Data; Function Code; Error Check; Header And Trailer - Omron 3G3MX2 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

01h Read Coil Status
03h Read Holding Register
05h Write in Coil
06h Write in Holding Register
08h Loopback Test
0Fh Write in Coils
10h 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
299