At 10:42 AM 20/05/98 +0000, you wrote:
>On Tue, 19 May 1998, Thomas J Macauley wrote:
>
>> Also, while CAN is a good networking system, there are some environments
>> where field busses are NOT a good idea.  I'm still not sure if I like
>> the idea of a network controlling the brakes in a car.
>
>The network that controls the brakes is an add-on that serves the ABS and
>other refinements. If it fails, then the systems remains a pure
>hydraulical brake, as in our grandfather's time ;) Moreover, it is
>GUARANTEED to work if electrics fail TOTALLY. Nothing to fear about, the
>people who built the car had the same idea, and they were MORE afraid than
>you, believe me. From the tiniest engineer and up to the top. And of
>course we are talking about cars, and not TRUCKS (which have some
>pneumatical paranoia attachements for the case, and pneumatic automation
>in the braking section) ;)

This is correct, however you will find that the network used to control the
ABS is separated from the other networks! That's right, there is more than
one network in a car these days, however looms still will exist, as the
major cost of wiring is the dashboard harness, where running (Installing)
the loom is more expensive than the loom itself. For the current time being,
looms will still exist to ancillary items such as tail lights, semiconductor
manufactures have attempted to "Sell" the idea of L.E.D tail lights to the
car makers, but alas a simple globe is cheeper.
As for the ABS, quite correct (Now, but not before*), the ABS controls a
relief bleed valve in the brake caliper.

Also there are more than one from of network protocols used by car makers,
CAN is one (European, by birth), however GM has its own as it found CAN to
be "Unsuitable".

* As for ABS, just ask one European car maker about it, they had reported
problems of ABS not working (It killed the occasional driver), turned out to
be a software problem.

As for PCs crashing, I find that most of these problems are to do with the
actual software that is running, that causes the crash problem, by doing
things such as memory overwrites, null pointers etc. Using infected code
calls to unsupported BIOS type functions etc. One could say that the
operating system should prevent this, AH!, QNX. Or should the software
company recommed a fully tested BIOS and operating system?


Dennis