21 Apr
2012
21 Apr
'12
12:02 p.m.
I'm thinkering to build an small Epromer for just
one single sort
of Eproms (Am27C291/CY7C291..) and I'm desingning in a =B5A723 currently.
What about his chip? It is old like stoneage and still in production..
I was amazed to discover there's even an RoHS-compliant version of the
TO110 (10 lead metal can) one. I needed to repalce such a device on a PCB
that had 10 pads in a circle (so kludging the DIL version in would haev
been a problem). It wasn't cheap, but at least I could stil lget it.
Oh, the device.... An HP11305 disk controller for the HP9830. One day
I'll get the 'cable' to link the computer nad controller and then I can
really have some fun.
Unfortunately I'm unable to emulate it's
functionality with the Amtega32
that will be go in that promer (No, Im not going to build an buck convert=
er
out of an Atmega Timer), but for sure I'm generating the program
pulse length not with a 555...
My first EPROM programmer, which I built about 25 years ago couldn't yse
a microcontrolelr or even a microprocessor. There were no
microcontrolelrs abck then that you could program with an SPI or JTAG
interfave, they all programemd a bit like EPROMs. And of course if I'd
used a microprocessor I'd haev needed an EPROM to store the cotnrol
program. The problem being that without a programmmer, there was no way
for me to program that EPROM or microcontroller...
Anywy, it ended up as a couple of boars of logic ICs. I think I used a
74121 to generate the programming pulse. Not having a logic analyser at
the time, or even a well-calibrated 'scope, I set the pusle width by
clocking the input to the '121 at a known frequency (I think I divided
down a crystal) and measured the duty cycle of the output by the simple
method of measuring the average voltage there.
Amazingly the thing worked, I prgrammed many EPROMs on it...
-tony