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mikew8760 · 9th Mar 2020, 6:14 pm

Hi.

Yes, the behaviour of the EPROM's has me puzzled, but I have yet to try a few tests to pin down the nature of the 'fault'. I had thought it might the address decoding, but the LS devices all check out OK. As I mentioned before, I put a 6116 in the EPROM socket with the WR line connected to the '139 output and that all worked fine.

My EPROMS are all quite old, perhaps over 40 years old, but are OK on the programmer; the only thing that makes me suspicious is the Vpp voltage. I don't have any manufacturer's info on the 2716's, and some are of unknown origin, so not sure about the correct Vpp to use. I actually have some that will not program at all and some that I have used 21.5 volts to persuade them to accept code. They then read OK on the programmer, but not on the SBC. I have wondered if the Nicolet NICE may be at fault, but everything else works, although the so-called manual I downloaded from somewhere is quite poor; e.g. it has a command EPP, Enable Print Point, but nowhere describes how or what it is?

Thanks for the offer of EPROMS, but if and when I get a couple of flash devices that should be more convenient.

9th Mar 2020, 6:14 pm	#10
mikew8760 Triode Join Date: Mar 2020 Location: Bristol, UK. Posts: 18	Re: Maplin Z80 SBC Hi. Yes, the behaviour of the EPROM's has me puzzled, but I have yet to try a few tests to pin down the nature of the 'fault'. I had thought it might the address decoding, but the LS devices all check out OK. As I mentioned before, I put a 6116 in the EPROM socket with the WR line connected to the '139 output and that all worked fine. My EPROMS are all quite old, perhaps over 40 years old, but are OK on the programmer; the only thing that makes me suspicious is the Vpp voltage. I don't have any manufacturer's info on the 2716's, and some are of unknown origin, so not sure about the correct Vpp to use. I actually have some that will not program at all and some that I have used 21.5 volts to persuade them to accept code. They then read OK on the programmer, but not on the SBC. I have wondered if the Nicolet NICE may be at fault, but everything else works, although the so-called manual I downloaded from somewhere is quite poor; e.g. it has a command EPP, Enable Print Point, but nowhere describes how or what it is? Thanks for the offer of EPROMS, but if and when I get a couple of flash devices that should be more convenient.