Changing Modbus Communication Settings - Siemens SITRANS F Operating Instructions Manual

Modbus communication
A.3 Changing Modbus communication settings
Sub-function Hi
Sub-function Lo
Data Hi
Data Lo
:
Data Hi
Data Lo
CRC
Example: Read Return Slave Message Count (address 529)
Query: 1,8,0,14,0,0,129,200
Slave address = 1 (0x01)
Function = 8 (0x08)
Sub-function Hi, Lo = 0, 14 (0x00,0x0E)
Data Hi, Lo = 0, 0 (0x00,0x00)
CRC = 129,200 (0x81, 0xC8)
Sub-function 0x000E = 14 = Read Return Slave Message Count
Response: 1,8,0,14,0,97,64,32
Slave address = 1 (0x01)
Function = 8 (0x08)
Sub-function Hi, Lo = 0, 14 (0x00,0x0E)
Data Hi, Lo = 0, 97 (0x00,0x65)
CRC = 64,32 (0x41, 0xE3)
Read Return Slave Message Count = 0x0065 = 97 message received
A.3

Changing Modbus communication settings

Changing communication parameters, for example Baud Rate, Modbus Parity Framing or Bus
Address effects the Modbus communication as follows:
• The new settings have effect only after a reset, either by restarting the device or writing the
value 1 to Modbus address 600 Restart communication.
• The new settings will not have effect until the Modbus driver has responded to any ongoing
Modbus request.
90
NOTICE
Setting addresses in a multidrop network
It is recommended NOT to use the default address in a multi-drop network. When setting
device addresses, make sure that each device has a unique address. Replication of addresses
may cause abnormal behavior of the entire serial bus and make the master unable to
communicate with all slaves on the bus.
1 byte
1 byte
1 byte
1 byte
:
1 byte
1 byte
2 bytes
SITRANS FST020 IP65 (NEMA 4X)
Operating Instructions, 05/2022, A5E41425845-AC