what was eproms original purpose?

[jbeaton9292]

I was just thinking about this what was the original purpose of the eprom ecu i know what we do with them now but the factory knew nothing of the things we do with them now so why did they install them in some

 

[rough]

I have no clue, also would like to know, I'm thinking the factory used its own proprietary software to image these ecus and the people hacked it, kinda like jail breaking an iPhone or flashing an android.

 

[GSLENK]

IIRC it was for cars early in the production line. They wanted to be able to "tune the car" after the car was completely assembled. The Eeprom allowed this to happen easily. Once the tune was nailed down, they stopped using Eeprom chips and had the ECU's burned correct from the beginning. Hence Eeprom vs non-Eeprom. Had nothing to do with people hacking it (even though tuning as we know it is technically hacking in most cases).

 

[19Eclipse90]

How rare are 1g eprom ecus?

Back in the late 80's and early 90's, automotive microprocessor chips were either mask programmed ROM (they make the transistors for the ones and zeros of the software at the same time as they are making the ones for the processor gates) or fuse based ROM. Once you had good software, including the EPA approved fuel and timing maps you could send the software bits to the microprocessor factory and they would start making MPU chips, and 8 to 12 weeks later you would see parts and if everything was good you could start making ECUs with them.

Since the production line couldn't something like wait 8-12 weeks for custom CPUs the factory would the same ECU design as the development teams used with a interface circuit that could run the software from an external chip (the EPROM) that they could program over and over or in bulk and ship cars. The downside was those ECUs were at least $10 more in just raw parts and may have been several hundred $ more each actual cost. If you making a couple hundred thousand cars that's some real money, so as soon as you can you switch to the cheaper masked programmed MPU part and stop shipping EPROM ECUs. So typically you would see the EPROM ECUs in the early production months and then from time to time as the Just in Time delivery process failed and they needed ECUs to keep the production line running.

It wasn't until 98 or so that the ECUs started getting flash memory (a type of EEPROM) inside the processors allowing the factory and their service arms to update the programming at the plant or in the field.

For cars like the GVR4 there wasn't enough volume to justify a custom masked programed part so all the cars received EPROM ECU's but DSM production levels were such than no year had only EPROM ECUs

 

[jbeaton9292]

Hmmm wow i figured it was some sort of tuning function but wasnt sure what it really did pretty intresting to find out

 

[jbeaton9292]

I have no clue, also would like to know, I'm thinking the factory used its own proprietary software to image these ecus and the people hacked it, kinda like jail breaking an iPhone or flashing an android.

I dont know if its like flashing android as i can do that just fine and im not so sure i could do the ecu eprom reading but then again im not writing the code for the android flashes either so i guess maybe

 

[briansmith]

Lol. There is nothing fancy about eprom ecu's. Pac man was wrote to a eprom. It's old but proven technology. It now "code" it's binary. Or hex. The eprom chip is a primitive flash drive. The "tune" is wrote in hexadecimal and read by the processor chip. The 68hc11 processor chip uses a spacific set of oporation codes via the eprom chip. If you understand the op codes and know the memory addresses for certain sensors you can rewrite the hex to add features or change fuel and timing maps the eprom was not brought about to gene the manufacturer the chance to get the tune "nailed down" it was implemented in the early 1g ecu's because in the event of a warranty failure a remaned ecu could be installed and the eprom sent back. This allows the eprom to be repaired and rechipped for different cars then send out as a different model ecu. There was a few different varieties of tunes on the 1g e931 e952 e954 along with a few I can't remember. Each version was a tune for a different engine. Same goes fpr the 2g car. EB23A eb23b eb23c eb23d eb23e. EB13a b c d e when it was proven that the ecus had no real warranty fail rate. The eprom was ditched for a non eprom where the tune was stored within the ecu itself not in a removable eprom chip

 

[rough]

Lot's of great info!

 

[steve]

Brian, there is no difference between Hexadecimal and Binary, they are just two different representations of a number. Hex is more compact being base 16 rather than base 2 or base 8 (octal).

The code of these early processors was written in hand coded assembly language (a low level symbolic language) due to space and speed issues. The program was then assembled, linked and the result is called machine code, a stream of operation codes (instructions) which the processor directly executes.

As mentioned in the link, the MH6111 processor had mask programmed ROM for program storage. It had a multiplexed data and address bus to reduce pin counts and for development purposes you could add a port expander to the processor and use external RAM and ROM. This adds cost to the computer but makes it easy to write code. Once you have your code production ready you would send it to the FAB and they would make processor chips with your code in the on chip ROM when they turned silicon into microprocessors.

While the MH6(1-3)11 processors are derived from the Motorola 6800 family under license they are not M68HC11 chips. Much of early work was spent deciphering what the instruction set was and once it was recognized as a 6800 family part what differences there were from other mainline 6800 processors.

Keep in mind that this is late 80's implementation of mid 70's computer architecture. There wasn't Flash Memory yet, EEPROM when available was expensive, the most cost effective high volume program storage was mask ROM but it had very long lead times and was expensive in low volume. You change a bit and you would see the new parts in perhaps 3 months later. Programming an EPROM could be done in minutes and that's what the factory did for development and low volume production.