I have made great progress in reverse engineering AFMs, ECUs and other
funny business in the Digifant injection system. It's classic 80's
embedded CPU technology.

I pulled apart a bad ECU to use part from to build a "sniffer". It was
interesting to see how they did it. Here is a quick explanation:

The "brain" is a standard 6803U4PV. It's a common 80's embedded
microcontroller. Not sure what the differences are in the U4PV version,
because I can't find a datasheet on the 'net. On the CPU daughterboard
there is also a Parallel Interface Adapter, some glue logic, and a 2732B
EPROM. The version label on this one is "FAEB02 02. 02". Anyone have an
ECU open, and can tell me what their's says?

On the main board, the interesting semiconductors are a Toshiba TA7900S
regulator/watchdog with PNP shunt transistor (BD438). Across the heat sink
is also a BD647 NPN Darlington, a Motorola TE2369 (Which I can't find,
probably a house number. Anyone know what this is?), and a BT151-500R
Thyristor. The big chip near the center is an Analog to Digital converter.
Add to that some small signal transistors, couple of op amp/comparators,
and finally a "Peripheral Clamping Array" on the input to the PIA/CPE to
condition signals.

These ECUs make magasquirts look simple. ;)

More on AFM spring adjustments in a bit.

Jon