Help! DIY 4 amp L297/6203 driver

[irving2008]

The point of the pic is an alternitive clock, the data sheet stats "that if more than L297 is connected then the clocks should be connected to syncronise the circuit", just to the right of the pic is a change over jumper one side grounds pin OSC on the L297 the other wires in the RC oscilliator components 22k and 3n3F. the pin of the pic which is wired to the (top) of v ref pot is a pullup and will have no effect in modulating Vref or anything else
Roger

Roger,

Not sure if you are looking at the same diagram we are, but the PIC very definitely does connect to Vref - the 3.9k resistor and 1k pot are a potential divider to make the max value of Vref = 1v (blue wiring). The PIC clearly has the ability to ground the top of the pot which will drop Vref to about 20% approx (assuming the PIC output is 0.2v) of its set value.

The OSC circuit (red wiring) does indeed have a jumper on it, but thats to enable an external oscillator input for the reasons you suggest, and has no relationship to the PIC or Vref circuit.