Multiplex bus for cars.

[Steve=Ravet%Prj=Eng%PCPD=Hou at bangate.compaq.com]

If you get the EDN Products edition (just came out today), there is an article 
about a standard bus that SAE has adopted for communication between sensors, 
controllers, instrument cluster, etc.  It is a one or two wire serial bus 
using variable pulse width modulation.  The one wire implementation was 
developed by GM and has a data rate of 10.4 kbits/sec.  The two wire 
implementation comes from Ford and has a data rate of 41.6 kbits/sec.  Harris 
Semiconductor makes a two chip set to interface to the bus.  One handles 
contention and frames packets.  This chip operates from -40C to +125C, and 
has protection against transients, ESD, and reverse battery connection.  The 
other provides a byte-level interface to a microprocessor.  This second chip 
is available in a "smart" verison that includes a 68HC05 core.

The standards are:  SAE J1850:   physical link layer and message structure.
		    SAE J2178/1: describes actual messages
		    others that the article only mentioned.

California already is requiring all car manufacturers to use a common bus to 
provide emmission data to an external tool.  The rest of the US will probably 
follow suit eventually.  Sounds like there will soon be "smart" sensors that 
interface directly to the bus, eliminating the need for A/D converters, etc.

Harris's address is:
Harris Semiconductor
724 US Hwy 202
Somerville, NJ 08876

No phone number was listed, and there was no "circle xyz" for more information 
number.  Thought ya'll might find this interesting.

--steve