Profibus - Siemens SIMATIC S7 System Manual

8.5

PROFIBUS

The PROFIBUS protocol is designed for high-speed communications with distributed I/O
devices (remote I/O). A PROFIBUS system uses a bus master to poll DP I/O devices
distributed in a multi-drop fashion on an RS485 serial bus.
There are many PROFIBUS devices available from a variety of manufacturers. These
devices range from simple input or output modules to motor controllers and PLCs. A
PROFIBUS DP device is any peripheral device which processes information and sends its
output to the master. The DP device forms a passive station on the network (since it does
not have bus access rights) and can only acknowledge received messages or send
response messages to the master upon request. All PROFIBUS DP devices have the same
priority, and all network communication originates from the master.
A PROFIBUS master forms an "active station" on the network. PROFIBUS DP defines two
classes of masters. A class 1 master (normally a central programmable controller (PLC) or a
PC running special software) handles the normal communication or exchange of data with
the DP devices assigned to it. A class 2 master (usually a configuration device, such as a
laptop or programming console used for commissioning, maintenance, or diagnostics
purposes) is a special device primarily used for commissioning DP devices and for
diagnostic purposes.
PROFIBUS networks typically have one master and several DP I/O devices. (Refer to the
figure below.) You configure the master device to know what types of DP devices are
connected and at what addresses. The master initializes the network and verifies that the
DP devices on the network match the configuration. The master continuously writes output
data to the DP devices and reads input data from them.
When a PROFIBUS DP master configures a DP device successfully, it then owns that
DP device. If there is a second master device on the network, it has very limited access to
the DP devices owned by the first master.
The EM DP01 PROFIBUS DP module connects the S7-200 SMART CPU to a PROFIBUS
network as a DP device. The EM DP01 can be the communications partner of DP V0/V1
masters. You can access the EM DP01 GSD file at Siemens Customer Support.
Note
The CPU models CPU CR20s, CPU CR30s, CPU CR40s, and CPU CR60s do not support
the use of expansion modules or signal boards.
S7-200 SMART
System Manual, V2.3, 07/2017, A5E03822230-AF
Communication
8.5 PROFIBUS
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