Siemens SINUMERIK 840D sl Programming Manual page 301

Further information
Measurement job
A measuring task can be programmed in the part program or from a synchronized action
(see the chapter titled "Motion-synchronous actions"). Please note that only one measuring
job can be active at any given time for each axis.
Note
The feed must be adjusted to suit the measuring task in hand.
In the case of MEASA and MEAWA, the correctness of results can be only guaranteed for
feedrates at which no more than 1 trigger event of the same type and no more than 4 trigger
events of different types occur in each position controller cycle.
In the case of continuous measurement with MEAC, the ratio between interpolation cycle and
position control cycle must not exceed 8:1.
Trigger event
A trigger event comprises the number of the probe and the trigger criterion (rising or falling
edge) of the measuring signal.
Up to 4 trigger events of the addressed probe can be processed for each measurement; in
other words, up to 2 probes with 2 measuring signal edges each. The processing sequence
and the maximum number of trigger events depend on the selected mode.
Note
The following applies for measuring mode 1: The same trigger event may only be
programmed once in one measuring task.
Operating mode
The first digit (tens decade) of the operating mode selects the required measuring system. If
only one measuring system is installed, but a second programmed, the installed system is
automatically selected.
Job Planning
Programming Manual, 06/2009, 6FC5398-2BP20-0BA0
4.8 Extended measuring function (MEASA, MEAWA, MEAC) (option)
Special motion commands
301