Function Code; Error Check; Header And Trailer (Silent Interval) - Omron MX2 User Manual

Network Protocol Reference
Name of Data
Coil Binary data that can be referenced and changed (1 bit long)
Holding Register 16-bit data that can be referenced and changed

Function Code

0 1 h Read Coil Status
0 3 h Read Holding Resistor
0 5 h Write in Coil
0 6 h Write in Holding Register
0 8 h Loopback Test
0 F h Write in Coils
1 0 h Write in Registers
17h Read/Write Holding Registor
Data:
• A function command is set here.
• The data format used in the MX2 series is corresponding to the Modbus
data format below.
Function code:
Specify a function you want to make the inverter execute. Function codes
available to the MX2 series are listed below.
Function
4
32
2
2
–
4
32
32

Error check:

Modbus-RTU uses CRC (Cyclic Redundancy Check) for error checking.
• The CRC code is 16-bit data that is generated for 8-bit blocks of arbitrary
length.
• The CRC code is generated by a generator polynomial CRC-16 (X16+
X15+ X2+ 1).

Header and trailer (silent interval):

Latency is the time between the reception of a query from the master and
transmission of a response from the inverter.
• 3.5 characters (24 bits) are always required for latency time. If the latency
time shorter than 3.5 characters, the inverter returns no response.
• The actual transmission latency time is the sum of silent interval
(3.5 characters long) + C078 (transmission latency time).
Description
Maximum data size
(bytes available per elements available per message
message)
32 coils (in bits)
16 registers (in bytes)
1 coil (in bits)
1 register (in bytes)
32 coils (in bits)
16 registers (in bytes)
16 registers (in bytes)
Section B-3
Maximum number of data
–
265