In article ,
Peter Parry wrote:

As far as I have worked out so far (and this may not be correct
as the tracks on the PCB's I have are difficult to trace) is that
PA0 and PA1 on the microcontroller (A Holtek HT48R05A one time
programmable) go to pins 1 and 8 on the TTD6108. Of the other
TTD6108 pins 3 and 6 go to the motor. Pins 4 and 5 are -ve and
pins 2 and 7 are +ve. I'd guess 4&5 and 2&7 are also used for
simple heatsinking looking at the PCB layout.

I've seen a similar 8-pin motor driver chip... somewhere.

Pins 1 and 8 inputs are Direction command, plus the variable
pulse-width clock from the uP. Pins could be either way round.

Pins 3 and 6 are the outputs from an H-bridge, diagonal pairs
chosen by DIR, clocked by the PWM input. There might also
be 4x (Schottky?) diodes on 3 and 6 to clamp the back emf
from the motor's inductance.

If it is an 8-pin DIP package, reckon on a running motor
current of no more than about 100mA.

With such a simple driver chip, smoothly controlling a motor
can require considerable software in the PIC. See Microchip
App Note DS00532B "Servo Control of a DC Brush Motor".

--
Tony Williams.