[TenTec] Corsair II UV EPROM failure
raf_3 at msn.com
Sat Feb 15 22:33:01 EST 2014
Of course you're right, the UV is used only to erase the resident/existing program on a UV PROM. I knew that, and what I intended to convey to Clayton was that the PROM portion of the MC68705P3S is UV Erasable (not programmable), rather than Electrically Erasable.
Replacing the term "programmable" with "PROM" in my original post reading " UV programmable, rather that EE programmable", would have accomplished my original intent, and accurately discriminated between the two subject methods used to erase PROM programs for the purpose of establishing fixturization required to "clean" PROMs before programming.
I like your "cheaper and easier" option. Volunteers?
----- Original Message -----
From: geoffrey mendelson<mailto:geoffreymendelson at gmail.com>
To: Discussion of Ten-Tec Equipment<mailto:tentec at contesting.com>
Sent: Saturday, February 15, 2014 12:03 AM
Subject: Re: [TenTec] Corsair II UV EPROM failure
On 2/15/2014 3:12 AM, A R wrote:
> Oh, man! Clayton, you're my hero. The prom is a 28-pin, and is UV programmable, rather that EE programmable. I believe the programming of my prom is good. It's just an input gate that's stuck low. If that's not a problem for downloading (if input gate states are not needed), then my prom should be good for acquiring the program.
The UV applies to the E not the PROM part of the name. To be exact, the
chip is a microprocessor with a UV erasable PROM attached. To erase the
contents of the PROM in the package, you expose it to high intensity UV
Programming the chip is unfortunately far more complex.
First you program a 2764 EPROM (also UV erased, but not relevant to
programming the microprocessor) with the desired data. 2764 chips are
relatively easy to find, you can get all you want used, erased, and
tested for under $2 each on eBay including postage. They are programmed
with the under $50 programmers you see on eBay. Although if I had to do
it again, I would spend $150 on a USB connected Wilem programmer with
the complete kit of device adapters, but I digress.
The hard part is transferring data from the 2764 chip to the
microprocessor. That is accomplished with a special programming device
that boots up the microprocessor, and sets the program bit on. The
microprocessor boot code senses this bit, and reads data from the
attached 2764 and copies it to the chip.
If you try to program the microprocessor without a 2764, it will program
it with worthless (I think all FF) data, you have to erase it (with the
UV light) and start over.
The second link to a programmer is actually to a device that copies the
EPROM part of the chip to SDRAM and rewrites it to a fresh chip, There
are ways mentioned, but not detailed, to copy that data to a PC, so you
can program more than one, or archive it for later use.
Here are some useful links:
And while you are at it, a UV eraser sells for under $20 on eBay.
Basically if you are handy with a soldering iron, have some computer
savvy, and want to do something new, you can get the whole setup for
around $100. Obviously it would be cheaper and easier to find someone
who knows what they are doing already, and has all the equipment.
Geoffrey S. Mendelson 4X1GM/N3OWJ
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