Delta Tau GEO BRICK LV User Manual

IC# - Chan# 

0 - 1 

0 - 2 

0 - 3 

0 - 4 

1 - 1 

1 - 2 

1 - 3 

1 - 4 

I8xxx 

IC# - Chan# 

2 - 1 

2 - 2 

2 - 3 

2 - 4 

3 - 1 

3 - 2 

3 - 3 

3 - 4 

I8xxx 

IC# - Chan# 

4 - 1 

4 - 2 

4 - 3 

4 - 4 

5 - 1 

5 - 2 

5 - 3 

5 - 4 

I8xxx 

IC# - Chan# 

6 - 1 

6 - 2 

6 - 3 

6 - 4 

7 - 1 

7 - 2 

7 - 3 

7 - 4 

I8xxx 

IC# - Chan# 

8 - 1 

8 - 2 

8 - 3 

8 - 4 

9 - 1 

9 - 2 

9 - 3 

9 - 4 

I8xxx 

IC# - Chan# 

M0 - 1 

M0 - 2 

 

 

 

 

 

 

Ixx02 

Servo ICs 0 and 1 are on the Turbo PMAC2 itself or on Acc-2E 3U-format stack boards. 
Servo ICs 2 – 9 are on Acc-24x2 or Acc-51E boards. 
Channels 1 – 4 on odd-numbered Servo ICs are Channels 5 – 8 on the dual-IC boards. 

MACRO IC 0 (M0) provides the two pulse channels on the “handwheel port.” 

Feedback Addresses: Ixx03, Ixx04 
Ixx03 tells Turbo PMAC where to look to get its position-loop feedback.  Whether real or simulated 
feedback is used, this location should be that of a processed encoder counter in Turbo PMAC’s encoder 
conversion table.  In a typical setup, Motor xx on Turbo PMAC will use the “xth” entry of the conversion 
table, with addresses $003501 to $0035C0.  These are the default values for Ixx03. 

Ixx04 tells Turbo PMAC where to look to get its velocity-loop feedback.  For the simulated feedback, this 
should be set to the same address as Ixx03 for each motor. 

Output (Frequency) Limit: Ixx69 
Ixx69 controls the maximum pulse frequency for a given PFMCLK frequency.  At the maximum Ixx69 
value of 32,767, the maximum pulse frequency would be one-half of PFMCLK.  However, because the 
shortest pulse cycle is two clock cycles on and two clock cycles off, the maximum pulse frequency can be 
25% of the PFMCLK frequency.  The equation for Ixx69 is: 

=

 

The maximum value of Ixx69 is 25% of 65,536, or 16,384.  If Ixx69 is set higher than this value, and the 
value written to the PFM register exceeds 16,384, the pulse-generating circuitry will drop pulses and the 
frequency will fall. 

For example, with PFMCLK at the default of 9.83 MHz, and a desired maximum frequency of 500 kHz, 
Ixx69 = (0.5 MHz / 9.83 MHz) * 65,536 = 3,333. 

Parameters to Set Up Motor Servo Gains 

If using real feedback sensors, the motor should be tuned as a normal servo motor would be tuned.  If 
feeding the pulse train back into the encoder counter to create a fully electronic loop, the loop response is 
predictable, and the tuning gains can be set by formula as explained here.  In either case, the control loop 
appears to Turbo PMAC to act as a velocity-mode servo drive. 

To create a closed-loop position response with a natural frequency of 25 Hz and a damping ratio of 1 
(suitable for almost all systems), use the gain settings as calculated in the following sections.