Mitsubishi Electric FR-F820-00046, Instruction Manual

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Ethernet communication (FR-F800-E) Parameters
5 - 596
Read holding register (reading data of holding registers) (H03 or 03)
●
Query message
●
Normal response (Response message)
●
Query message setting
●
Content of normal response
Transaction
identifier
Protocol
identifier
Length field
Unit
identifier
Function
Starting
address
No. of points
H
(8 bits)
L
(8 bits)
H
(8 bits)
L
(8 bits)
H
(8 bits)
L
(8 bits)
(8 bits)
H03
(8 bits)
H
(8 bits)
L
(8 bits)
H
(8 bits)
L
(8 bits)
Transaction
identifier
Protocol
identifier
Length field
Unit
identifier
Function
Byte
count
Data
H
(8 bits)
L
(8 bits)
H
(8 bits)
L
(8 bits)
H
(8 bits)
L
(8 bits)
(8 bits)
H03
(8 bits)
(8 bits)
H
(8 bits)
L
(8 bits)
...
(n × 16
bits)
Message Description
Transaction identifier
The master adds the data for the purpose of transaction control.
The same data is returned in the response from the slave.
Protocol identifier
Fixed to 0. (When the slave receives data other than 0, it does not send the response
message.)
0 is returned in the response from the slave.
Length field The data length from the unit identifier to the data is stored in byte.
Unit identifier Fixed to 255
Function Set H03.
Starting address
Set the holding register. address from which to start reading of data.
Starting address = start register address (decimal) – 40001
For example, when start register address 0001 is set, the data of holding register address
40002 is read.
No. of points Set the number of holding registers to read. Data can be read from up to 125 registers.
Tab. 5-312: Description of the query message
Message Description
Byte count
The setting range is H02 to HFA (2 to 250).
Twice the number of reads specified by
is set.
Data
The amount of data specified by is set. Read data is output Hi bytes first followed by Lo
bytes, and is arranged as follows: data of start address, data of start a 1, data of start
a 2, and so forth.
Tab. 5-313: Description of normal response