Hi Guys:

I'm working on a "tractor performance monitor" from a farm tractor. It
uses an 6803U4 micro and I gather that the main program is stored on a
TC5518 static ram which is battery backed up. The problem came about
when the lithium cell went dead and the static ram lost it's contents.
I do have another working monitor, but does anyone know a way to read
it while it's still on the board? The board was manufactured in 1988.

I was thinking about soldering a 3 volt source to the ground and Vcc
leads, and then use my pocket programmer (II) to read the good one?
This static ram chip is pin for pin compatible with a 2716 eprom!

Can anyone suggest any other means of extracting the data, and
reburning it onto the original 5518?

If you could, also send me a reply to "tedd at ve3tjd dot com".

Thanks for any assistance.

Tedd, VE3TJD

On 25 Mar 2006 09:06:03 -0800, "ve3tjd" put finger
to keyboard and composed:

Hi Guys:

I'm working on a "tractor performance monitor" from a farm tractor. It
uses an 6803U4 micro and I gather that the main program is stored on a
TC5518 static ram which is battery backed up. The problem came about
when the lithium cell went dead and the static ram lost it's contents.
I do have another working monitor, but does anyone know a way to read
it while it's still on the board? The board was manufactured in 1988.

I was thinking about soldering a 3 volt source to the ground and Vcc
leads, and then use my pocket programmer (II) to read the good one?
This static ram chip is pin for pin compatible with a 2716 eprom!

Can anyone suggest any other means of extracting the data, and
reburning it onto the original 5518?

If you could, also send me a reply to "tedd at ve3tjd dot com".

Thanks for any assistance.

Tedd, VE3TJD

Is the uP socketed? If so, remove it. Then wire the address and data
pins of your pocket programmer to the uP socket, and the CS pin to the
CS of the SRAM (or to the uP socket, if applicable). Connect the OE*
pin of the programmer to the R/W pin of the SRAM, through an inverter
if necessary. Now read the data as you would for a 2716 EPROM.

When writing the data, you may be able to "program" the SRAM as you
would a 2716 EPROM or a 2816 EEPROM - just don't connect the Vpp pin.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

On 25 Mar 2006 09:06:03 -0800, "ve3tjd" wrote:

Hi Guys:

I'm working on a "tractor performance monitor" from a farm tractor. It
uses an 6803U4 micro and I gather that the main program is stored on a
TC5518 static ram which is battery backed up. The problem came about
when the lithium cell went dead and the static ram lost it's contents.
I do have another working monitor, but does anyone know a way to read
it while it's still on the board? The board was manufactured in 1988.

I would have thought it /extremely/ unlikely that any manufacturer (especially
of a unit to be used in the wild) would trust his program to RAM. Are you
certain that there is no ROM (with the RAM being used as data storage)?

Geo

Franc Zabkar wrote:
On 25 Mar 2006 09:06:03 -0800, "ve3tjd" put finger
to keyboard and composed:

Hi Guys:

I'm working on a "tractor performance monitor" from a farm tractor. It
uses an 6803U4 micro and I gather that the main program is stored on a
TC5518 static ram which is battery backed up. The problem came about
when the lithium cell went dead and the static ram lost it's contents.
I do have another working monitor, but does anyone know a way to read
it while it's still on the board? The board was manufactured in 1988.

I was thinking about soldering a 3 volt source to the ground and Vcc
leads, and then use my pocket programmer (II) to read the good one?
This static ram chip is pin for pin compatible with a 2716 eprom!

Can anyone suggest any other means of extracting the data, and
reburning it onto the original 5518?

If you could, also send me a reply to "tedd at ve3tjd dot com".

Thanks for any assistance.

Tedd, VE3TJD

Is the uP socketed? If so, remove it. Then wire the address and data
pins of your pocket programmer to the uP socket, and the CS pin to the
CS of the SRAM (or to the uP socket, if applicable). Connect the OE*
pin of the programmer to the R/W pin of the SRAM, through an inverter
if necessary. Now read the data as you would for a 2716 EPROM.

