Delta Tau GEO BRICK LV User Manual

If you have a position sensor for the motor that is absolute over the entire range of travel for the motor, 
you can use motor variables Ixx10 and Ixx95 to tell Turbo PMAC where to read this absolute position 
data, and how to interpret the format, respectively.  This does not have to be the same register or even the 
same sensor that is selected for ongoing position feedback with Ixx03.  If Ixx10 is left at its default value 
of 0, no absolute position read will be performed for the motor, and the motor’s power-up/reset position is 
set automatically to zero.  In this case, a homing-search move must be used to establish the position 
reference for the motor. 

(If the position sensor is absolute only over one motor revolution or commutation cycle, as with a single-
turn absolute encoder or resolver, and the motor is commutating with Turbo PMAC, use similar variables 
Ixx81 and Ixx91 to establish the absolute phase position, but in this case Ixx10 will be set to 0, and a 
homing-search move will still be required.  The setup for absolute phase position is covered in the 
Commutation section.)  

The absolute position read defined by Ixx10 and Ixx95 will be performed automatically at power-up/reset 
if bit 2 of Ixx80 is set to its default value of 0.  This absolute read can be done subsequently on the $* 
command, whether or not it was done on power-up/reset. 

The sensor used for absolute power-on position does not have to be the same sensor as that used for 
ongoing position feedback, and it does not have to use the same data format or channel.  However, in 
order to use the automatic absolute power-on position read with Ixx10 and Ixx95, it must have the same 
resolution as the ongoing position feedback.  If the absolute power-on position has a different resolution, 
you must write directly to the motor’s absolute position feedback register (suggested M-variable Mxx62), 
usually from a power-on PLC program.  If the absolute position sensor for Motor 1 has 0.4 counts per 
count of the ongoing position feedback and this sensor were read through M150, the power-on PLC 
statement to set the absolute position could be: 

M162=M150*0.4*I108*32 

This must be done with the motor’s loop open.  Typically, power-up mode variable Ixx80 (see just below) 
will be set to 0 or 2 and the loop will be closed after this statement is executed. 

Ixx80 specifies whether PMAC will try to control the motor immediately on power-up/reset (bit 0 = 1), 
performing a phasing search if necessary; or whether it will put the motor in a killed state on power-
up/reset (bit 0 = 0) and await a command to enable the motor.  If not sure that everything is instantly 
ready for control when Turbo PMAC is powered up, set bit 0 of Ixx80 to 0 (making Ixx80 an even 
number).  In general, the more complex and high-powered the system is, the more likely to delay enabling 
of the motor to ensure that everything is ready before attempting to enable the motor. 

Ixx80 also controls what kind of phasing-search move is done if one is required for a PMAC-commutated 
motor (this is covered in the Commutation section), and whether an absolute position read is done 
automatically on power-up/reset.