Properties And Parameterization Of The Modbus Tcp Server - Siemens SICAM Q100 System Manual

Exception Code 03 ILLEGAL_DATA_VALUE
• The redundancy client addresses a register that does not allow access to partial data. The register has a
complex data structure and is distributed across several registers. The register can be read or written only
as a whole.
• The Modbus client tries to write to the Modbus server for which the access rights are set to "read only".
Exception Code 04 SERVER_FAILURE
• Error during the time format conversion in the Modbus server because a faulty date/time format was re-
ceived via Modbus, for example month format > 12.
2.2.3

Properties and Parameterization of the Modbus TCP Server

Properties of the Modbus TCP Server
• 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.
• 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.
• Communication sequence:

The client sends a request to the server to start a data transmission from the server to the client.

If the requested data are not available, the server sends an error feedback to the client.
• The Modbus TCP data packet has a maximum size of 260 bytes:

253 bytes max. for data and

7 bytes for the Modbus TCP header
Parameterization
The following parameters can be set for the Modbus TCP bus protocol (see also Device Manual SICAM Q100,
chapter 8):
Table 2-2
Parameter
IP address
Subnet mask
Default gateway
Ethernet switch on
Enable SNMP
SICAM Q100, 7KG95xx, System Manual
E50417-C1040-C522-A8, Edition 09.2020
Modbus TCP Settings
Default Setting
192.168.0.55
255.255.255.0
192.168.0.1
no
no
Settings
any,
0.0.0.0 for DHCP
any
any
no
yes
no
yes
Communication
2.2 Modbus
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