Omron RX Series - Page 483

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8 Communications Functions
High-function General-purpose Inverter 3G3RX-V1 User’s Manual (I578-E1)
8-2 Modbus Method
8
The format of a query frame (command) is as follows.
<Slave Address>
• A serial number from 1 to 32 preset for each inverter (slave). Only the inverter that matches the slave
address specified in the query will capture that query.
• Set the slave address to 0 to perform broadcasting (distributing a query to all slave addresses at a
time).
• During a broadcast, you cannot perform data call or loop-back operation.
<Function Code>
• This specifies the function to be performed by the inverter.
• The 3G3RX-V1 Series Inverter supports the following function codes.
Function Code
<Data>
• This sends the function command.
• The data format differs depending on the function code.
• The 3G3RX-V1 Series supports the following data formats used in Modbus communication.
<Error Check>
• In Modbus communication, CRC (Cyclic Redundancy Check) is used for error checking.
• The CRC code is 16-bit data generated for any data block with a data length in 8-bit unit.
• For CRC code generation, the following generator polynomial is used: CRC-16 (X
16
+ X
15
+ X
2
+ 1).
Query Frame Configuration
Header (Silent interval)
Slave address
Function code
Data
Error check
Trailer (Silent interval)
Function code Function
Maximum number of
data bytes per message
Maximum number of
coils/registers per message
01 hex Read coil status 4 32 coils (in bits)
03 hex Read from holding register 8 4 registers (in bytes)
05 hex Write to coil 2 1 coil (in bits)
06 hex Write to holding register 2 1 register (in bytes)
08 hex Loop-back test – –
0F hex Write to multiple coils 4 32 coils (in bits)
10 hex Write to multiple registers 8 4 registers (in bytes)
Data name Description
Coil Binary data (1 bit) that can be referenced or changed.
Holding register 16-bit data that can be referenced to or changed.