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Modulating stepper speed with ACC-24E2S over MACRO


wlewis
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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 ), 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.

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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/MACRO%20SRM.pdf?id=635787783273153363

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