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Service Access Point (SAP) and
PROFIBUS Services
Introduction
Audience
Definition
Service Access
Point
Communications Processor CP 541
EWA 4NEB 812 6188-02
You do not necessarily require information on the service access points to
work with the CP 541. You can specify a service access point for broadcast
with parameter BSAP in frame COM of DB1.
The PROFIBUS services used by the CP 541 are given in Table G-2.
This chapter is intended for the bus specialist wanting more detail on the in-
ternal data transmission process on SINEC L2.
A message on SINEC L2 is identified and read in by the intended receiving
station, by means of the station number carried with the message. To reach its
destination, another parameter, the service access point (SAP) is specified in
the message.
The CP 541 handles the entering of station number and SAP for you. You can
adjust the SAP for broadcast to your bus in DB1.
The intended SAPs in the CP 541 are shown in Table G-1.
Table G-1
Meanings of Service Access Points (SAPs)
SAP
0
If you assign the value 0 to parameter BSAP, this indicates to
the CP 541 that broadcast will not be used. No SAP will be
assigned for broadcast.
*
2 ... 31
PLC-PLC connection
33 ... 52
Broadcast, selectable with BSAP
55 ... 62
DP connection according to DIN E 19245, Part 3
*
The following definitions apply to PLC-PLC connections:
SAP 2 means PLC-PLC connection to station 1
SAP 3 means PLC-PLC connection to station 2, etc. up to
SAP 31 means PLC-PLC connection to station 30
G
Meaning
G-1
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