Siemens SINUMERIK 840D sl Function Manual page 678

Measurement (M5)
8.5 Axial measurement (optional)
● Measurement memory: Number of FIFO
● Trigger event:
The axial measured values are available in the machine coordinate system (MCS). They are
written to a FIFO variable defined by the user, e.g., $AC_FIFO1. When two probes have
been projected for the measurement, the measured values of the second probe are saved
separately in the subsequent FIFO.
The number of measured values is limited by the following machine data:
MD28264 LEN_AC_FIFO
Variables $AC_MEA and $AA_MM are therefore irrelevant.
The values can be read from the FIFO both in the part program and from synchronized
actions.
The measurement is active until
● MEAC["axis"]=(0) is programmed
● a FIFO is full
● RESET is pressed or end of program M02/M30 is detected
Endless measuring
In order to implement endless measuring, FIFO values must be read cyclically from the part
program. The frequency with which the measured values are read from the FIFO memory
and processed must correspond to the writing frequency of the NC.
The number of valid entries is readable in a FIFO variable.
In order to achieve a defined number of measured values, the measurement function must
be explicitly deselected by the program.
FIFO variables
For definitions of FIFO variables, see
References:
/FB2/ Function Manual, Extended Functions; Synchronized Actions (S5)
678
– Decade (= encoder selection)
0/not set = use active measuring system
1 = 1st measuring system
2 = 2nd measuring system
(if available, otherwise the first measuring system is used; no alarm is generated)
3 = 1st and 2nd measuring system
If two measuring systems are used to take the measurement, a maximum of two trigger
events may be programmed.
1 = rising edge of probe 1
-1 = falling edge of probe 1
2 = rising edge of probe 2
-2 = falling edge of probe 2
Function Manual, 01/2008, 6FC5397-1BP10-3BA0
Extended Functions