Starting Address Lo
1 byte
Quantity of Registers Hi
1 byte
Quantity of Registers Lo
1 byte
CRC
2 bytes
Example: Set baud rate to 115200 baud (address 529)
Query: 1,16,2,17,0,1,2,0,5,70,210
Slave address = 1 (0x01)
Function = 16 (0x10)
Starting Address Hi, Lo = 2, 17 (0x02,0x11)
Quantity of Registers Hi, Lo = 0, 1 (0x00,0x01)
Byte Count = 2 (0x02)
Registers Value Hi, Lo = 0, 5 (0x00,0x05)
CRC = 70,10 (0x46, 0x0A)
Starting address 0x0211 = 529
Number of registers = 0x0001 = 1
Data 0x0005 = (115200 = value 5)
Response: 1,16,2,17,0,1,80,116
Slave address = 1 (0x01)
Function = 16 (0x10)
Starting Address Hi, Lo = 2, 17 (0x02,0x11)
Quantity of Registers Hi, Lo = 0, 1 (0x00,0x01)
CRC = 80,116 (0x50, 0x74)
Function code 8 (Diagnostics)
Modbus function code 8 provides a series of tests for checking the communication system
between a client (Master) device and a server (Slave).
The following diagnostics functions are supported:
Sub-
func‐
tion
code
(Dec)
Name
Description
00
Return Query Data
The data passed in the request data field is to be returned
(looped back) in the response.
10
Clear Counters and Diagnostic
Register
Clears all counters and the diagnostic register. Counters are
also cleared upon power–up.
11
Return Bus Message Count
The response data field returns the quantity of messages that
the remote device has detected on the communications sys‐
tem since its last restart, clear counters execution, or power–
up.
12
Return Bus Communication Er‐
ror Count
The response data field returns the quantity of CRC errors en‐
countered by the remote device since its last restart, clear
counters execution, or power–up.
Modbus communication FCT010
C.2 Modbus function codes
SITRANS MASS 2100 & FC300 (FCT010/DSL)
154
Operating Instructions, 06/2020, A5E39788682-AB