Help! DIY 4 amp L297/6203 driver

[Ross77]

Hi All

Im looking to build a new stepper driver for my mill project. The original board used an L297 driver and 2x L6203 H bridge output stage. I'm hoping to build something similar and have found a few circuits on the net.

I have also found some nice additions to the basic circuit like overload protection for the output chips (good idea since I fried them on the last board ) and varable voltage for VREF to increase Half step torque.

The circuit i have used i heavilly based on one I got from an old thread on cnczone but I'm unsure what the Pic chip dose (i asume it detects the clock pulse and varies the VREF accordingly)

So Question 1. can anyone help with a replacement circuit for the PIC chip as I dont want to use PIC chips for this project.?

And Question 2. Can some check over my version to make sure it works or suggest an alternative?

Thanks in advance