Siemens SIMATIC S7-200 System Manual page 229

MPI Protocol
MPI allows both master-master and master-slave
communications. See Figure 7-8. To communicate
with an S7-200 CPU, STEP 7--Micro/WIN
establishes a master--slave connection. MPI
protocol does not communicate with an S7-200
CPU operating as a master.
Network devices communicate by means of
separate connections (managed by the MPI
protocol) between any two devices. Communication
between devices is limited to the number of
connections supported by the S7-200 CPU or connections supported by the S7-200 CPU or
EM 277 modules. See Table 7-3 for the number of
connections supported by the S7-200.
For MPI protocol, the S7-300 and S7-400 PLCs use the XGET and XPUT instructions to read and
write data to the S7-200 CPU. For information about these instructions, refer to your S7-300 or
S7-400 programming manual.
PROFIBUS Protocol
The PROFIBUS protocol is designed for high-speed
communications with distributed I/O devices (remote
I/O). 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.
PROFIBUS networks typically have one master and
several slave I/O devices. See Figure 7-9. The
master device is configured to know what types of
I/O slaves are connected and at what addresses.
The master initializes the network and verifies that
the slave devices on the network match the the slave devices on the network match the
configuration. The master continuously writes output
data to the slaves and reads input data from them.
When a DP master configures a slave device successfully, it then owns that slave device. If there
is a second master device on the network, it has very limited access to the slaves owned by the
first master.
TCP/IP Protocol
The S7-200 can support TCP/IP Ethernet communication through the use of an Ethernet (CP
243--1) or Internet (CP 243--1 IT) expansion module. Table 7-4 shows the baud rate and number
of connections supported by these modules.
Table 7-4 Number of Connections for the Ethernet (CP 243- -1) and the Internet (CP 243- -1 IT) Modules
Module
Ethernet (CP 243- -1) Module
Internet (CP 243- -1 IT) Module
Refer to the SIMATIC NET CP 243- -1 Communications Processor for Industrial Ethernet Manual
or the SIMATIC NET CP 243- -1 IT Communications Processor for Industrial Ethernet and
Information Technology Manual for additional information.
Communicating over a Network
Baud Rate
10 to 100 Mbaud 10 to 100 Mbaud
STEP 7- -Micro/WIN:
Master
Figure 7-8 MPI Network
S7-200 (EM 277): Slave
S7-300: Master
Figure 7-9 PROFIBUS Network
Connections
8 general purpose connections
1 STEP 7- -Micro/WIN connection
Chapter 7
S7-200: Slave
S7-300: Master
ET 200: Slave
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