Mitsubishi Electric FR-A700 Technical Manual page 428

Message field
1) ADDRESS field
2) FUNCTION field
3) DATA field
4) CRC CHECK field
(5) Message format types
The message formats corresponding to the function
codes in Table 1 above will be explained.
Read holding register data (H03 or 03)
Can read the description of 1) system environment
variables, 2) real-time monitor, 3) faults history, and
Query message
1) Slave
Address
(8bit)
Normal response (Response message)
1) Slave
Address
(8bit)
•Query message setting
Message
1) Slave Address
2) Function
3) Starting
Address
4) No. of Points
The address code is 1 byte long (8 bits) and any of 0 to 247 can be set. Set 0 to send a broadcast message
(all-address instruction) or any of 1 to 247 to send a message to each slave.
When the slave responds, it returns the address set from the master.
The value set to [Pr. 117, 331 ] is the slave address.
The function code is 1 byte long (8 bits) and any of 1 to 255 can be set. The master sets the function that it
wants to request to the slave, and the slave performs the requested operation. The following table gives the
supported function codes. An error response is returned if the set function code is other than those in the
following table.
When the slave returns a normal response, it returns the function code set by the master. When the slave
returns an error response, it returns H80 + function code.
Code Function Name
H03 Read Holding Register
H06 Preset Single Register
H08 Diagnostics
H10 Preset multiple registers
Read Holding Register
H46
Access Log
The format changes depending on the function code. Data includes the byte count, number of bytes,
description of access to the holding register, etc.
The received message frame is checked for error. CRC check is performed, and 2byte long data is added to
the end of the message. When CRC is added to the message, the low-order byte is added first and is
followed by the high-order byte.
The CRC value is calculated by the sending side that adds CRC to the message. The receiving side
recalculates CRC during message receiving, and compares the result of that calculation and the actual
value received in the CRC CHECK field. If these two values do not match, the result is defined as error.
3) Starting
2) Function
Address
H03 H
(8bit) (8bit)
5) Byte
2) Function
Count
H03
(8bit)
(8bit)
Set the address to which a message will be sent. Broadcast communication cannot be made (0 is invalid).
Set H03.
Set the address at which holding register data read will be started.
Starting address = Starting register address (decimal) - 40001
For example, setting of the starting address 0001 reads the data of the holding register 40002.
Number of holding registers from which data will be read. The number of registers from which data can be
read is a maximum of 125.
Description
Description
Reads the holding register data.
Writes data to the holding
register.
Makes a function diagnosis.
(communication check only)
Writes data to multiple
consecutive holding registers.
Reads the number of registers
that succeeded in communication
last time.
Table 1: Function code list
4) inverter parameters assigned to the holding
register area (refer to the register list (page 468)).
4) No. of Points
L H L
(8bit) (8bit) (8bit)
6) Data
H L
(8bit) (8bit)
Setting Description
462
PARAMETER
Broadcast
Communication
Disabled
Enabled
Disabled
Enabled
Disabled
CRC Check
L H
(8bit) (8bit)
CRC Check
...
L
(8bit)
(n 16bit)
H
(8bit)