Modbus Tcp - Siemens 7XV5673 Device Manual

8.2.3

Modbus TCP

Properties of the Modbus TCP
• Connection-oriented Ethernet protocol based on TCP/IP
• Use of IP addresses for addressing individual components connected to the bus (bus nodes)
• The Modbus TCP protocol has the TCP port number 502 reserved on the server side. It is possible to use
a parameterized port number (see Table 8-2).
• All data types in the Modbus TCP messages which are larger than 1 byte, are stored in the Big-Endian
format, that is the most significant byte (MSB) is stored at the lowest register address and is transmitted
first.
• Sequence of the communication:
−
In order to start data transfer from server to client, the client sends a request to the server.
−
If the requested data is not available, the server sends the client the requested data or an error
feedback.
• The Modbus TCP data packet has a maximum size of 260 bytes:
−
253 bytes max. for data
−
7 bytes for the Modbus TCP header
Parameterization
The following parameters can be set for the Modbus see also chapter 6.3.3.6:
Table 8-2
IP address
Subnet mask
Default gateway
Bus protocol
Use a user-port number
User-port number
(only, if Use a user-port number yes has been
parameterized)
Access rights for user port 502
Access rights for user port
(only, if Use a user-port number yes has been
parameterized)
Keep Alive time
Communication supervision time
SICAM I/O Unit, 7XV5673, Device Manual
E50417-H1040-C484-A3, Edition 05.2012
Modbus TCP Settings
Parameter Default Setting
192.168.0.55
255.255.255.0
192.168.0.1
Modbus TCP
no
10000
Full
Full
10 s
600 * 100 ms
8 Communication
8.2 Modbus
Settings
Any,
0.0.0.0 for DHCP
Any
Any
-
no
yes
10000 to 65535
Full
Read only
Full
Read only
0 s = switch off
1 s to 65 535 s
0 s = none
100 ms to 6 553 400 ms
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