crank/cam + ignition/fuel 68332 timing relationships

[Jeff Fisher]

As more and more of my EFI code comes together I'm begining to deal with
timing and TPU issues.  One that I just can't figure out is the
relationship between ignition and fuel injection signals:

If you use a crank sensor, you can set up the PSP (position-synchronized
pulse generator) TPU function to fire the ignition coils every 90 degrees.
No problem. But, I do not see how you can set up this function to fire the
fuel injectors from the crank sensor, since they would inject every other
complete revolution of the crank.  Can you specify angles greater than 360
degrees in PSP?

Likewise, if you go with a cam only sensor, you can set up all of the
injectors using the PSP function, but the coils would have to fire 2 times
for every cam sensor revolution.  Is there a way to make the TPU take care
of rescheduling the PSP event??


I know you could handle this by having the CPU rewrite the configuration of
PSP every time the crank turns over, or every half time the cam turns over.
But this seems wrong.  It defeats the purpose of the TPU being able to
function independantly of the CPU.

How would you do it?



Thanks,
Jeff Fisher