Rockwell Automation Publication MOTION-RM002H-EN-P-February 2018 145
offending axis to access the Axis Properties screen. Go to the Dynamics tab and
make the appropriate change to the Maximum Deceleration Value. If the
Extended Error number is -1, this means the Coordinate System has a Maximum
Deceleration Value of 0. Go to the Coordinate System Properties Dynamics Tab
to correct the Maximum Deceleration value.
MCD Changes to Status Bits
For the Master Driven Speed Control (MDSC) function, when the MCD is
executed (goes IP), the status bit (CalculatedDataAvailable (CDA)) is cleared in
an MAM instruction, which indicates that the Event Distances has been
computed. After the MCD is complete and the Event Distances have been
recomputed, the CalculatedDataAvailable status bit is set again. Therefore, look at
the CalculatedDataAvailable status bit after the MCD instruction has been
completed to determine when to use the recomputed Event Distances.
If a MCD is executed, the CDA bit is cleared. The Calculated Data for the move is
recomputed using the new dynamics parameters. The CDA bit is set again when
computations are complete. The Calculated Data that is recomputed is measured
from the original Motion Start Point (MSP) to the Event Distance point using the
new dynamics parameters as changed by the MCD instruction - not from the
point of the MCD.
Note that if the MCD changes the speed to 0, the Event Distance is not
recomputed; the CDA bit is not set. The Event Distance is however recomputed if
a second MCD is issued to restart the motion. The recomputed Calculated Data
includes the duration of the stopped motion.
If the Event Distance is set to 0, the Calculated Data is set to equal the position
that equals the length of the move. This may be one or two coarse update periods
before the PC bit is set because of an internal delay. The end position is typically
achieved in the middle of a coarse update period, which adds up to one additional
coarse update period to the delay. Therefore, if the master is moved a distance
equal to the Calculated Data, you must wait up to 2 iterations more for the PC bit
of the slave move to be set.
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