Looking for feedback on stepgen setup

Looking to validate my thoughts on setup here.

For reference, I have:

• A mesa 7i76e
• CL86T v3 Drivers
• 6A Steppers with 1.8deg step angles
• My hal and ini

And some assumptions/assertions/questions I have are:

• Because I have an fpga:
  • I use the HostMot2 driver in a servo thread
  • I don't need to worry about latency (as this is for software stepping)
• The mesa's step frequency is 0 to 500 kHz
  • I need to calculate my steps/in knowing my steps/rev to thread pitch
    • This will become my STEP_SCALE (pulses per inch)
  • The pulses then must be less than (500kHz / 1e6) == .5 per μs? For each motor or all three?
• My drivers Step Pulse times are 2.5 μs, and steps on the falling edge (I think?)
  • I would set the STEPLEN to 2500 and STEPSPACE to 0?
• My drivers direction setup is 5 μs, but I have no idea what the hold time is? 5 μs also?
  • I would set the DIRSETUP to 5000 and DIRHOLD to 5000?

Since the maximum step rate of the drive is 200 KHz
You could set the timing to 2.5 usec step time and
2.5 usec step space so that you do not violate the
maximum frequency. This does have the disadvantage that
it is using the minimum step width. Its probably safer initially
to limit the step rate lower (say 100 KHz) and use 5 usec for both
step time and step space.

 The setup and hold times do not appreciably  affect performance
so there's no disadvantage to making them quite large, say 10 usec, 10 usec

Aha, thanks, didn't catch that the drivers max was 200kHz. And you say 2.5μs step and 0μs space would violate the frequency because that'd be400kHz? And 2.5μs for both would be200kHz?

I've no problem with 'safe' values -- though is my trade-off here only my maximum velocity? And i assume a slightly larger direction times means practically very little for a cnc?

Yes, if you set the step time and step space to 2.5 usec
the stepgen hardware is prevented from violating the
drives 200 KHz maximum step rate limit. How picky the
actual drives are is unknown.

In practice with step motors, its not likely that your maximum
speed will be limited by the step rate, as you can always lower
the steps/turn setting on your drives to get a higher speed at a
given step rate, possibly losing a bit of smoothness.

And yes, the setup and hold times have very little effect on performance
since the only have an effect at reversals (near 0 speed)