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mikew8760 · 5th Apr 2020, 11:47 am

Short (?) update on my adventures down the rabbit-hole!

Regarding what I thought were 'dodgy' EPROMS turned out to be a bit of a red herring. Having taken the trouble to look at old data sheets, I find that programming requires a Vpp in many cases of 25 volts and a pulse width of 45 - 55 ms. My all-singing, all-dancing programmer is deficient in this aspect. It only provides a highest Vpp of 21v (actually measured at 20.6) and a pulse of 1000us (1ms) max. I'm surprised and disappointed, as I would expect the designers of the programmer to have taken these requirements into account; perhaps more modern chips will program at these levels?

I found that it was actually possible to program my EPROMs by repeatedly hitting the 'program' button. It would fail at the first attempt at address 0, then 1, then 2 etc. Clearly the low Vpp and very short timing would not allow sufficient charge to be acquired by the floating gate.

But I'm still having problems with the old Paratronics NICE; it seems old age has produced some intermittent connections. So I have been forced to get out the big guns and try my old Microtek MICE II emulator!!

5th Apr 2020, 11:47 am	#11
mikew8760 Triode Join Date: Mar 2020 Location: Bristol, UK. Posts: 18	Re: Maplin Z80 SBC Short (?) update on my adventures down the rabbit-hole! Regarding what I thought were 'dodgy' EPROMS turned out to be a bit of a red herring. Having taken the trouble to look at old data sheets, I find that programming requires a Vpp in many cases of 25 volts and a pulse width of 45 - 55 ms. My all-singing, all-dancing programmer is deficient in this aspect. It only provides a highest Vpp of 21v (actually measured at 20.6) and a pulse of 1000us (1ms) max. I'm surprised and disappointed, as I would expect the designers of the programmer to have taken these requirements into account; perhaps more modern chips will program at these levels? I found that it was actually possible to program my EPROMs by repeatedly hitting the 'program' button. It would fail at the first attempt at address 0, then 1, then 2 etc. Clearly the low Vpp and very short timing would not allow sufficient charge to be acquired by the floating gate. But I'm still having problems with the old Paratronics NICE; it seems old age has produced some intermittent connections. So I have been forced to get out the big guns and try my old Microtek MICE II emulator!!