DIY EPROM programmer

[Trepan]

I have need to program some 27C256 and 27C512 EPROM chips.

I was wondering if anyone knew of a DIY project where I could build the programmer, or is it just cheaper to buy one?

Thanks

[SETEC_Astronomy]

I would like to be able to help you with this but I would need to know more about your requirements for the programmer. The EEPROM chips you specified do not require specialized circuits for programming, all that is needed is a clk and data line that uses the I2c standard. So really a programmer would consist of a 5v power supply, data line and a clk line, nothing more is needed. If you wanted to program these chips using a computer you may want to search google for a hex compatible program that can handle I2c over either your serial or parallel port. I myself would make use of the parallel port for simplicity and low cost of implementation since it requires no additional hardware to get the correct volage levels needed for the EEPROM ICs.

[MrAl]

Hi there,

I looked up the 256 chip and found it is not a serial device.
It seems to have address lines.
Were you looking at a serial device or something?

[SETEC_Astronomy]

my bad, I was thinking of the 27aa series of EEPROMs offered by microchip which are I2c EEPROMs. I used to toy with the 27c series of EPROM (UV erasable) that I scavenged from old equipment. Now that MrAl set me straight the answer to your question doesn't seem so obvious.

EDIT:
I found a few links that may be of some help. I would try to make the programmer and not buy one but that's mainly because I can't afford to buy one. Ebay had a few units for sale if you have the dough to spend.

http://www.qsl.net/iz7ath/web/02_brew/1 ... 07_eng.htm

(useful if you need details on proper programming and erasure procedures)
http://wiki.xtronics.com/index.php/How_EPROMS_Work

[MrAl]

Hi again,

Basically if you build one yourself you can use address counters
to drive the address inputs, clocked by either a switch or the
computer interface. This takes a string of binary counters.
You have to apply a programming pulse of the correct voltage
for the correct amount of time, refer to the data sheet. This
takes a one shot and perhaps a transistor.

The computer interface has to take whatever port signals you are
using and convert your commands to either a program pulse
or data transfer or address counter clock pulse.

The software to drive the computer interface has to take your
data file and read it and send the data to the port, sending the
required commands before and/or after each data entry.
The data would probably be arranged as one line per address
such as:

0x80
0x91
0x32

etc., for an 8 bit data device.

The theory behind these things isnt that hard to understand, but
it does take a little bit of hardware, and the software has to be
written to work with the port and the address counters and
data latch and probably a command interpreter. The command
interpreter can probably be just a 1 of 8 decoder or something
like that, with a latch to hold the command byte.

It should also be possible to accomplish all the above tasks with
a micro controller, except for maybe the address lines, which would
probably still be better done with binary counters, having the uC
reset the counters to start and then pulse them once for each new
address.