patroclus

I want to build an eprom programmer, specialy for 27Cxxx.
Willem's one seems too dificult, as I have some experience in electronics but not much. I found these

http://home.quicknet.com.au/andrewm/eprom1/

It seems cool, but I can't understand the schematic.. when many lines merge into one, which one is which??
then I found this

http://www.zws.com/products/epromr2/index.html

Seems the easiest, and suposse to have same capabilities if not more. But.. maybe it is wrost?? What do you recommend me??
Thanks!

Exo

On the first scematic the bus lines are not numbered, this usually means the wires are just connected 1 to 1, so the upper wire wich goes into the bus is the upper one wich comes out again.

panic mode

It's called bus and the presentation is intended to save space on the diagrams. For example signals D0-D7 of ZIF1 socket connect to O0-O7 of the U6 and 1A-4B of the U7. This means you should connect D0, O0 and 1A, next line is D1, O1, 1B, third one is D2, O2, 2A etc.
These eight connection are one 8-bit data bus (thats what D0-D7 is).
You also have 14-bit address bus connecting outputs of chips U4, U4A, U5 and U5A (top to bottom) to address lines of the ZIF socket. If you count the outputs, you will see that there are indeed 14 of them and they are wired in same sequence to the Address bus A0-A13.
Anyway, if this is too complicated, don't bother. Try to do project you know you can handle and then try to progress step by step. This design is actually relatively simple but it's not meant for rookies. You might be better off by purchasing ready made programmer such as B+K. It will save you time and frustration.

Johnson777717

it looks like the person who drew the schematic didn't want to draw all of the traces going to their corresponding pins. If the person who drew the schematic were to do that, the drawing would become a maze of traces, and figuring out each trace would become a nightmare. You'd have crossing traces, and it would become difficult to figure the schematic out. The traces feeding into one line simply means that the traces are to be applied to their proper pins, but the drawing was simplified in this manner, so that you could see the other traces from more discrete components. To find out where each trace is connected, you may have to look at the PCB layout picture, and follow the traces there.

I don't know anything about EPROM so I couldn't tell you if this is a good set or not.

patroclus

I see, after spending some time with PCB schematic, I understud.
It's not that hard now, but it would be my firts copper PCB project, as I only worked with wiring on universal boards yet. Is it maybe too much to start with? Is it challenging? maybe it is a good start point??

Johnson777717

Well it will definately be a challenge, for a starting point. I suggest starting with a very basic circuit and making a PCB for that. That way, you'll allow yourself to learn the basics before diving into a dense PCB for the EPROM programmer. Plus, with a basic circuit, if you mess up, you're not out all of the time and money that you;ll spend making the EPROM PCB. What you learn from the simple circuit can be applied to the dense EPROM circuit. Then again, it is possible to start off with the EPROM programmer.

patroclus

Yes, I'm with you, I'll first do some test circuit.
Anyway, you think manual line drawing would do the job for the programmer? or I'll need some other method or technique?

patroclus

by the way, I don't know if someone could explain me something.. if you see

http://home.quicknet.com.au/andrewm/eprom1/

PCB, instead of schematic, the counters 74HC393, that suppose to address the PROM, don't seem to be conected to address inputs in order. I mean, from less significant bit, it connects to A0, A3, A10, A11, ...
Isn't it supose to be A0, A1, A2, A3, .. so when increasing counter, we move onto next memory position?? this really is driving me crazy... thanks guys.

nettron1000

Pat, i doubt it really matters in which order the memory is addressed as long as you know where to find it later. Its connected that way just to make the layout alittle easier.
Like as already bin suggested it prolly would be better for you to try something abit simpler. Actually you can still build a Static ram programmer, just build a simpler version of one to learn how they work.
Heres a link to one of my own designs, its very similar to what you are inquiring about, although its alot simpler.

http://www.geocities.com/nettron1000/2816SRAM.html

__________________
Two roads diverged into a woods...i took the one less travelled by. R. Frost.

patroclus

Yes, seems cool. Indded, the circuit is very similar to an EPROM programmer.
Thanks

Anyway, I've been thinking about it and.. wouldn't it be better to use EEPROM like 29F040 rather than 27Cxxx EVPROMs?? I mean, the firsts ones can be erased easily and so.. I'm not much into this so if any of you can give me any clue I'd be very grateful. Making a programmer for any of this is also very similar project, that the meaning of this question.

Thanks again for you help

Nigel Goodwin

I think the main question here is 'what are you wanting to build an EPROM programmer for?'. If it's to program an EPROM for a specific device or application, using a FLASH memory chip might not be suitable - it's something you would need to check carefully.

patroclus

First, I need to replace some damaged 27c128. they are from a spectrum computer. I have the bin files, and wanted to program a new 27c128. But, is it possible to replace it with 29Fxxx EEPROM??

I mean, is it possible to replace any 27Cxxx with 29Fxxx for only-read purposes??

patroclus

No one knows if it's possible to replace any 27Cxxx with 29Fxxx for only-read purposes?? As 29Fxxx usually have same or lower acces time, there should be no problem, am I wrong?