I have built a DC motor speed controller using a nmos dual timer/oscillator
(NE556).  Control voltage is generated by a transistor configured as an
emitter-follower.  The output of the NE556 drives a power darlington
transistor, to which the motor is hooked.  The controller works OK, using a
potentiometer to vary control voltage.  My question is: " does anyone have
any suggestions on how best to use a PIC16f84 to vary speed and motor
direction for this type of DC motor speed controller?"

I am new at this and welcome any suggestions, to include alternate methods
of DC motor control.

Thanks,