PMAC-Lite Hardware Reference
10
E-Point
Descriptions
E3 - E6: Servo Clock Frequency Control
The servo clock (which determines how often the servo loop is closed) is derived from the phase clock
(see E98, E29 - E33) through a “divide-by-N” counter. Jumpers E3 through E6 control this dividing
function.
E3
E4
E5
E6
Servo Clock = Phase
Clock Divided by N
Default & Physical Layout
E3 E4 E5 E6
LOC.: E3 E3 E3 E3
ON
ON
ON
ON
N = Divided by 1
OFF
ON
ON
ON
N = Divided by 2
ON
OFF
ON
ON
N = Divided by 3
OFF
OFF
ON
ON
N = Divided by 4
Only E5 and E6 ON
ON
OFF
ON
ON
N = Divided by 5
OFF
ON
OFF
ON
N = Divided by 6
ON
OFF
OFF
ON
N = Divided by 7
OFF
OFF
OFF
ON
N = Divided by 8
ON
ON
ON
OFF
N = Divided by 9
OFF
ON
ON
OFF
N = Divided by 10
ON
OFF
ON
OFF
N = Divided by 11
OFF
OFF
ON
OFF
N = Divided by 12
ON
ON
OFF
OFF
N = Divided by 13
OFF
ON
OFF
OFF
N = Divided by 14
ON
OFF
OFF
OFF
N = Divided by 15
OFF
OFF
OFF
OFF
N = Divided by 16
Adjust the setting of I-variable I10 to match the servo interrupt cycle time set by E98, E29 -- E33, and E3
-- E6. I10 holds the length of a servo interrupt cycle, scaled so that 8,388,608 equals one millisecond.
Since I10 has a maximum value of 8,388,607, the servo interrupt cycle time should always be less than a
millisecond (unless you want to make your basic unit of time on PMAC something other than a
millisecond). If you wish a servo sample time greater than one millisecond, the sampling may be slowed
in software with variable Ixx60.
Frequency can be checked on J4 pins 21 & 22. It can also be checked from software by typing RX:0 in
the PMAC terminal at 10-second intervals and dividing the difference of successive responses by 10000.
The resulting number is the approximate Servo Clock frequency kHz.
If E40-E43 are not all ON, the phase clock is received from an external source through the J4 serial-port
connector, and the settings of E3 – E6 are not relevant.
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