Fooling around with EPROMs - share your stories!

Hi Gough!

I remember buying an EPROM programmer from a car boot sale for £0.50 ($1) it really was a 1970's heap of trash it must have been the lowest end model possible, the LED 7-segments dimmed when in operation, but it still worked! And for a few years I made some good pocket money remapping Ford RS Cosworth ECU's : ) I think a local mechanic still has it, I let him have it after I was done with it.

For erasing EPROMs, even the UK sunshine is ok for that Motorola provided loads of EPROM parts to speed up development of some other projects, so I'd label them all and cycle them in the sun : )

For yet another project, I was really stuck, I could only obtain the one-time programmable parts, which really were windowless EPROMs as I understand. No budget for the very hefty cost in-circuit emulators (think they cost a few $10k). Basically I had a few tubefuls of chances to get the code working : ) No pressure!

As an exercise in taking care, students should get given compilers with only a few dozen compile attempts : )

Oh, I like that idea ... "Warning: You have 1 attempt remaining. Make it good." OTP stuff is very much just a PDIP version, which, on the plus side means no accidental erasure. Sometimes you really need that pressure to make you think and plan your code appropriately ...

I was warned that while sunshine *can* work, different units can be less sensitive to the UV-A and UV-B in sunlight, and seeing the cells return 0xFF was not enough, as for reliability, someone seemed to suggest a figure of five times the amount of energy for the cells to just show all 1's. I'm not sure how true it is, but somewhere between 2-5x the just-erased time seems to be the recommended erase time.

I suppose you could easily do it with a few MOSFETs, external power supply and an Arduino nowadays, but taking the time to wire it up and understanding the programming cycle times is probably not worth it given the cost of a semi-decent programmer nowadays.

Good to hear your story .

- Gough

The company I worked for had a good little earner by reprogramming the EPROM's in the money machines (hole in the wall).

The bank would turn up with the masters, we'd copy them onto lots of others and charge them.

We also used EPROM's in the truckstops.

When I frst joined I noted they were cable tied in, and thought it strange.

Apparently because the boards were upside down, sometimes they'd fall out, and the cure (I was told it was from the manufacturer) was to use cable ties.

Needless to say I educated them on why they falling out and we swapped the sockets.

I've used an EPROM in a rudamentary controller I designed.

We mapped the output and setup a range of address'es that got stepped thru to produce a moving output.

We had 4 'pages' that were 4 higher bit address'es to effectively give 4 different pattern options.

I wrote a VB program to allow you to see the effect and it generated the hex file.

I think there are still some working around the town in the jackpot systems, along with some shooting stars in two casinos.

I have heard that sunlight will erase them but the ones we dealt with needed nearly 8 hours if I recall.

Mark

I vaguely remembered the wire-wrap style precision pin sockets versus the cheap pressed-metal wiper sort, and the proper pin sort was more expensive but really grabbed onto the legs. I suppose cable ties are better than nothing . Pulling chips out was always a bit of an operation ... an exercise in hoping you didn't flick the wrist at the last minute and cause a few bent pins.

Ah, nice stuff using it as a type of bit-mapped control. That's one of the reason I love the older parallel chips - they're basically asynchronous. Bang the address in, wait the requisite time, and the output magically appears. If minor glitches don't matter, or timing isn't critical, you don't really even have to latch the outputs anywhere. Of course, nowadays with the move to lower pin counts, the whole age of asynchronous parallel devices is also slowly coming to an end.

Thanks Mark for that memory .

- Gough

wire-wrap style precision pin sockets versus the cheap pressed-metal wiper sort, and the proper pin sort was more expensive but really grabbed onto the legs

Yep they were probably 10 times the price or more originally.

It's all very well using the cable tie, but they were so loose it was doubtful that some of the pins made adequate contact ... if at all.

It wasn't uncommon for them to not boot up after a power fail.

Strangely we never had an issue after they were changed.

Mark

They still are 10 times the price : ( but as far as I can see, if an IC is worth socketing then it is worth the

pin sockets.

It used to be possible to get pins on tape (like a flexible zero-height SIL header socket), you'd cut the tape

to the correct length and push it all in and solder. They were really handy, would be nice to locate some more.

I've never found them since though. I had to use the individual pins for the 3-digit LCD project.

I can vouch for the sensitivity to static charge on EProms.

Back in the late 1970's and early 1980's I had to be very careful around those devices.

For some reason, I generate a lot of charge when walking, especially on vinyl floors.

Some people claimed I could destroy an EPROM at ten feet, though I suspect they exaggerated.

I just made a habit of carrying the conductive foam for carrying the EPROMs and successfully took them to many locations and even overseas by air.

I even still have the UV lamp I used to erase them, though I am not sure I have a programmer.

In their day, EPROMs were a great way to update systems.

All I had to do was pop new EPROMS in and take the old ones back home for reuse.

It has taken a long time before I would trust these new fangled devices to store programs for updates.

Though I have found the SD Cards to be pretty reliable.

Your post brought back a lot of memories for me.

DAB

One thing to note is that you can some times save the day with "duff" EPROM contents by varying the supply voltage  slightly. Also if you have several of a given device then hopefully y ou can recreate a complete image from several broken ones stiched together( all a bit manual but doable!!)

The turned pin sockets were indeed pritty good and you can still get them although  you can get the 32/40 pin strips more easily these days.

I've seen the cable tie thing mostly in mobile applications were vibration must of been an issue. That said if you need to cut and replace the tie each time you reprogram it's not effective.

You will need to use re-usable ones in that instance!

EPROMs /Flash are still very useful for those Application in memory type applications more like the old computers but the SDCARD obviously wins hands down in most cases in terms of capacity and price etc now we load OSs and applications in to DRAM  before execution