Siemens SIMATIC FM 452 Manual page 137

Listen-In
"Listen-In" means the following: An absolute encoder is operated in parallel on two
modules (for example FM 451 and FM 452). The FM 451 positioning module is
the master and the clocks the absolute encoder, and the FM 452 electronic cam
controller is the slave and listens in to the signals of the SSI frame.
Set "Increments/Encoder Revolution" and "Number of Revolutions" to the master
setting. The transmission rate is irrelevant. Depending on the encoder type select
"Listen-In" or "Listen-In Right-Justified" for "Frame Length".
Wiring Listen-In
Figure 10-3 based on the example of an FM 451 and FM 452 illustrates how to
connect the absolute encoder so that the FM 452 listens in.
15
14
Figure 10-3
Note
If you want the FM 452 to listen in, you must connect the ground (M) of the
encoder power supply of the master (for example FM 451: front connector, pin 48)
and of the slave (FM 452: front connector, Pin 48) making low-resistance
connection with the ground of the CPU.
FM 452 Electronic Cam Controller
C79000-G7076-C452-04
DAT
DAT
CLS
2
CLS
3
Ground
7
+24 V
5
Shield to
housing
DAT
4
DAT
5
CLI
6
CLI
7
Shield to
housing
Connection of Absolute Encoders (SSI)
red
blue
yellow
green
brown
white
pink
gray
Shield to
housing
FM 452 "listens in"
Wires twisted in pairs
Must be connected to
encoder interface of master.
Encoders
10-7