Message Communications Basic Format
Chapter 7-3
7-3 Message Communications Basic Format
The following description provides information on the format of message data
(DSR and response data).
Message communications of the Inverter conform to the MODBUS
Communications Protocol, which does not require message start and end processing.
(The MODBUS Communications Protocol is a trademark of AEG Schneider
Automation.)
Communications Format
Message data
(DSR message and response)
Slave address
1 byte
Message Interval
• The following format is used for message data communications.
• Message data consists of a Slave address, function code, communications data, and error check block.
Function code
1 byte
Communications data Error check block
2 bytes
• When the Inverter receives a DSR message from the Master, the Inverter waits for a period that is equivalent to 24 bits in length and a Send Wait
Time set in n73. Then the Inverter will return a response. Set n73 according to the Master’s processing time or the timing adjustment.
• When the Master issues the next message after receiving the response from the Inverter, the Master must wait for a 24-bit period plus another period of at least 10 ms.
DSR message from Master Response from Inverter DSR message from Master
24-bit (or 3-byte) standby period
Standby period set in n73
24-bit (3-byte) standby period
Set a standby period of 10 ms or more for the Master
Message Data Configuration
• The communications message is configured entirely of hexadecimal data.
(ASCII and FINS are not used.)
• Communications data is divided into the four areas shown in the following table.
Data name
Slave address
Function code
Communications data
Error check
Description
Set the Slave address (the set value in n70) of the Inverter, to which the DSR message is sent. The Slave address must be within a range from 00 to 32 (00 to 20 Hex).
A command giving instructions of the details of processing to the Inverter.
Example: Data read (03 Hex) and data write (10 Hex)
Data attached to the command.
Example: The register number of read start data and the number of registers of read data
CRC-16 check code for checking the reliability of the message data.
Note In the above communications, the default is –1 (65535) and the LSB (leastsignificant byte) is converted as MSB (most-significant byte) (in the opposite direction). The CRC-16 check is automatically performed by using the protocol macro function of OMRON’s SYSMAC CS/CJ-series, C200HX/HG/
HE, or CQM1H Programmable Controllers.
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Message Communications Basic Format
Chapter 7-3
Slave Address
Note
• The Master can communicate with a maximum of 32 Slaves over RS-
422A/485. A unique Slave address is allocated to each Slave (Inverter) for communications.
• Slave addresses are within a range from 00 to 32 (00 through 20 Hex). If a
DSR message is issued to Slave address 00, the message will be a broadcast message.
The broadcast message is addressed to all Slaves. Only the RUN command
(register 0001 Hex) and frequency command (register 0002 Hex) can be written to the message. The Inverter receiving this message does not return a response regardless of whether or not the message is received properly.
Therefore, for measures against communications errors, the monitor function of the Inverter should be used for checking the reception of broadcast messages.
Function Code
• The function code is a command giving instructions of the details of processing to the Inverter.
• The following three functions codes are available.
#
Function code
03 Hex
08 Hex
10 Hex
Command name
Data read
Loop-back test
Data write
Note
Description
Reads the data of the specified register number. Consecutive data of a maximum of 16 words (32 bytes) can be read.
The DSR message is returned as a response. This command is used for checking the status of communications.
The attached data in the format is written to the specified register number. Consecutive data of a maximum of 16 words (32 bytes) can be written.
1.
Do not use any code other than the above, otherwise the Inverter will detect a communications error and return an error message.
2.
The Inverter uses the same function code for the response. If an error occurs, however, the MSB of the function code will be set to 1. For example, if an error occurs in a DSR message with function code 03, the function code of the response will be 83.
Communications Data
Communications data is attached to the command. The contents and its arrangement of communications data vary with the function code. For details,
refer to 7-4 DSR Message and Response
.
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Message Communications Basic Format
Error Check
Chapter 7-3
The CRC-16 check code is the remainder (16 bits) when all of the message blocks from the Slave address to the final communications data are connected in series, as shown in the following diagram, and this data is divided by a fixed 17-digit binary number (1 1000 0000 0000 0101).
8 bits
The LSB of the Slave address is handled as the MSB in CRC-16 calculation.
Slave address
Function code
Start of communications data
End of communications data
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