currently I am using the 8051 microcontroller with external eprom..

In order to drive the dc motor (with direction) I use the Pulse width modultion 

thru software control(Assembly language programming). However I am afraid that

they will be overheads and thus alter the pulse timing. My question is 

is the software pwm control reliable?. I understand that port 0 is a latch

and so I vary the duty cycle by setting it high first and at the desire 