I am seeking help desparately to complete a senior design project. I have read all posting regarding students, searched prior to posting, reviewed the tutorials, and worked on my own extensively. Any help I recieve here will be referenced.

I am using a Philips 89C51RD+ microcontroller to manage a maxium power point tracker circuit. The microcontroller requests 1 byte of information from another device using the serial port and recieves that one byte of information back, which represents the voltage of a battery pack. This voltage byte is used to calculate adjustments to the duty cycle of the circuit. The duty-cycle value is multiplied by a period value of 20us. The resulting value, "time_on" represents how long I will set my output pin P3^4 high and also tells me how long the pin needs to be low which is 20-time_on = time_off. The resulting signal on P3^4 is a square wave with period=20us and varying width. The value used to obtain the time values will change each software run. I am having difficulty writing the function that will create this effect. Originally, I was trying to accomplish this with timers and software loops, but recently I was told it would be easier to do this using the PWM capabilities of my 89C51, however timers are already not a strong point of mine, and I have never handled PWM before. I would appreciate any assistance anyone can provide. I have tried to make as much information available as possible to make it easier. My code thus far is posted here.Thank you and the site is great.