A fast and simple PWM question

[qtommer]

I need to invoke the powers of the PWM in the PIC16F877A but after reading the datasheet discovered that it cannot handle a PWM period of 20ms. (50Hz)

My motors (from a previous project) need 50 Hz and hence I would like to inquire if there are any interfacing/any possible methods where my PIC will be able to control a servo with the aforementioned PWM requirement?

Motors are damn expensive in my part of the world=(

 

[crutschow]

Is this an AC motor? PMW is normally used with DC motors and the PWM frequency is typically in the kHz region.

 

[qtommer]

im actually controlling a RC servo...and even in my area, RC servos cost much $$$$$$......
i found out some software control PWM on this site that recommended to break down the 20ms into 20 subsections of 1ms frames but i cant seem to get the algorithm as it is in all in C...and im using assembly...

im guessing that should i want a duty cycle of 10% (2ms) , i would invoke a PWM routine of 2 1ms frames at 100% duty cycle followed by a PWM routine of zero duty cycle 18times?

I hope it's not asking for too much but I would appreciate it if someone could give me a brief "breaking down into 20 sections" assembler code structure for the so I can get started to further progress the code for my application=)

even if there's no code...brief algorithm guidelines would be APPRECIATED ! thanks=)