Michael,
maybe it's out of your topic but:
1. if you have 80C552 why you don't use its PWM. The 80C552 has two 8-bit resolution, pulse width modulation outputs.
2. To generate pulse is possible to use Timer 2 and its compare logic. This way, you can generate relatively precise pulse.
You can look at: Counter/timer 2 of the 83C552 microcontroller

Vaclav