OBD2 LT1 XDF $EE EEX creation

[sherlock9c1]

Howsabout this: Maybe the smart approach is to get Tom's socketless brick fixer working, then we can start playing with selective writes. I have accumulated a decent stack of PCMs here (of both OBD1 and 2) so I could be a beta tester.

I think for tuning, I really like kur4o's hack of putting the MAF, VE and spark tables in RAM. At least with MAF and VE you could make the LT1 PCM self tuning, then if the selective write works, just flash those to EEPROM shortly after. Just dreaming here...

[Tom H]

then we can start playing with selective writes.

For me, selective writes are no problem IF the location has not been programmed ($FF). When a programming a location that is already programmed, you "over charge" the floating gates. With the thin dielectric there is a possibility (likely ??) that you will punch through. Then it is time to socket...
I could go on, but I won't. Folks have tried this with some success so it seems to work. One should always make the location = $FF first then do an erase verify command. This will tell you if the margin in the location is OK. Otherwise the bit can be intermittent (crash/misoperation/piss off owner) I believe for myself that avoiding this is the right thing but if others accept, OK w me. There are alternatives...

1) Run the SCI at a faster rate. I will test this. In the past I have run at 125K with no issues. I will need to calc the divisor for the 12.(*& crystal we have and do a test or two to find the reasonable limit. Disadvantage is the need to switch baud in the middle of loading. I will look into the bootstrap to see if the "fast" rate could be used. I think this option best.

2) Load through the SPI with a small loader. This is more complex. In a system you need to keep the other cpu happy & quiet. Along with this there are more wires and a complex code sequence. I say no to this. Advantage is it would cover 94-97.

3) use class II at 4x 10.4 (average with half 0s and half 1s)... ~41k or so give/take. Only support for 96-7

There are dozens of other ways but these are the easy ones that need no additional H/W.

I will avoid overwriting programmed locations, if you do this, your mileage may vary.

-Tom

[Tom H]

Hi,
I am working through the class II programming routines... about half done. Ran across an interesting patent some time back, just getting around to reading now. This patent details the SPI operation on our boards. This is of course needed for Eside programming in the class II years. I didn't yet check but may also be needed for the early years (but I think not).

Have a look at:https://patents.google.com/patent/US...=US5023778.pdf

-Tom