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I want to read/write to an SST 31LF041A FlashRAM chip

 
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The Robman
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PostPosted: Fri Oct 17, 2003 2:24 pm    Post subject: I want to read/write to an SST 31LF041A FlashRAM chip Reply with quote

The Mosaic / Director remote uses an SST 31LF041A memory chip, rather than an EEPROM, to store it's settings, upgrades, etc.

I'd like to be able to read/write to this in order to reverse engineer the memory layout. This remote doesn't have a 6-pin connector, so the ultimate goal would be to provide tools to let the users program the remote via the modem, using WAV files.

So, I expect that I will need to solder wires onto the chip itself to fashion a new interface of some sort, which I can do, but I would need someone to write a program to handle the reading and writing. Plus, I guess you'd have to design the interface so that you know which pins do what.

Is this something anyone here can help out with?

Btw, I have loaded the datasheet for this chip, along with a bunch of other relevant files, to the "Mosaic" folder in the JP1-KM file section.
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PostPosted: Sat Oct 18, 2003 7:50 am    Post subject: Reply with quote

Rob,
From your pictures the remote already has a card edge connector - J2. An offhand guess is that this is used to access the flash memory at least. To access the flash the interface would be considerably more complicated than the JP1 interface for the I2C devices.

Joe.
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PostPosted: Mon Oct 20, 2003 6:41 am    Post subject: Reply with quote

Rob,
I've looked at the information you put under Mosaic. I feel that one could interface to the remote using the J2 connector using the USB.

The J2 connector would need to be ohmed out so we could use it to connect to the remote.

Since the flash/ram is 512k , the download/upload time using Delcoms USB would take time. Using the time I measured w/ JP1's EEPROM download (about 3 secs). (512k/2k)*3 = 768 secs = 12.8 mins.

Hardware designed to interface Delcoms USB to the J2 memory buss. I have some thoughts on this and I think it could be done w/o controlling the whole thing through the USB which would slow down the download/upload considerably more.

A faster approach would be a USB chip that could access the J2 buss locally and sending bigger packets (64 byte vs 8 byte) through the USB. The Cypress EZ-USB looks interesting. But it would take time to figure out how to use it to make sure it could be used for this.

Now as for the memory map of the remote I have some thoughts on that. I feel that the flash has the remotes RISC operational code as well as the remotes library info in it. Why else would one need a 512k flash eeprom/sram chip. So this would need to be figured out.

Well I'll send you this to get some feedback to see what you think.

Joe.
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The Robman
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PostPosted: Mon Oct 20, 2003 12:46 pm    Post subject: Reply with quote

Hi Joe,
Thanks for helping out with this. Here's the situation, I have successfully decoded all the data in the WAV files that are used to upgrade the Mosaic, except for the 3rd and 4th bytes. This is not a major problem because those bytes are always set to "44 44" in all the upgrades that we've seen.

I'm hoping that ths data is the address of the upgrade section, which would mean (in theory) that we could change it to be a different address if we wanted to load macros, key moves, etc via a WAV file.

To this end, I'd like to see a memory dump from the flash chip so I can reverse engineer the layout. So, the fact that the dumping process might be very slow is not a problem, it's not my goal to make this process universally available (unless it's easy to do). My goal is just to take enough dumps to reverse engineer the layout and then provide the ability for people to update their Mosaics via the modem.

I don't mind making whatever hardware modifications might be required to my Mosaic to get this done.
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PostPosted: Mon Oct 20, 2003 1:27 pm    Post subject: Reply with quote

Rob,
If I'm right re: the J2 card edge connector then to get the flash you should not need to modify the Mosaic at all. Are you just wanting to read the flash??, or read and write it?

Joe.
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The Robman
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PostPosted: Mon Oct 20, 2003 3:15 pm    Post subject: Reply with quote

I'll take what I can get, but my primary goal is just to read it. If I see something in the format that tends to confirm that "44 44" is either the address where the upgrades get written or is used to calculate the address, I will be able to write to it using the modem.

I assume this is the J2 edge you are referring to...



How were you thinking of reading it? What is a Delcoms USB?
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Rob
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PostPosted: Mon Oct 20, 2003 4:09 pm    Post subject: Reply with quote

Rob,
I'm not saying we can't write to it. I was just checking from what you said and I wanted to confirm. I got the idea you were just talking about reading. Handling both doen'st seem to be a problem. I just want to make sure of what is needed at the start. Its easier than changing things later.

RE: J2 edge connector. Yes the bottom right edge connector is what I think interfaces w/ the Mosaic's flash. I'm refering this as the J2 buss. Are you up to ohming the J2 pins to the RISC chip?. If not what is the posibility of you loaning me the Mosaic remote so I can do it?.

The Delcom USB is the chip that is used w/ the JP1 USB interface. I propose using this w/ some interface chips to manage the J2 buss on the Mosaic remote. I'm drawing some schematics for this interface now to make sure I can do what is needed.

Let me get the design for the interface better in mind, then we can talk re: ohming the J2 etc. For if your open to loaning me the remote then I can to that and test the interface here. This would give us a known, which is a good thing. Debugging hardware remotely would be rather hard, not imposible, just rather difficult.

Joe.
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The Robman
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PostPosted: Mon Oct 20, 2003 4:23 pm    Post subject: Reply with quote

Absolutely, you can borrow the remote to do your thang, drop me a line off-line
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