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Full Version: Modulating stepper speed with ACC-24E2S over MACRO
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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 <n>), 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[i].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.
I think the following "outline" would be the best approach:
1. Enable MLDT mode MI161 – 168, writes to C register once at power on and disable write to C register.
2. Use MI19 = 0 (xfer phase rate). It’s done in background and not phase interrupt but should be fast enough.
3. MI20 (MI21-68 xfer enable) &
4. MI21 – 68 (24 bit xfer format) There’s an X or Y 24 bit transfer FROM and TO format

See the "old" MACRO SRM for details on these:
http://www.deltatau.com/manuals/pdfs/MAC...3273153363