Mitsubishi Electric FR-A820-00046 Instruction Manual page 991

Parameters
Read holding register (reading data of holding registers) (H03 or 03)
● Query message
³ Transaction
identifier
H
(8 bits)
● Normal response (Response message)
³ Transaction
identifier
H
(8 bits)
● Query message setting
Message
³ Transaction identifier
· Protocol identifier
» Length field
¿ Unit identifier
´ Function
² Starting address
¶ No. of points
Tab. 5-370: Description of the query message
● Content of normal response
Message
º Byte count
¾ Data
Tab. 5-371: Description of normal response
FR-A800
· Protocol
» Length field
identifier
L H L H
(8 bits) (8 bits) (8 bits) (8 bits)
· Protocol
» Length field
identifier
L H L H
(8 bits) (8 bits) (8 bits) (8 bits)
Description
The master adds the data for the purpose of transaction control.
The same data is returned in the response from the slave.
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.
The data length from the unit identifier to the data is stored in byte.
Fixed to 255
Set H03.
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.
Set the number of holding registers to read. Data can be read from up to 125 registers.
Description
The setting range is H02 to HFA (2 to 250).
Twice the number of reads specified by ¶ is set.
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 address + 1, data of start
address + 2, and so forth.
¿ Unit
´ Function
identifier
L
(8 bits)
(8 bits)
¿ Unit
´ Function
identifier
L
(8 bits)
(8 bits)
Ethernet communication (FR-A800-E)
² Starting
address
H03 H L
(8 bits) (8 bits) (8 bits)
º Byte
¾ Data
count
H03 H
(8 bits)
(8 bits) (8 bits)
¶ No. of points
H L
(8 bits) (8 bits)
...
L
(n × 16
(8 bits)
bits)
5 - 789