Reference Manual

PMAC 2 Software Reference
PMAC I-Variable Specification 155
Note:
On PMAC2 boards that are not “Ultralite”, I997 does not control
the Phase Clock frequency; I901 does. I997 has no effect on non-
Ultralite versions of the PMAC2.
Specifically, I997 controls how many times the PHASE clock frequency is divided down
from the maximum phase clock, whose frequency is set by I992. The PHASE clock
frequency is equal to the maximum phase clock frequency divided by (I997+1). I997 has a
range of 0 to 15, so the frequency division can be by a factor of 1 to 16. The equation for
I997 is:
1
)kHz(PhaseFreq
)kHz(eqMaxPhaseFr
997I −=
The ratio of MaxPhase Freq. to PHASE Clock Freq. must be an integer.
Note:
If jumper E1 is ON, PMAC2 Ultralite gets its PHASE clock signal
externally from a serial-port input, and I997 is not used.
Note:
If the phase 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 I992
and I997 can be set to supportable values.
Example
With a 20 kHz MaxPhase Clock frequency established by I992, and a desired 6.67 kHz
PHASE clock frequency, the ratio between MaxPhase and PHASE is 3:
I997 = (20 / 6.67) - 1 = 3 -1 = 2
I998 Servo Clock Frequency Control {PMAC2 only}
Range
0 .. 15
Units
Servo Clock Frequency = PHASE Clock Frequency / (I998+1)
Default
3
SERVOClock Frequency = 9.0346 kHz / (3+1) = 2.2587 kHz
(with default values of I992 and I997)
Remarks
I998, in conjunction with I997 and I992, determines the frequency of the SERVO clock on
PMAC2 Ultralite. Each cycle of the SERVO clock, PMAC2 Ultralite updates the
commanded position for each activated motor, and executes the servo algorithm to
compute the command output to the amplifier.
Note:
On PMAC2 boards that are not “Ultralite”, I998 does not control
the Servo Clock frequency; I902 does. I998 has no effect on non-
Ultralite versions of the PMAC2.