freqmod - step pulse timing



Could someone tell me please, does EMC expect the stepper controller to step
on the rising edge or falling edge of the step pulse?  Is Direction valid
for a complete +/- or -/+ step pulse cycle?  What is the minimum step pulse
width?  How long after a step can direction be assumed to be valid?

Reason I ask - My controller seems to miss a step sometimes.  I have my
controller set to half step.  When it powers up, it is on a full step.  I
run EMC and at axis 0.0000 it is on a full step.  I run some of the included
.ngc files and the motor seems to run ok except sometimes I sense a jerk -
usually at slow speeds, and when I return the axis to 0.0000 it stops on a
half step (no backlash programmed in).  It should stop exactly where it
started on a full step.  Note - it's the controller that misses a step not
the motor.

My controller uses a micro to decode step and direction.  It uses an
interrupt on the step signal pin.  I have it set to interrupt on the rising
edge but I could change that easy enough.  After it gets a step interrupt,
it takes maybe 1 or 2us max to save context and get to the interrupt routine
where it checks the direction input and decide which way to step.

Thanks for any help!

Joel






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