Siemens SINUMERIK 840D sl Programming Manual page 198

Special Motion Commands
5.8 Extended measuring function (MEASA, MEAWA, MEAC) (option)
Measuring job status for MEASA, MEAWA
If the probe switching state needs to be evaluated in the program, then the measuring job
status can be interrogated via $AC_MEA[n], with n = number of probe. Once all the trigger
events of probe "n" that are programmed in a block have occurred, this variable switches to
the "1" stage. Its value is otherwise 0.
Note
If measuring is started from synchronized actions, $AC_MEA is not updated. In this case, new
PLC status signals DB(31-48) DBB62 bit 3 or the equivalent variable $AA_MEAACT["Axis"]
must be interrogated.
Meaning:
$AA_MEAACT==1: Measurement active
$AA_MEAACT==0: Measurement not active
References:
/FB2/ Function Manual, Extended Functions; Measurements (M5).
Continuous measurement MEAC
The measured values for MEAC are available in the machine coordinate system and stored in
the programmed FIFO[n] memory (circulating memory). 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 circulating memory in which measured values are written to
$AC_FIFO variables according to the circulation principle, see section "Motion Synchronous
Actions"..
Note
FIFO contents can be read only once from the circulating storage. If these measured data
are to be used multiply, they must be buffered in 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.
5-34
Programming Manual, 03/2006 Edition, 6FC5398-2BP10-1BA0
Job planning