We have the following physical setup:
PowerPMAC CPU in UMAC chassis
ACC-5E3
MACRO fiber link
8 Axis MACRO CPU
ACC-24E2S
Stepper drive
With this configuration, and the default ms0, mi903 of 2258, we cannot modulate the stepper speed very well. As we increase the open loop output (#1 out ), the motor jumps from stopped to rotating at a speed equivalent to a step output frequency of 150 steps/second. This occurs when the output magnitude reaches 1. It appears that with this configuration, the stepper speed is limited to discrete values. The next step is a motor speed of around 300 steps/second.
Changing ms0, mi903 to 2298 (increasing PFM clock divider from 2 to 7) reduces the lowest achievable speed, and reduces the increments for each speed change.
The ACC-5E3 manual states that only the high 16 bits of Gate3.MacroOutA[j][2] are transferred across the MACRO link.
Is there a configuration change we can make on the ACC-24E2S other than the PFM clock divider, to allow better speed modulation? What I would like is for the stepper speed to respond correctly to fractional changes in the motor output command.