Reference Manual

PMAC 2 Software Reference
PMAC On-Line Command Specification 187
< {Option 6L firmware only}
Function
Back-up through Lookahead Buffer
Scope
Coordinate-system specific
Syntax
<
Remarks
This command causes the PMAC to start reverse execution in the lookahead buffer for the
addressed coordinate system. If the program is currently executing in the forward direction, it
will be brought to a quick stop (the equivalent of the \ command) first.
Execution proceeds backward through points buffered in the lookahead buffer, observing
velocity and acceleration constraints just as in the forward direction. This execution continues
until one of the following occurs:
• Reverse execution reaches the beginning of the lookahead buffer – the oldest stored point
still remaining in the lookahead buffer – and it comes to a controlled stop at this point,
observing acceleration limits in decelerating to a stop.
• The \ quick-stop command is given, which causes PMAC to come to the quickest possible
stop in the lookahead buffer.
• The > resume-forward, R run, or S step command is given, which causes PMAC to resume
normal forward execution of the program, adding to the lookahead buffer as necessary.
• An error condition occurs, or a non-recoverable stopping command is given.
If any motor has been jogged away from the quick-stop point, and not returned with a J=
command, PMAC will reject the < back-up command, reporting ERR017 if I6 is set to 1 or 3.
This same functionality can be obtained from within a PMAC program by setting I1021 to 7,
which executes more quickly than CMD &n<.
If the coordinate system is not currently in the middle of a lookahead sequence, PMAC will
treat this command as an H feed-hold command.
> {Option 6L firmware only}
Function
Resume Forward Execution in Lookahead Buffer
Scope
Coordinate-system specific
Syntax
>
Remarks
This command causes the PMAC to resume forward execution in the lookahead buffer for the
addressed coordinate system. It is typically used to resume normal operation after a \ quick-
stop command, or a < back-up command. If the program is currently executing in the
backward direction, it will be brought to a quick stop (the equivalent of the \ command) first.
If previous forward execution had been in continuous mode (started with the R command),
the > command will resume it in continuous mode. If previous forward execution had been
in single-step mode (started with the S command), the > command will resume it in single-
step mode. The R and S commands can also be used to resume forward execution, but they
may change the continuous/single-step mode.
Deceleration from a backward move (if any) and acceleration in the forward direction
observe the Ix17 acceleration limits.
If any motor has been jogged away from the quick-stop point, and not returned with a J=
command, PMAC will reject the > resume command, reporting ERR017 if I6 is set to 1 or 3.
This same functionality can be obtained from within a PMAC program by setting I1021 to 6,
which executes more quickly than CMD &n>.
If the coordinate system is not currently in the middle of a lookahead sequence, PMAC will
treat this command as an R run command.