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Chapter 4
(2) Message format
Command message that master device sends messages to slave device is called "query", response message that
slave device sends messages to master device is called "response",
The formats of the query and response frames are described below.
Query
Slave address
Function code
Query data
Error check code (CRC-16)
(i) Slave address (node allocation)
The slave address is a number 1 to 247 that is assigned to the inverter (slave) beforehand. (A query is received by
the inverter having the same slave address as that specified in the query.)
The query with the slave address set to "0" at the master device is broadcasted to all the connected inverters. In
case of broadcast communication, all slaves recieve the message, but do not respond.
With a broadcast query, the master device can neither read inverter data nor perform a loopback test.
Slave address of Modbus specification are 1 to 247. In addition, master device can send message to specified slave
devices when slave address set 250 to 254. (Slave device do not respond. Writing command 05h, 06h, 0Fh and 10h
are available.)
Slave address
(ii) Function code
The function code specifies the function to be executed by the inverter.
The table below lists the function codes supported by the SJ700 series inverter.
Function codes
Function code
01h
Reads the coil status.
03h
Reads registers.
05h
Writes data to a coil.
06h
Writes data to a register.
08h
Performs a loopback test.
0Fh
Writes data to multiple coils.
10h
Writes data to multiple registers.
Writes/Read data to multiple
17h
registers.
(iii) Data
The data contains a functional instruction.
The sending format is different depending on the function code.
The SJ700 series inverter supports the following Modbus data format:
Data name
Coil data
Register data
Sending destination
250 (FAh)
Broadcast communication to slave address 01 to 09.
251 (FBh)
Broadcast communication to slave address 10 to 19.
252 (FCh)
Broadcast communication to slave address 20 to 29.
253 (FDh)
Broadcast communication to slave address 30 to 39.
254 (FEh)
Broadcast communication to slave address 40 to 247.
Function
1-bit binary data that can be referenced and changed
16-bit data that can be referenced and changed
Explanation of Functions
Maximum number of data bytes
in a message
4
8
2
2
-
4
8
32/32
Description
4-130
Response
Slave address for confirmation
Function code for confirmation
Response data
Error check code (CRC-16)
Maximum data count in a
message
32 coils (in units of bit)
16 registers (in units of byte)
1 coil (in units of bit)
1 register (in units of byte)
32 coils (in units of bit)
16 registers (in units of byte)
16 registers (in units of byte)
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