2-4
Communications Processor CP 541
EWA 4NEB 812 6188-02
2.3
Broadcast via FDL Connection
The broadcast serves to transmit messages to all L2 stations which monitor
the SINEC L2 via FDL and the set SAP (service access point), and use the
SDN service.
Each broadcast message can contain up to 64 bytes of data.
The CP 541 converts a broadcast message from the connected programmable
controller to a multicast message on SINEC L2. A service access point (SAP)
is used for this conversion.
SAP
The CP 541 uses the default SAP 52 for broadcast. You can change the
SAP with parameter BSAP in frame COM of DB1.
The SAP number must be identical for all participating stations.
SDN
SDN (send data with no acknowledge) of the PROFIBUS protocol is used
for the broadcast.
You send the broadcast from the connected programmable controller to node
address 31. This node address is converted to station number 127 by the CP
541.
PLC
CP
541
31
SINEC L2
127
Figure 2-3 Address Conversion for Broadcast
You can establish a point-to-point connection to any PROFIBUS station
which can exchange data via FDL (free layer 2). You do this with a broadcast
and use the SAP to specify only one other station in SINEC L2 which can
receive the message.
If only the CP 541 and another station in SINEC L2 use this SAP, you can
utilize this special form of broadcast to establish a connection to any other
non-Siemens device.
Introduction
Message Length
Implementation
Address
Conversion
FDL Connection
Communication Modes