Reference Manual

Turbo PMAC/PMAC2 Software Reference

Turbo PMAC On-line Command Specification 278

Function: Quick Stop in Lookahead / Feed Hold

Scope: Coordinate-system specific

Syntax: \

This command causes the Turbo PMAC to calculate and execute the quickest stop within the lookahead

buffer for the addressed coordinate system that does not violate acceleration constraints for any motor

within the coordinate system. Motion will continue to a controlled stop along the programmed path, but

the stop will not necessarily be at a programmed point.

The \ quick-stop command is generally the best command to stop motion interactively within lookahead.

Its function is much like that of a traditional feed-hold command, but unlike the regular H feed-hold

command in Turbo PMAC, it is guaranteed to observe constraints.

Note:

The use of DWELL, WHILE({condition})WAIT, and a violation of the double-

jump-back rule momentarily switches PMAC out of lookahead mode. Therefore,

these constructs should not be used in programs and sub-programs when the \

quick-stop command will be used to control their lookahead state.

Once stopped, several options are possible:

 Jog axes away with any of the jogging commands. The on-line jog commands can be used to jog any

of the motors in the coordinate system away from the stopped point. However, before execution of

the programmed path can be resumed, all motors must be returned to the original stopping point with

the J= command.

 Start reverse execution along the path with the < command.

 Resume forward execution with the >, R, or S command.

 End program execution with the A command.

This same functionality can be obtained from within a Turbo PMAC program by setting Isx21 to 4, which

executes more quickly than CMD “&n\”.

If the \ command is given to a coordinate system that is not currently executing moves within the

lookahead buffer, Turbo PMAC will execute the H feed-hold command instead.