Reference Manual

Turbo PMAC/PMAC2 Software Reference
Turbo PMAC Global I-Variables 216
This means that I7002, in conjunction with I7001 and I7000, controls the Servo clock frequency for the
entire Turbo PMAC2 system. (For Turbo PMAC2 Ultralite boards, I6802, I6801 and I6800 control this.)
Each cycle of the Servo clock, Turbo PMAC2 updates the commanded position for each activated motor,
and executes the servo algorithm to compute the command to the amplifier or the commutation algorithm.
Specifically, I7m02 controls how many times the Servo clock frequency is divided down from the Phase
clock, whose frequency is set by I7m01 and I7m00. The Servo clock frequency is equal to the Phase
clock frequency divided by (I7m02+1). I7m02 has a range of 0 to 15, so the frequency division can be by
a factor of 1 to 16. The equation for I7m02 is:
1
)kHz(ServoFreq
)kHz(PhaseFreq
02m7I 
The ratio of Phase Clock frequency to Servo Clock frequency must be an integer.
For execution of trajectories at the proper speed, I10 must be set properly to tell the trajectory generation
software what the Servo clock cycle time is. The formula for I10 is:
)kHz(ServoFreq
608,388,8
10I 
In terms of the variables that determine the Servo clock frequency on a (non-Ultralite) Turbo PMAC2
board, the formula for I10 is:
   
17002I17001I37000I*2
9
640
10I 
At the default servo clock frequency, I10 should be set to 3,713,992 in order that Turbo PMAC2’s
interpolation routines use the proper servo update time.
Note:
If the servo clock frequency is set too high, lower priority tasks such as
communications can be starved for time. If the background tasks are completely
starved, the watchdog timer will trip, shutting down the board. If a normal reset of
the board does not re-establish a state where the watchdog timer has not tripped
and communications works well, it will be necessary to re-initialize the board by
powering up with the E3 re-initialization jumper on. This restores default settings,
so communication is possible, and I7000, I7001, and I7002 can be set to
supportable values.
For accessory boards in which alternate addressing of the Servo IC is used (labeled Servo IC m*), this
function is controlled by I7m52, not I7m02.
Example:
With a 6.67 kHz Phase Clock frequency established by I7000 and I7001, and a desired 3.33 kHz Servo
Clock frequency:
I7002 = (6.67 / 3.33) - 1 = 2 - 1 = 1
See Also: I10, I19, I7m00, I7m01, I7m07, I6800, I6801, I6802, I6807