Couldnt really find a section for this..

A place For General Chit Chat Etc
User avatar
The1
Posts: 4694
Joined: Mon Jan 04, 2010 10:23 am

Re: Couldnt really find a section for this..

Post by The1 »

ok i had a quick look that's what's on the board, my guess is the 8bit controller writes it's data to the vnram on powerup, then the data gets written back to the controller on poweroff as the nvram was blank when i desoldered and read it.

Image
User avatar
festy
Posts: 1039
Joined: Sat Apr 30, 2011 6:27 pm
cars: Alfa Romeos
Location: Narellan, NSW

Re: Couldnt really find a section for this..

Post by festy »

That doesn't make sense :wtf:
The 80C51 doesn't appear to have internal EPROM.
It's got 4kx8 ROM and 128x8 RAM, but no way of retaining the data held in the external NVRAM - so it must be saving it to the 24C44.
How did you read the 24C44? The chip has a power-on restore EEPROM to RAM function, so I would have assumed there'd be *something* in there...
User avatar
The1
Posts: 4694
Joined: Mon Jan 04, 2010 10:23 am

Re: Couldnt really find a section for this..

Post by The1 »

yeh you'd be right, id be wrong, i didn't even look, my gq-4x didn't have 24c44 so i just tried 24c64 so id say it's a different type chip? i just tried it with that just to see if it'd return something other than blank.
User avatar
festy
Posts: 1039
Joined: Sat Apr 30, 2011 6:27 pm
cars: Alfa Romeos
Location: Narellan, NSW

Re: Couldnt really find a section for this..

Post by festy »

Also - I can't quite make out all the markings on the MCU, in that photo but it looks like a PCF 80C51BH-3-P?
Those don't have a ROM encryption key or security fuses so you should be able to dump the ROM and disassemble, which would show exactly where in the NVRAM the data of interest was, and also should show any NVRAM checksumming that would stop you modifying data.
User avatar
festy
Posts: 1039
Joined: Sat Apr 30, 2011 6:27 pm
cars: Alfa Romeos
Location: Narellan, NSW

Re: Couldnt really find a section for this..

Post by festy »

The1 wrote:yeh you'd be right, id be wrong, i didn't even look, my gq-4x didn't have 24c44 so i just tried 24c64 so id say it's a different type chip? i just tried it with that just to see if it'd return something other than blank.
The 24C64 is just 8 bit serial E2PROM, I'm not surprised your programmer couldn't make sense of the 24C44 which is a 16 bit SRAM with E2PROM backup ;)
I was wondering how you read it, I thought you must have wired up a PIC to dump it or something.
User avatar
antus
Site Admin
Posts: 8237
Joined: Sat Feb 28, 2009 8:34 pm
cars: TX Gemini 2L Twincam
TX Gemini SR20 18psi
Datsun 1200 Ute
Subaru Blitzen '06 EZ30 4th gen, 3.0R Spec B
Contact:

Re: Couldnt really find a section for this..

Post by antus »

yeah its the CAT 24C44... when I did it the guy I was working with bought a weird programmer that did support it, and he was desoldering it to read and write. Finding a programmer that does support was a challenge back then (a few years ago) not sure if there is a newer one now.
Attachments
CAT 24C44 datasheet.pdf
(44.72 KiB) Downloaded 349 times
Have you read the FAQ? For lots of information and links to significant threads see here: http://pcmhacking.net/forums/viewtopic.php?f=7&t=1396
User avatar
The1
Posts: 4694
Joined: Mon Jan 04, 2010 10:23 am

Re: Couldnt really find a section for this..

Post by The1 »

so that nvram is a ram and eprom combo from reading, power up reads eeprom to ram then you'd have to activate store to write back?
User avatar
antus
Site Admin
Posts: 8237
Joined: Sat Feb 28, 2009 8:34 pm
cars: TX Gemini 2L Twincam
TX Gemini SR20 18psi
Datsun 1200 Ute
Subaru Blitzen '06 EZ30 4th gen, 3.0R Spec B
Contact:

Re: Couldnt really find a section for this..

Post by antus »

I think it automatic on power down, so your kms dont ever dissappear and there is only one write cycle when you keyoff

edit: yep,in this application its configured at startup and then it'll do it on power down.

Code: Select all

Once writing/storing is enabled, it will remain enabled
until power to the device is removed, the WRDS instruc-
tion is sent, or an E2PROM store has been executed
Have you read the FAQ? For lots of information and links to significant threads see here: http://pcmhacking.net/forums/viewtopic.php?f=7&t=1396
User avatar
The1
Posts: 4694
Joined: Mon Jan 04, 2010 10:23 am

Re: Couldnt really find a section for this..

Post by The1 »

going through the list of the william about all i can see is 93c46 16bit ones.
User avatar
festy
Posts: 1039
Joined: Sat Apr 30, 2011 6:27 pm
cars: Alfa Romeos
Location: Narellan, NSW

Re: Couldnt really find a section for this..

Post by festy »

Reading/writing should be pretty simple, it wouldn't take much to hook a pic etc up to it and set up a simple serial interface to a pc.
Post Reply