Communication
2.2 Modbus
19SICAM Q100, 7KG95xx, System Manual
E50417-C1040-C522-A8, Edition 09.2020
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 Modbus TCP Settings
Parameter Default Setting Settings
IP address
192.168.0.55 any,
0.0.0.0 for DHCP
Subnet mask
255.255.255.0 any
Default gateway
192.168.0.1 any
Ethernet switch on no
no
yes
Enable SNMP no
no
yes
SYS_SICAM_Q100_US.book Page 19 Thursday, September 24, 2020 1:17 PM
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