Eaton M-Max Series User Manual page 156

Serial Interface (Modbus RTU)
Explanation of Function Code
Function Code 03 (hex): Reading of Holding Registers
This function reads the content of a number of consecutive
holding registers (of specified register addresses).
Example:
Reading of motor speed (ID 2105) and motor current (ID
2106) of the M-Max frequency inverter with the slave
address 5.
Master request: 05 03 0838 0002 4622 (hex)
Hex Name
05 Slave address
03 Function code (reading of holding registers)
0838 2104 (dec): The ID number of the first requested
register is 2105 (dec) as the master PLC has an
offset of +1.
0002 Total number of requested registers
(42105–42106)
4622 CRC
Slave response: 05 03 04 05D7 0018 0F0D (hex)
Hex Name
05 Slave address
03 Function code (reading of holding registers)
04 Number of consecutive data bytes
(2 registers x 2 bytes = 4 bytes)
05D7 Content (2 bytes) of register 42105: 1495 (dec)
(motor speed = 1495 RPM)
0018 Content (2 bytes) of register 42106: 0024 (dec)
(motor current = 0.24A)
0F0D CRC
140 M-Max Series Adjustable Frequency Drive MN04020003E—October 2013 www.eaton.com
Function Code 04 (hex): Reading of Input Registers
This function reads the content of a number of consecutive
input registers (of specified register addresses).
Example:
Reading of motor speed (ID 2105) and motor current (ID
2106) of the M-Max frequency inverter with the slave
address 5.
Master request: 05 04 0838 0002 F3E2 (hex)
Hex Name
05 Slave address
04 Function code (here: Reading of input registers)
0838 2104 (dec): The ID number of the first requested
register is 2105 (dec) as the master PLC has an
offset of +1.
0002 Total number of requested registers
(32105–32106)
F3E2 CRC
Slave response: 05 04 04 05D7 0018 0EBA (hex)
Hex Name
05 Slave address
04 Function code (here: Reading of input registers)
04 Number of consecutive data bytes
(2 registers x 2 bytes = 4 bytes)
05D7 Content (2 bytes) of register 32105: 1495 (dec)
(motor speed = 1495 RPM)
0018 Content (2 bytes) of registers 32106: 0024 (dec)
(motor current = 0.24A)
0EBA CRC