Dale Ulan ulan at ee.ualberta.ca
Sun May 22 07:01:08 GMT 1994

> 65%... I'm impressed. Do you think there is enough "head room" (extra memory
> and CPU cycles) to write all the software in C?

Not the C compilers I've seen (the free ones). Maybe the commercial
compilers would work better. I'm sticking to assembler for my stuff
because I can't afford a big commercial compiler...

> Could you share with us your general I/O configuration?

Sure. Here goes:

Timer Ports:

IC1: camshaft position encoder (not presently used)
IC2: crank position # 1
IC3: crank position # 2

OC2,3,4,5: fuel injector control
OC1: ignition control

PD2: ignition route select (#1/#2)
PD3: stepper controller (idle) STEP
PD4: stepper controller (idle) DIRECTION
PD5: stepper controller (idle) LOWPOWER

Port G:
CSPROG used to select a 27C512 EPROM chip, although I used a 27C256.
CSIO1 used to select a 74HC574 latch for output.
The remaining 6 port G lines are used as inputs:
A/C request in,
Start Signal in,
PS Pump pressure,
2 spares.

All 8 outputs from my 74HC574 go to MTP3055EL MOSFETs, which drive:
fan relay
oil cooler fan relay
fuel pump relay
check engine lamp
A/C clutch output
and 3 spares.

the serial port has two modes: a 19200 mode which is used for
my own use, and it actually generates 166 baud data for the old GM
scan tools if you're hooked on to one.

The hardware of the spark system has a built-in 'bypass' mode, where
the timers are left on, and sparks occur when the spark steering
output changes. This is for cranking and the first few seconds of
running. after this, the CPU starts running OC1.


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