Siemens SINUMERIK 840D sl Programming Manual page 265

Continuous measurement (MEAC)
The measured values for
the programmed FIFO[n] memory (circular buffer). If two probes are configured for the
measurement, the measured values of the second probe are stored separately in the
FIFO[n+1] memory configured especially for this purpose (defined in machine data).
The FIFO memory is a circular buffer in which measured values are written to $AC_FIFO
variables according to the circular principle, see Section "Synchronized actions (Page 553)".
Note
FIFO contents can be read only once from the circulating storage. If this measured data is to
be used several times, it must be buffered in the user data.
If the number of measured values for the FIFO memory exceeds the maximum value defined
in machine data, the measurement is automatically terminated.
An endless measuring process can be implemented by reading out measured values
cyclically. In this case, data must be read out at the same frequency as new measured
values are read in.
References:
● Function Manual, Synchronized Actions; Detailed Description,
● Function Manual, Extended Functions; Measurements (M5), Section: Axial measurement
Protection against programming errors
The following programming errors are detected and indicated appropriately:
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Job Planning
Programming Manual, 03/2013, 6FC5398-2BP40-3BA1
Section: Parameters ($AC_FIFO)
/ programmed with
MEASA MEAWA
Example:
N01 MEAS=1 MEASA[X]=(1,1) G01 F100 POS[X]=100
/ with number of parameters <2 or >5
MEASA MEAWA
Example:
N01 MEAWA[X]=(1) G01 F100 POS[X]=100
/ with trigger event not equal to 1/ -1/ 2/ -2
MEASA MEAWA
Example:
N01 MEASA[B]=(1,1,3) B100
/ with invalid mode
MEASA MEAWA
Example:
N01 MEAWA[B]=(4,1) B100
/ with trigger event programmed twice
MEASA MEAWA
Example:
N01 MEASA[B]=(1,1,-1,2,-1) B100
4.8 Axial measurement (MEASA, MEAWA, MEAC) (option)
are available in the machine coordinate system and stored in
MEAC
/ in the same block
MEAS MEAW
Special motion commands
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