuff mushrooms any more plus my stocks are dwindling.

[msknight]

I'm going to avert my delicate eyes and wait for Mark's wisdom on the matter!

[1024MAK]

I'm looking for EPROM suggestions to use please, as so far the only one I've found is this - https://cpc.farnell.com/atmel/at27c256r ... dp/SC09509 - which is a program once chip and apart from A14 being on pin 27 and something called VPP on pin 1, as long as the programmer will write to it (which I'm not sure of) then as pins 1 and 27 are tied high anyway, I can't see it making much of a difference.

Modern programmers are aware of the various 27 series EPROM versions (well, from the 8K byte type onwards), so no worries there. VPP is the pin where the programming supply voltage (for example, some common values are 12V/12.5V/21V) is connected.

Yes, 27256 or 27C256 types can be used. See my updated post here.

Yes, 32K bytes is a bit wasteful, but these OTP (One Time Programmable in the cheaper plastic package) are reasonably cheap. And being new, should be reliable. These are, as far as I am aware, the lowest capacity parallel type available new.

Mark

[msknight]

OK - so I'll go for those write once chips from Farnell.

The thing that's on my mind, having not really dealt with eproms before is that I'm concerned that if I get it wrong, then it's a few quid down the drain.

This is made worse by the following...
*) Using Linux instead of Windows software means I lose the automatic functions of the windows software... but hey.
*) Xgecu's web site is not responding for me, even if I tell my home firewall to allow my desktop full access to the internet, coupled with the very low capture rate on web archive recently and I have my doubts about the company - (fancy that, a chinese product getting cloned by other chinese companies and the original chinese company is having problems stopping the fakes! Who'd have thought it.)
*) Xgecu themselves warn that the TL866II is discontinued and that there are many clones/fakes on the market (I'm fairly sure the one I've bought is going to be a clone) ... but I note that minipro says that it's only got experimental support for the (cheaper) replacement, the T48.

So I know I'm up against it from the outset. Hence I thought that an eprom would be a better option because I could erase and re-attempt if I got it wrong... but the more I read, I guess I'd need a separate eraser unit, which would be more money on top of what I'm already risking in the learning process here.

... hence I'm being cautious and asking more questions than I probably otherwise would.

[1024MAK]

Buy multiple OTP EPROMs.

Unless you go for the cheap 'n' tacky erasers from China (which have very unprecise mechanical timers, leak UV around the gaps of the EPROM access and have dodgy wiring) finding good quality erasers is not easy, and they are not cheap. And with second hand units, you will not know how much, if any life is left in the UV tube.

The vast majority of TL866II are clones. And the original manufacture discontinued them some time ago.

Mark

[Paul]

There are w27c512 eeproms with EPROM pinout that I often recommend.
These can often be reprogrammed and about the waste:
It's the question of price per piece and not 8k against 64k.
If you only want to replace the original I advise to fill the 64k with 8 times the 8k. This way it doesn't matter at which level the additional address lines are. Connect them to 5V or 0V, whatever might be closer, just don't let them float.
You can of course reduce the memory waste by using more than one content.
On the zeddy I normally use standard Sinclair R3 and big bang in one eeprom to be able to switch between them with a switch or jumper.