Electronics > RF, Microwave, Ham Radio

Programming volatile memory boards in older Icom Rigs and radio upgrades

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Radio Tech:
Hello all.
Some of the older Icom HF radios use a RAM board that holds the factory memory like the IC-745 and IC-751.  When the battery goes dead on these boards the factory program is lost and your radio becomes a brick.  The battery has a life of about 7 years but can be changed out. If not done correctly you lose the memory, again you end up with a brick.

A few folks have made a non volatile replacement board to solve this problem. Cost around 70 bucks US or so. Not bad no?

Anyway years ago I was able to read the memory out of one of these boards for the IC-745, This was by using the N2CBU DIY programmer.  This was a dos base programmer that using the parallel port on you old pc.  The programmer uses a CD4040, a 7805 regulator and a couple of caps.  It worked OK for reading the content of the ram. I never tried programming the unit.

What this is all about?
I am not the best when it comes to designing programmers. But I like to build something that is modern to work with today's computers.  I like to build a programmer that would be able to plug into a usb port, read the content of the ram then save it. And the ability to send the data back to the chip.

Perhaps someone with a bit more knowledge of modern programming can point me in the right direction. I am attaching the old files used to do this.

martinator:
You can use something like the FM16W08 to replace your sram. You need to buy a soic28 to dip adapter to make programming easier,rearrange the address and data pins to match whichever application you have in mind and make a little circuit that pulses the chip enable after every address has been set up. Then you can read and write it like an eprom with a normal eprom programmer. I have also read out battery backed srams as eproms. You need to make adapters of course.You shouldn't need to build any special equipment, just buy a half decent eprom programmer.

Radio Tech:

--- Quote from: martinator on December 10, 2017, 05:29:10 pm ---You can use something like the FM16W08 to replace your sram. You need to buy a soic28 to dip adapter to make programming easier,rearrange the address and data pins to match whichever application you have in mind and make a little circuit that pulses the chip enable after every address has been set up. Then you can read and write it like an eprom with a normal eprom programmer. I have also read out battery backed srams as eproms. You need to make adapters of course.You shouldn't need to build any special equipment, just buy a half decent eprom programmer.

--- End quote ---

From what I read is replacing the chip on the original board with a FM16W08?
That does not solve the problem. We still have to have a ram dump from the original chip. It cannot be removed from the board due to the memory is held there by the battery back up.  So still have to build the interface to read this memory.
If this is what you are saying. Remember, I am no programmer.

German_EE:
From what I have found there are two different versions of this board. The old version uses a 1K x 8 SRAM together with a HD7432 IC but the new version uses a 2K x 8 SRAM and not much else. Are schematics of these RAM boards available because I have no idea what the HD7432 is doing?

As for reading the chip, apply 5V and ground to the right pins and monitor the four data lines. A binary counter or a set of eleven switches can be used to step through all 1024 addresses as you write them down. Before you start though you REALLY need to establish the function of pin 8 J17, is (WR) a write pin or write protect?

AF6LJ:
Over on the Icom 745 Yahoo group someone published a memory dump of the contents of the ram chip. For those who don't know radios like the IC-745, 751, IC-R70 and a few others contain set up information in volital ram that is battery backed-up...
A couple of decades ago the folks over at PIEXX built and still market a replacement memory board that works in all these radios. One board that contains the microcode for all the Icom radios that used this module. https://www.piexx.com/?main_page=product_info&products_id=26

It should be possible to build an adapter that will allow the contents of the ram board to be dumped into one of those old school E-Prom programmers.
I have a couple of those RAM boards around here and it has been my experience the battery lasts for better than fifteen years.

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