hi friends

I am interfacing rotary encoder with microcontroller 89v51rd2

this encoder will generate pulse according to rotation of motor.

this pulse is input of microcontroller.

now my job is start.
i have to generate two pulse ch1 & ch2
1)ch1 is directly copy of encoder
2)ch2 is 90 phase shifted from ch1.

i think here i have to measure duty cycle of input pulse and from that data i will generate ch2.

can any one give me idea of duty cycle measurement.