Technical data

communication with the SIMATIC S5 PLC, it is necessary to check and
evaluate the status words of the HDB during the communication.
The basic sequence of communication via S5-S5 links is described in
Chapter 7 .
3.3.1.2 Free Layer 2 Communication with FDL Services
For communication with passive or active and heterogeneous stations on
the SINEC L2 bus, the CP provides a free access to layer 2.
With this type of data transmission, it is valuable to understand the services
of layer 2 of the model.
in data block (DB)
HDB
SEND
ANZW
station
ANR 1
Job active
STATION 1
SDA frame
HDB
RECEIVE
SAP 3
station
address
ANR 101
Job complete with/
STATION 2
without error, data
acceptance successful
ANZW
Acknowledgment
B
U
F
F
E
R
SAP 2
address
PLC
CP
CP
PLC
B
U
F
F
E
R
Data to be
transmitted
in data block (DB)
received
Data to be
Fig. 3.10 Handling an S5-S5 Link
Fundamentals of the Model B8976060/02
Volume 1 3 - 12