Multiprocessor system

[dn]

Clint Corbin wrote:

> I have been thinking about a fuel injection system composed of four 68HC11
> microprocessors.  The first processor would run the ignition system.  It 

I am working (slowly) on an idea like this, but not quite so ambitious,
I think 4 processors is a little overkill.  My system will use 2 for now,
one for ignition and one for fuel.  I know some guys who did a natural 
gas injection system using 4 processors, but only 2 actually ran the
engine, the other 2 were strictly for data aquisition and communications
for developement purposes only.

> There would be two seperate (and identical) fuel injection systems.  Each 
> would control 4 fuel injectors.  For a 12 cylinder engine, one more fuel
> injection subsystem could be added without change to the master controller.

Por Que?  You could just add more injector drivers, unless you want full
sequential.  Seems to me the software would be a nightmare for this kind of
system.

> Another advantage is that you could build and test the ignition system before
> you had to make the rest of the system.  This would at least let you know 

This is exactly what I had in mind, and after I get it running with the
basic system, move on to DIS...

> One question I do have how should I buffer the various signals that need to
> go to multiple modules?  Would I have to?  Would the standard input filtering
> be enough of a buffer to feed up to 4 inputs simultainiously?  I would love

Motorola was good enough to include the SPI interface port on the 'HC11.
This thing is extremely useful, essentially a synchronous serial port 
running at 1Mbit/s!  It can be set up as a master or slave, requires
only 2 wires to transmit data, and you can hang as many devices as you
have chip select lines for on the bus.  You could use a low impedence
wire-AND type of scheme where the comm lines are just pulled up to
VCC, and each device has an open collector transistor to pull the line
low.  Noise is basically impossible on this type of system.  Also, the SPI
is extremely easy to use, you just store a byte into a register and it 
sends it out serially while receiving a byte from the slave at the same time.

As far as the code goes, you could use the 'HC11E2 which has 2k of EEPROM
instead of EPROM.  This should be plenty of code space, since you're
splitting up the operating system into several parts anyway.  You can put a 
header on the circuit board, tied to the RS232 port on the 'HC11, and 
reprogram the EEPROM any time with a laptop.  Don't even have to pull 
the chip to erase or reprogram it.


Regards
dn

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 Darrell A. Norquay              Internet: dn at dlogtech.cuc.ab.ca     
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