PWM protocol?

[jfunk]

Does anyone have or know were I can find info on fords PWM protocol? I've found some stuff on the J1850 Protocol but it's specific to VPW and doesn't say much about PWM.

[Keith@HPTuners]

I believe ford uses J1850 as well... PWM is just how the actual signal is sent across the lines.

I take it your interested in communicating with the PCM and sending/recieving messages though.

[jfunk]

Yeah, PWM is defined under the J1850 protocol. I've found a lot of stuff on the software level like the data packet structure which should cover both VPW and PWM. But, I can't find any hardware level info on PWM.
Since Fords PWM uses a two wire differential bus at 41.6 Kb/s instead of the single wire at 10.4Kb/s like the VPW all the hardware level info I have on VPW doesn't help. :P
I'am trying to find the signal voltage levels, timing requirements, and other info like that. I want to get the info for free because I don't really feel like dishing out the money to SAE for the white papers on J1850.

I want to be able to communicate and hack into the PCM(performance), instrument cluster, Central security module(make my own car alarm), central timer module and other modules connected to the J1850 bus.
;D

[Keith@HPTuners]

I gotcha.. When you do figure that stuff out I hope you'll assist me in building the ford PWM page similar to the GM VPW's.

- Keith

[lndshrk]

Oki Semiconductor makes a chip called the MSM6636

It's the only J1850 PWM i/f chip I know of.

It also has nice descriptive documentation 8)

The general datasheet page is:

http://www.okisemi.com/eu/1.Products/Purpose.html

A more useful document for you might be : ;D

http://www.okisemi.com/jp/datadocs/d...msm6636_ug.pdf

I'm not a "Ford guy" so that's all I can do to help.

Good luck Mr. Phelps.

[jfunk]

Cool! Those PDF's have most of the info I was looking for. Now I can get started! ;D Thanks lndshrk.