can you steer me on the right direction? I just need a hint to how read and write the eepromOriginally Posted by Tom H
can you steer me on the right direction? I just need a hint to how read and write the eeprom
Not sure I know enough about what you are working on to answer, but here is my best shot...
GM ECMs before 1996 use ALDL for communications to the best of my knowledge. They used EPROMs to store code/tables and whatever. The EPROMs were socketed to allow replacement of the code without replacing the whole unit. For these sort of applications you need to buy/build an EPROM programmer and use a black light to erase.
Later ECMs use a combination of ALDL and J1850 VPW --> AKA --> Class II --> AKA --> OBDII. The operations permitted on the two networks depends on the factory code. The one I have been working with permits limited upload of code through the ALDL. The OBDII also permits limited upload. To get complete access to the code, you need to download a program to memory which then gives you full upload. Somewhat confusing but this permitted GM to control who could see what.
One last way to access a 68HC11 is to use the bootstrap option. I am working on one now that gives full capability to reprogram PCMs that are bricked.
Last up, the 68HC11 contains a small EEPROM. In the factory code this stores variables such as serial number and other semi-constants. I am not aware of any of our PCMs that used EEPROM for code. The later units use FLASH. EEPROM would be an improvement form some perspectives as it would allow alteration of the stored code without re-write of all the code.
Cheers,
-Tom
Thanks Tom this help me a lot and this is the best response I have so far, this ecu is a 68hc11 base and I know that the way to read/write is by the aldl, but what i dont know is if the the tables are store on the 68hc11 or on a independent memory chip, if the last is the case then i can read it on my XGPRO OR ON AN XHORSE OR A UPA, is more work but is a starting point to have a bin file
What application was this ECU for? Is it a single 'HC11? I take it that this precedes 1996/OBDII.
I am not sure what "XGPRO OR ON AN XHORSE OR A UPA" are... guessing these interface a PC to the ALDL. I built my own interface but due to limitations in the stock software, it was never much use to me other than understanding the car's network. In my case it is the ALDL that links together the PCM with antilock brakes, DERM (air bags), dash and even the radio.
There is a tiny bit of EEPROM in the 'HC11 however it will never be enough to store the necessary tables and whatnot. You probably need to open the ECM and see if there are socketed chips. In case all chips are soldered, it is probably flash based. If you see a socketed part, it's probably EPROM based. The program I am working on might be workable to give you access to read/write depending on exactly what chips are involved. In any case, you will need to dig a bit deeper to understand enough about it to work with it.
If you post a hi-res picture of the board, I might be able to identify some of the parts for you.
-Tom
20240515_144025.jpg
Hope the pic uploads
Wonder what is under the blue dot marked "CM" if possible, lift the label and post what's under it
-Tom
Just guessing here...
Part at lower left of your image is the O2 sensor interface. Matches the numbers I have and the number of pins. Also the layout looks similar.
I am guessing that the blue dot "CM" part is the processor with on chip EPROM. This might match the 68HC711 E or A types. They have variants that come in 52pin PLCC
Other two large parts have the same part number. I expect they are port expanders used to drive/receive all the I/O
To get further into things, a basic step will be to find out which processor you have. Motorola, Freescale and NXP data is available on the web. Just a guess but probably looking at the 68HC711 or 811 type parts because of the EPROM. If you take the blue dot off, do you find a window? If yes this is for sure EPROM if not it might be a single program part. The cost of packages that let UV light in was high and GM could have chosen the make the part one pop. In this case to get much further you would need to change out the processor. If your part is EEPROM, that's good luck. Once you figure out the variant, the bootstrap mode can be used to upload and later re-program.
Can't see from the picture --> What is under the two aluminum blocks at the top? Guessing power transistors? Perhaps regulators?
-Tom
Posting Permissions
Reply With Quote
Bookmarks