M5M51008BP-70LL SRAM CMOS memory workaround/alternatives

Hello all,

I've got an unit that is fitted with M5M51008BP-70LL SRAM memory. I recently went into position where I run out of free space within the chip. Is it possible to upgrade it to a larger size chip?

The processor in the unit is Siemens 80535-N. It also has memory card slot but I was unable to source Panasonic BN-032MC card which appears was the only option for this model.

Looking for a solution to:
1. Backup existing data
2. Expand the memory

May I also note that there is serial connection port at the back of the unit. However, I have failed to establish communication (but it may be bad cable I was using)

I was about to read SRAM chip but I realized as soon as I remove the chip all data will be lost as it needs constant power supply..

Thoughs and ideas?

- - - Updated - - -

Update:
I have now found this line in processor's datasheet:
“The external data memory can be expanded up to 64 Kbytes and can be accessed by instruc-tions that use a 16-bit or an 8-bit address.”
And the SRAM I have appears to be 262 Kbytes if I'm right? So expanding memory no longer is an option.

I'm now thinking of making up SRAM memory card on prototype board. Anyone did this in the past?

Not sure I follow, but it SOUNDS like you've got a 262 Kbyte RAM that only has 64Kbytes used. Is that correct? Are the unused address pins of the RAM connected to the processor? Can you use those address pins in a 'bank-switching' arrangement?

Correct as for the first sentence. As the processor cannot use more than 64Kbytes external memory I think there is nothing that can be done in terms of expanding it.

I have now sourced memory cards but they only appear to be 32 Kbytes in size. Not to mention very expensive.

As the memory card socket is actually a small break-out board, I thought I could make another breakout board which would act as MEMORY CARD.

I would run into another complexity to connect it to PC but atleast I would be able to copy data from one device to another.

So the question now is how to copy data other than memory card. Is it posible to solder battery to the SRAM chip, remove it from the board and then read it with the programmer? Or I'm overthinking?

Hi,

for sure you may use a couple of memory banks.

In a couple of my projects with a 64kB memory space I used a 32k bank as fixed (not bank switching) for use with C# mnagement and the other 32k space was used for 15 x 32k banks (by user software) controlled.
I did address decode and bank witching with a small PLD.

Klaus

Thanks for reply Klaus, but:
1. I am not 100% sure the unused space in the memory is empty
2. I do not have that level knowledge to achieve what you have done in the past

From my point of view it looked easiest to play with memory card connection. But obviously you may see easier way - but I unlikely know how to do it. Would it be safe and reliable?

In any case, it would be ideal to copy current data from the SRAM to be safe if something goes wrong..

How could unaddressable memory NOT be empty? If you can't access it to read, you sure can't access it to write, either, right?

But why would the manufacturer waste money putting a memory four times the size needed on the board? It sounds like there's some information missing. How about a schematic?

As far as building your external memory card with battery backup, that's a kind of messy solution. Why don't you just use flash? Or why don't you get your serial port working?

How could unaddressable memory NOT be empty? If you can't access it to read, you sure can't access it to write, either, right?

Click to expand...

I said so only because of being careful and not knowing the system well enough I cannot be sure. Thank God I didn't pulled out SRAM chip to inspect it from working mashine 8-O

But why would the manufacturer waste money putting a memory four times the size needed on the board? It sounds like there's some information missing. How about a schematic?

Click to expand...

Well, good question. The unit is made by Weetech in Germany around 1997' mark. Most of internals are unecessary high end (seems they have put only top end parts). I do not have a schematics but as per my first post the processor is Siemens 80535-N and the SRAM is Mitsubishi M5M51008BP-70LL. There is also EEPROM chip but I've found only firmware being stored there.

As far as building your external memory card with battery backup, that's a kind of messy solution. Why don't you just use flash? Or why don't you get your serial port working?

Click to expand...

