Rockwell Automation Publication MOTION-RM002H-EN-P-February 2018 201
Execution Schedule
Control over the MATC instruction’s execution schedule is via the Execution
Schedule parameter.
Note that for the Master Driven Speed Control (MDSC) function, the Execution
Schedule equal pending is used in both Master Driven Mode and Time Driven
Mode.
Immediate Execution
By default, the MATC instruction is scheduled to execute immediately by virtue
of the fact that the default setting of the Execution Schedule parameter is
Immediate. In this case, there is no delay to the enabling of the time camming
process.
As illustrated in the diagram below, when the MATC instruction is executed, the
camming process is initiated on the specified axis and the Time Cam Status bit in
the axis’ Motion Status word is set. If the Execution Schedule parameter is set to
Immediate, the axis is immediately locked to the time master coordinate according
to the specified Cam Profile.
If an MATC instruction is executed on an axis that is already actively time
camming, an Illegal Dynamic Change error is generated (error code 23). The only
exception for this is if the Execution Schedule is specified as pending.
Pending Cam Execution
Alternatively, the MATC instruction’s execution can, in effect, be deferred
pending completion of a currently executing time cam. An Execution Schedule
selection of Pending can thus be used to seamlessly blend two time cam profiles
together without stopping motion.
The Pending execution feature is particularly useful in applications when the axis
must be accelerated up to speed using a specific velocity profile. When this
acceleration profile is done, it must be smoothly blended into a cam profile which
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