User's Manual

PMAC User Manual
Writing Programs for PMAC 167
Note:
If PMAC is operating in move segmentation mode (I13>0), which is required for
circular interpolation, this Ix17 acceleration limit is not observed.
Do not set both the TA and TS (Ix87 and Ix88.) times to zero, even if planning to
rely on the acceleration limit. This would cause a divide-by-zero error, yielding
possible erratic performance.
When not Effective Enough
PMAC looks two moves ahead of actual move execution to perform its acceleration limit, and can
recalculate these two moves to keep the accelerations under the Ix17 limit. However, there are cases
where more than two moves, some much more than two, would have to be recalculated in order to keep
the accelerations under the limit. In these cases, PMAC will limit the accelerations as much as it can, but
because the earlier moves have already been executed, they cannot be undone, and therefore the
acceleration limit will be exceeded.
V
T
Ix87 < 2 * Ix88
2*Ix88
Ix88 Ix88
2*Ix88
Ix88 Ix88
V
T
Ix87 > 2 * Ix88
Ix87
Ix88 Ix88
Ix87
Ix88 Ix88
Ix87 DEFAULT ACCELERATION TIME (PROGRAM)
(Units: msec); integer
Overridden by TA in program
Ix88 DEFAULT S-CURVE TIME (PROGRAM)
(Units: msec); integer
Overridden by TS in program
V
T
Ix88=0
Ix88 Ix88
Figure 26 Coordinate System Variables