Delta Tau GEO BRICK LV User Manual

DAC Clock Frequency Control: I7m03, MI903, MI907, MI993 
An I-variable specifies the frequency of the DACCLK signal that controls the rate at which data is 
clocked into the serial DACs on all channels of the Servo IC.  This variable is I7m03 for a Turbo 
PMAC’s Servo IC m.  If the IC is part of a MACRO Station, the variable is MI903, MI907, or MI993.  
The default DACCLK frequency of 4.92 MHz is appropriate for all DACs used by Delta Tau.  This 
variable also controls other clock frequencies for the Servo IC; if you change the value of this variable, 
make sure to keep the DACCLK frequency the same. 
DAC Strobe Control: I7m05, MI905, MI909, MI999 
A PMAC2-style Servo IC generates a common DAC strobe word for all four channels on the IC.  It does 
this by shifting out a 24-bit word each phase cycle, one bit per DAC clock cycle, most significant bit first.  
I7m05 contains this word for the channels on a Turbo PMAC’s Servo IC m.  If the IC is part of a 
MACRO Station, the variable is MI905, MI909, or MI999.  The default value of $7FFFC0 is suitable for 
use with the 18-bit DACs used by Delta Tau. 
Output Mode Control: I7mn6, MI916 
I7mn6 must be set to 1 or 3 to specify that outputs A and B for Servo IC m Channel n are in DAC mode, 
not PWM.  (On a MACRO Station, this is controlled by node-specific variable MI916.)  A setting of 1 
puts output C (not used for servo or commutation tasks in this mode) in PWM mode; a setting of 3 puts 
output C in PFM mode. 
Output Inversion Control: I7mn7, MI917 
I7mn7 controls whether or not the serial data streams to the DACs on Servo IC m Channel n are inverted.  
(On a MACRO Station, this is controlled by node-specific variable MI917.)  The default value of 0 (non-
inverted) is suitable for use with any of the Delta Tau analog outputs.  Inverting the bits of the serial data 
stream has the effect of negating the DAC voltage.  In a servo algorithm this changes the polarity match 
between output and input, which would produce a dangerous runaway condition if the system were 
working properly before the inversion. 

Motor Parameter Setup 

Commutation Enable/Disable: Ixx01 
Bit 0 of Ixx01 must be set to 0 to disable the commutation algorithms for Motor xx.  Commutation is 
performed in the drive or the motor in this mode of operation.  Bit 1 of Ixx01 is set to 0 to specify that the 
output register whose address is specified in Ixx02 is a Y-register.  Virtually all of the output devices 
usable in this mode are located in Y-registers, so usually Ixx01 is left at the default value of 0 here. 
Command Output Address: Ixx02 
Ixx02 instructs Turbo PMAC where to place its output commands for Motor xx by specifying the address.  
The default values of Ixx02 use the DAC register for the Machine Interface Channel matching the motor. 
Ixx02 seldom needs to be changed from the default value for DAC applications.  Typically, the values 
used are: 
PMAC-Style Servo IC Command Output Addresses (Y-registers) 

IC# - Chan# 

0 - 1 

0 - 2 

0 - 3 

0 - 4 

1 - 1 

1 - 2 

1 - 3 

1 - 4 

Ixx02 

IC# - Chan# 

2 - 1 

2 - 2 

2 - 3 

2 - 4 

3 - 1 

3 - 2 

3 - 3 

3 - 4 

Ixx02 

IC# - Chan# 

4 - 1 

4 - 2 

4 - 3 

4 - 4 

5 - 1 

5 - 2 

5 - 3 

5 - 4 

Ixx02 

IC# - Chan# 

6 - 1 

6 - 2 

6 - 3 

6 - 4 

7 - 1 

7 - 2 

7 - 3 

7 - 4 

Ixx02 

IC# - Chan# 

8 - 1 

8 - 2 

8 - 3 

8 - 4 

9 - 1 

9 - 2 

9 - 3 

9 - 4 

Ixx02 

Servo ICs 0 and 1 are on the Turbo PMAC itself. 
Servo ICs 2 – 9 are on Acc-24P/V or Acc-51P boards. 

Channels 1 – 4 on odd-numbered Servo ICs are Channels 5 – 8 on the boards.