L297/298 help please...

Hello all, I am trying to build a stepper controller for a bipolar

2A/Phase stepper motor, but I am having some trouble.

My circuit is like the one on the data sheet

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with some changes.

For one the RC pair on OSC (pin 16) on the L297 produces a frequency of about 14 KHz not 20 as the data sheet shows. (f = 1/ .69 RC). My resistors (RS1 RS2) are .47 ohm 5 watt resistors. I have Enable pin hard wired to +5v, CW/CCW pin hard wired to GND, Control pin wired to

+5V, pins 1,3,and 20 are not connected. The L298 is as shown. Vref is conected to a 1K pot where I can vary the resistance from 0 to 5V (keeping it below 3V as per the data sheet).

The problem is that I can't get the motor to do much. When the motor is still, it squeals unless I turn Vref way down to the point that the motor has almost no holding torque. When I try to make the motor spin (using the printer port on my PC and code i'm writing MSV .NET) it clearly detects the "pulses from my parallel port, but it seems to just

jitter back and forth.

My first question is what is the control pin for? Should I have it high

or low? Also, to drive the motor, should I use a square wave? That is,

should the on time equal the off time? Also, why is my motor changing directions? Any other advice would help alot, and thanks. Lucas

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