Topic: Crazy idea for a hack...  (Read 1600 times)

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Offline Elgen

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Crazy idea for a hack...
« on: April 08, 2011, 07:45:49 AM »
Okay I've always been accused of getting really crazy ideas, and now I want to hear your opinion on this one.

I got my Top2005+ EPROM Programmer yesterday. It works fine and I love it. BUT it 'only' programmes EPROMs that are 8bit wide on the databus.
I think it could be cool to be able to programme say a 27c1024 (as it's used for ie. the MVS-bios).

To do that I would:

1) Start by finding an 8bit IC covering the same address space as the 27c1024 that my programmer know of; that would be 27c512.
2) I then take the file I want to programme and cut it in half, by taking all the lower 8 bits of the 16 bit bites i one file and all the higher in another. It should be fairly easy to find a hex editor that can do that; alternatively I could just write a little piece of code for it };-D
3) I now make an adapter for the programmer:
  a) All address lines from the 27c512 just goes to the corresponding lines on the 27c1024.
  b) For the datalines I make a switch; in position 1 the upper 8 bits are held high and the lower is connected to the data pins of the 27c512, in position 2 the lower 8 bits are high and the upper connected to the data lines (for this I will need a bit of TTL logic, but it doesn't sound too complex I think).
4) I then first programme the lower 8 bits for whole the address space, then flip the switch and programme the upper 8 bits.

My question is this: Do you think that'll work?

It all matter of if it's possible to reprogramme an IC that have already been programmed before WITHOUT an erasing step.
My theory is, that by pulling the bits not being programmed up, they will stay untouched by the programming step, also in the 2nd iteration.

But what do you all think; I'm I way off or what? };-P
« Last Edit: April 08, 2011, 08:16:45 AM by Elgen »

Offline Phu

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Re: Crazy idea for a hack...
« Reply #1 on: April 08, 2011, 09:02:38 AM »
2 points:

1) You can hold the data pins high with pull-up resistors, no logic needed. But you might want a couple of 74LS244s as data buffers to be switch controlled.

2) It'll theoretically work, as long as the two chips use the same programming algorithm. The bigger EPROMs are known for there algorithm differences.

-- Richard
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Offline moggy

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Re: Crazy idea for a hack...
« Reply #2 on: April 08, 2011, 11:04:08 AM »
 Elgen, quote....4) I then first programme the lower 8 bits for whole the address space, then flip the switch and programme the upper 8 bits.


Hi Phu

I'm not too smart with these things but I think the burner I use on  my  48k spectrum achieves a similar thing with 27128 eproms.
Burn the first 8k flick a switch burn the second 8K.
have i got this right or am I totally thick!?

" I wear cotton but do not understand how it works "......E. Blackadder the third.

 :D :D :D :D