Siemens SINUMERIK 840D sl Programming Manual page 620

Work preparation
3.7 Special motion commands
If the measuring operation is performed with two measuring systems, a maximum of two trigger
events can be programmed (positive or negative edge). The measured values of both probes
are acquired for both of the trigger events.
With the use of PROFIBUS telegram 391 (default setting for PROFIBUS communication) only
one measured value is possible for each trigger event and position control cycle.
When using PROFIBUS telegram 395, for MEAC in operating mode 1, the number of measured
values for each trigger event can be increased to a total of 8 measured values for increasing
and 8 for falling edge per trigger event and position controller clock cycle:
● One probe: 8 measured values for a positive and 8 for a negative edge
● Two probes: 4 measured values for a positive and 4 for a negative edge for each probe
This means that higher feed rates or higher speeds can be reached by using PROFIBUS
telegram 395.
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 is programmed, the installed system is
automatically selected.
The second digit (units decade) selects the desired measuring mode. The measuring process
is thus adapted to the options supported by the relevant control:
● Mode 1
Trigger events are evaluated in the chronological sequence in which they occur.
● Mode 2
Trigger events are evaluated in the programmed sequence.
● Mode 3
Trigger events are evaluated in the programmed sequence but there is no monitoring of
trigger event 1 at the start.
Measurement with and without delete distance-to-go
When command MEASA is programmed, the distance-to-go is not deleted until all required
measured values have been acquired.
MEAWA is used for special measuring tasks in which a programmed position always has to be
approached.
Note
MEASA cannot be programmed in synchronized actions. As an alternative, MEAWA plus
delete distance-to-go can be programmed as a synchronized action.
If the measuring job with MEAWA is started from synchronized actions, the measured values
will only be available in the machine coordinate system.
Geometry axes/transformations
If axial measurement is to be started for a geometry axis, the same measuring job must be
programmed explicitly for all remaining geometry axes. The same applies to axes involved in
a transformation.
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Programming Manual, 12/2019, 6FC5398-2EP40-0BA0
NC programming