Building a microprocessor based tachometer.Need help!

I am working on a project called "Tacho for microprocessor based drives." I m using 8085.The kit is creating problems in generating interrupts(RST7.5 & RST5.5)Can anybody help with some suggestions on interfacing. Using 8255 as I/O port and 8253 as counter. The phototransistor sends pulses when the motor completes one rev.Speed in rps.

Search for some of my posts (crust) and tachometer. This question has been asked several times and there are very good responses and techniques from myself and others.

The microprocessor prog. is not working. Can you tell me if I can use some digital counter to count the no. of pulses that I get from the phototransistor. I need to display the speed too