I've got a head-scratcher in the last stages of a gyro project

The gyro puts out 38k4 data bursts at the rate of 75 - 77 bursts
per second. The information in the data is converted to a number
of pulses that are sent to motor drivers. Everything is working....

.....except. The motors really perform best when supplied with
evenly-spaced pulses. At present each motor is set to require
1200 pulses to move a gearbox 1 degree

The problem is that the bursts (as measured from the end of the
fifth byte in one to the end of the fifth byte in the next) are not evenly
spread, and can be anywhere from 11 to 14ms apart.

The first version used a single F877 to read the data and generate
the pulses. To do this I had to take the worst-case timing of 8ms free
time for motor pulses (which may be only a few us apart) before the
micro had to return to picking up data. This meant there could be up
to 6ms when the motor wasn't receiving pulses, which caused very
unacceptable jittering. Now the circuit has been split up into an F628
to read data and 3 others - one for an LCD and one each for taking
the calculated spacing from the reader to generate pulses. However,
as can be seen in this diagram

http://home.clear.net.nz/pages/joecolquitt/timeline.html

the problem has arisen again, although hopefully there is better
hardware in place now. I'm trying not to think of it as "re-arranging
the deck chairs on the Titanic". What will happen is that a short
interval following a long interval will cause a driver PIC to still be
in the throes of putting out pulses when it is told to stop that and
pick up new data

The only way I can see out of this is to cause an IRQ on the driver
PIC and temporarily suspend its pulse activities whilst it picks up
that data, and then uses the new spacing at the end of the current
run of pulses

This sounds workable. Any reason why not, or better solutions ?

Losing a few pulses here and there shouldn't (touch wood) be too
much of an issue. I thought of taking the serial data and re-transmitting
it at a more regular rate, but I don't think that will work out because
of the unpredictable nature of the gyro's timing. Sooner or later the
PIC and gyro will get out of synch

TIA

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