Reference Manual

Turbo PMAC/PMAC2 Software Reference
Turbo PMAC Global I-Variables 96
If this target position is calculated within the special lookahead buffer, when this position is greater in an
absolute sense (not magnitude) than [Ixx13-Ixx41], Turbo PMAC modifies this position to [Ixx13-Ixx41].
Depending on the setting of bit 14 of Ixx24, it either brings the program to a controlled stop at this point
(bit 14=0) or continues the program with the motor position saturated to this value (bit 14=1).
If stopped at the limit in lookahead, reversal along the path is possible. Commands for forward execution
into the limit will execute one segment at a time in a point-to-point fashion. If the software limit is
extended, normal program execution may be resumed. Because program execution is technically only
suspended when stopped at the limit in this mode, an Abort command must be issued before another
program can be run.
Lookahead is active for LINEAR and CIRCLE mode moves, provided that the lookahead buffer is
defined, and with Isx13 and Isx20 set to values greater than 0.
If Ixx13 is set to 0, there is no positive software limit (if 0 should be the limit, use 1). This limit is
automatically de-activated during homing-search moves, until the home trigger is found. It is active
during the post-trigger move.
Ixx13 is referenced to the most recent power-up zero position or homing-move zero position. The
physical position at which this limit occurs is not affected by axis-offset commands (e.g. PSET,
{axis}=), although these commands will change the reported position value at which the limit occurs.
Note:
It is possible to set this parameter outside the range +2
35
(+64 billion) if a couple of
special things are done. First, the Ixx08 scale factor for the motor must be reduced
to give the motor the range to use this position (motor range is +2
42
/Ixx08).
Second, the variable value must be calculated inside Turbo PMAC, because the
command parser cannot accept constants outside the range +2
35
(e.g. to set I113 to
100 billion, use I113=1000000000*100).
Ixx14 Motor xx Negative Software Position Limit
Range: -2
35
- +2
35
Units: counts
Default: 0 (disabled)
Ixx14 sets the maximum permitted positive position value for Motor xx. It can work in two slightly
different ways.
1. Actual position limit: Turbo PMAC’s “housekeeping” functions repeatedly compare the actual
position of Motor xx to Ixx14. If the motor is closed-loop, and the actual position is less in an absolute
sense (not magnitude) than Ixx14, Turbo PMAC issues an Abort command automatically, which causes
this motor to start decelerating to a stop at the rate set by Ixx15. If other motors are in coordinated
motion, they are also brought to a stop at their own Ixx15 rate.
Note:
In this mode, the deceleration starts after the limit has been reached, so the motion
will end outside the limit.
If the motor is in open-loop enabled mode (from an O-command) when it exceeds the Ixx13 limit, it will
be aborted (closed-loop stop). If the limit has already been exceeded, no open-loop commands are
accepted for this motor, regardless of polarity.
While the Ixx14 limit is exceeded, Turbo PMAC will allow no more negative-direction commands,
whether from a programmed move, a jog command, or from the position-following function. However, it
will allow positive-direction commands of any of these types, permitting a controlled exit from the limit.
2. Desired position limit: If bit 15 of Ixx24 is set to 1, enabling desired position limit checking, Turbo
PMAC will compared the desired motor target as calculated by the motion program position – either end