28C040 Flash ROM from old AT boards.

[Ian Field]

A while ago I sorted through the tea chest full of old PC boards and found
numerous boards had flash ROM onboard. Before scrapping the tattier
examples, I harvested any flash ROMs there were.

Unfortunately (so I am told) these ROMs can't just be written to like a
standard static RAM - also unfortunately, I've been unable to find any
schematics/programming info on how to program these ROMs.

Please does anyone have a schematic for a (preferably minimalist) flash ROM
programmer?

Thanks.

[Raymond Wiker]

The 28C040 appears to be an EEPROM, which is slightly different from a
Flash ROM. It can be programmed fairly easily; for a simple circuit for
a smaller EEPROM chip, see http://sbc.rictor.org/28256.html .

[Raymond Wiker]

See also http://www.brielcomputers.com/phpBB2/viewtopic.php?t=56 .

[Ian Field]

"Raymond Wiker" <rwi...@gmail.com> wrote in message
news:m24nfyc...@unknown-00-1d-4f-f8-0e-e3.lan...

Thanks.

Any other resources you can think of?

[Theo Markettos]

Ian Field <gangprob...@ntlworld.com> wrote:
> Please does anyone have a schematic for a (preferably minimalist) flash ROM
> programmer?

Some early EEPROM and flash were dual-voltage (5V operation and 12V program), but
otherwise the schematic is just the same as reading, but we an additional
write enable pin. It's the standard SRAM pinout, and the timings are the
same as SRAM (though possibly slower).

If it's flash, however, there's a command set to erase and program it.
You write some magic values to a memory location to put it into command mode
and then send it commands for erasing and programming blocks. If you aren't
in command mode it behaves just like a ROM. For example, here's the
datasheet for a 29F040 of 1995:

http://robotics.ee.uwa.edu.au/eyebot/doc/DataSheets/29F040.pdf

Theo

[Ian Field]

"Theo Markettos" <theom...@chiark.greenend.org.uk> wrote in message
news:W8y*fc...@news.chiark.greenend.org.uk...

Thanks - do you know whether there's any books on the subject online?