Flash would be much easier? I am not this area specialist, mainly working with wiring looms and we use these units to test products. As for serial port, not sure what format data will be and how I'll be able to use it. Never had my hands on in such environment, started with CAN bus and similar technologies, serial seems to be bit old fashion way, but if someone can provide me some sort of guidance it would be greatly appreciated. :thumbsup:

Even if you do transfer your RAM contents to FLASH or a battery-backed RAM or whatever, THEN what are you going to do? You're going to need some way of reading that memory. Seems to me that a serial port would be the simplest solution. You could use any one of a number of free terminal programs to capture and save your data. If you can write CAN code, you can certainly write a simple UART handler that reads from your RAM and sends it out the serial port.

Update: I have managed to receive data via serial port. Sadly, now I'm lost as the data is not quite readable.

I have attached the file. Maybe someone will be able to steer me into right direction?

I have already tried to load the same file back to the unit but it does not seem to recognize the data.


View attachment CAPTURE.TXT

Hi,

What do you mean with "not readable"?
It is a binary file, so open it with an editor for binary files.

What did you expect?

Klaus

I am simply lost of having the data but not being able to edit it or load it back to the unit.

What editor would people suggest?

The most important part of this is to be able to backup and load it back to the unit all of the data.

Hi,

If you don´t want to view and edit the data, you don´t need an editor, a simple binary file is OK.

But I recommend a HEX file. Intel-HEX or any other. They include address information.


Klaus

Does this means I should change my file type from .txt to .bin or .hex?

And how do I load it back to the unit?

I've been trying HyperTerminal and been unsucessfull.

Hi,

It is a binary file, thus it makes sense to name it ".bin"
If you store it as hex file, then name it ".hex"

But the name will not change it´s contents

Please give useful informations:

I've been trying HyperTerminal and been unsucessfull.

Click to expand...

* what did you try?
* what did you expect?
* what was not like expected?

Klaus

We know essentially nothing. How's capture.txt being received? Are you sure that it holds the intended backup data?

Sorry, I'll try to explain all:

To receive data, I have connected PC to device via RS232 cable, been using HyperTerminal function Capture & I have selected option "Data -> Serial" within device.

In such way I have achieved the file which is attached in the earlier post.

Then,
I have erased device's memory and tried to send this file (Capture) back to the device. I had to select option "Data <- Serial" which means it is receiving data. I have used option "Send text" in HyperTerminal and the device does receive it (I can see bytes counting in the LCD) but when transmission is finished, the device does not recognize it's over. It stays at the screen "...serial..." and shows the amount of bytes received.

In the normal conditions it would go to next screen where you need to select your primary printer output and then save all changes. I do not get to this stage via RS232. I am aware of this screen because I backup my data to the SRAM memory card but it's only 32 KB.

Doing all this because we have two devices, one of them contains very important data but my SRAM card is too small (I think I need twice as big) ant the other one I am able to play around with.


Because the device's processor datasheet says it can only support up to 64KB external memory I have not looked into ways to change the size of it nor I know if it would work due processor capabilities.

There should be instructions for the data backup procedure, expected device to be connected, along with a specification of the used data format.

We see unformatted binary in capture.txt. Unless it uses a specific start sequence, which isn't obvious at first sight, it's not easy to synchronize the reception from a serial stream. The data may be also cut.

Sadly I was unable to find any data, not even manual for this device.

This is WK120 made by Weetech in Germany. But this was around 1998 year so pre-internet boom. Firmware version is 2.17-4 Lab.

I am aware there is software for these devices but again, impossible to find.

I have tried contacting manufacturer but they only suggested to buy new model as they don't support old one's.

We cannot afford to replace 5 devices as they work just perfect apart from this memory issue. Not to forget new devices cost 5k eur+ each.

Thanks for giving some background information. It should be possible to get the backup and restore function working, but you need to understand the expected operation. It might be that the interface is designed to communicate with a specific PC software and the instrument is waiting for a command sequence that isn't coming.

- - - Updated - - -

Worst case solution is to reverse engineer part of the instrument firmware.

I'll try to read out firmware chip as it's fairly easy (thanks to DIP socket) and will post file here.

I just had a thought - what if I connect two devices via serial and try to transfer data from one to another? I'll see if that works.

Could someone have a look at this datasheet ( https://www.b-kainka.de/Daten/Mikros/d80515.pdf ) and confirm maximum external SRAM size? I could be wrong saying it takes up to 64 KB chip.

Thanks for replies

Edit:
Here is the picture of main chip inside device