When writing the data, you may be able to "program" the SRAM as you
would a 2716 EPROM or a 2816 EEPROM - just don't connect the Vpp pin.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

On Sun, 26 Mar 2006 16:55:06 GMT, Geo put
finger to keyboard and composed:

On 25 Mar 2006 09:06:03 -0800, "ve3tjd" wrote:

Hi Guys:

I'm working on a "tractor performance monitor" from a farm tractor. It
uses an 6803U4 micro and I gather that the main program is stored on a
TC5518 static ram which is battery backed up. The problem came about
when the lithium cell went dead and the static ram lost it's contents.
I do have another working monitor, but does anyone know a way to read
it while it's still on the board? The board was manufactured in 1988.

I would have thought it /extremely/ unlikely that any manufacturer (especially
of a unit to be used in the wild) would trust his program to RAM. Are you
certain that there is no ROM (with the RAM being used as data storage)?

Geo

25 years ago a colleague was involved in the design of a RAM based
point-of-sale system. I considered it a reprehensible product at the
time and I still do.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Hi Franc:

Thanks for your input. First, I would like to reply to Geos reply.
There is a 2764 right next to the SRAM, but I've tried to read the
eprom and it contains no data. On the working unit I have, I took
another 2764 (NOT THE ORIGINAL!!) and erased it (all FF's) and
reinstalled it and it still worked normally, telling me the code isn't
on the 2764.What is the purpose of the 2764....I don't know.

The uP isn't socketed, so grabbing the address and data lines from this
angle won't work. I socketed the broken units uP as I thought that it
was shot, so once I get the data OFF of the good unit, programming
should be fine.

From the data sheet of the 5518, they say it's a drop in replacement
for the 2716. Do you think the uP address and data lines would cause
too much of a load for the programmer to allow me to try and read it
while the uP is in place?

Why am I so worried.... well, these boards are no longer made anymore
and I don't want to kill the good one by trying to fix the bad one! No
schematics are available (the board was made by TRW in England), so
without reverse engineering the 4 layer board, I think we have to use
common sense with the layout of the "system".

The easiest thing to do would be to solder leads onto the SRAM while
it's in the board, and connect them to the programmer for
reading.That's why I ask if you think it will hurt to leave the uP in
place.

Thanks again guys,

Tedd, VE3TJD

On 30 Mar 2006 06:22:03 -0800, "ve3tjd" put finger
to keyboard and composed:

Hi Franc:

Thanks for your input. First, I would like to reply to Geos reply.
There is a 2764 right next to the SRAM, but I've tried to read the
eprom and it contains no data. On the working unit I have, I took
another 2764 (NOT THE ORIGINAL!!) and erased it (all FF's) and
reinstalled it and it still worked normally, telling me the code isn't
on the 2764.

If you remove the 2764, does the device still work?

What is the purpose of the 2764....I don't know.

Is it possible that the "dummy" 2764 could be a place holder for a
diagnostic EPROM??? Could such a chip be used to initialise the SRAM
with factory defaults??? Once the SRAM is initialised with functional
code, could the EPROM be replaced with an "all-ones" dummy that would
cause the uP to cycle through its addresses until it hits the RAM
code???

The uP isn't socketed, so grabbing the address and data lines from this
angle won't work. I socketed the broken units uP as I thought that it
was shot, so once I get the data OFF of the good unit, programming
should be fine.

From the data sheet of the 5518, they say it's a drop in replacement
for the 2716. Do you think the uP address and data lines would cause
too much of a load for the programmer to allow me to try and read it
while the uP is in place?

I don't know, but you would need to ensure that the uP was in reset
mode so that its address and data lines would be high-Z.

Why am I so worried.... well, these boards are no longer made anymore
and I don't want to kill the good one by trying to fix the bad one! No
schematics are available (the board was made by TRW in England), so
without reverse engineering the 4 layer board, I think we have to use
common sense with the layout of the "system".

The easiest thing to do would be to solder leads onto the SRAM while
it's in the board, and connect them to the programmer for
reading.That's why I ask if you think it will hurt to leave the uP in
place.

I'd experiment by reading and writing the RAM in the bad board.

Thanks again guys,

Tedd, VE3TJD

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.