User`s manual

98
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
• The following format is used for message data communications.
• Message data consists of a Slave address, function code, communica-
tions data, and error check block.
Message Interval
• 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.
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.
Note In the above communications, the default is –1 (65535) and the LSB (least-
significant 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.
Message data
(DSR message
and response)
Slave address
1 byte
Function code
1 byte
Communications data Error check block
2 bytes
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
Data name Description
Slave address 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).
Function code A command giving instructions of the details of processing to the Inverter.
Example: Data read (03 Hex) and data write (10 Hex)
Communications data Data attached to the command.
Example: The register number of read start data and the number of registers of read
data
Error check CRC-16 check code for checking the reliability of the message data.