Tenaja,

Thanks for your comment. That's a good idea - I presume toggling the drive pins will be OK as long as they stay high for the minimum time for my driver - 5uS.

I'll give it a try.

What I want to do next is incorporate a ramp-up/down (for constant accelleration) but can't see how to do it with both motors?

I've done it with one motor OK:
1. Using a list of pulse times held in EEPROM, as in David Benson,s book 'Easy Step'n'.
2. Using a maths routine to calculate the periods - too slow in PBP.

Any ideas how to do it with two motors?

Regards Bill Legge