(N) Operation via communication and its settings
42
Read holding register (reading data of holding registers) (H03 or 03)
• Query message
• Normal response (Response message)
• Query message setting
• Content of normal response
a. Transaction
identifier
b. Protocol
identifier
c. Length
field
d. Unit
identifier
e. Function
f. Starting
address
g. 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)
a. Transaction
identifier
b. Protocol
identifier
c. Length
field
d. Unit
identifier
e. Function
h. Byte
count
i. 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
a
Transaction identifier
The master adds the data for the purpose of transaction control.
The same data is returned in the response from the slave.
b
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.
c
Length field
The data length from the unit identifier to the data is stored in byte.
d
Unit identifier
Fixed to 255
e
Function
Set H03.
f
Starting address
Set the holding register address from which to start reading the 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.
g
No. of points
Set the number of holding registers for reading data. Data can be read from up to 125
registers.
Message
Description
h
Byte count
The setting range is H02 to HFA (2 to 250).
Twice the number of reads specified by (g) is set.
i
Data
The amount of data specified by (g) 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 1, data of
start 2, and so forth.
Example) Read the register values of 41004
(Pr.4)
to 41006
(Pr.6)
from slave address 17 (H11).
Query message
A given value is set.
Normal response (Response message)
The values are the same as those in the query message.
Read value
Register 41004
(Pr.4)
: H1770 (60.00 Hz)
Register 41005
(Pr.5)
: H0BB8 (30.00 Hz)
Register 41006
(Pr.6)
: H03E8 (10.00 Hz)
Transaction
identifier
Protocol
identifier
Length
field
Unit
identifier
Function
Starting
address
No. of points
H00
(8 bits)
H00
(8 bits)
H00
(8 bits)
H06
(8 bits)
H11
(8 bits)
H03
(8 bits)
H03
(8 bits)
HEB
(8 bits)
H00
(8 bits)
H03
(8 bits)
Transaction
identifier
Protocol
identifier
Length
field
Unit
identifier
Function
Byte
count
Data
H00
(8 bits)
H00
(8 bits)
H00
(8 bits)
H09
(8 bits)
H11
(8 bits)
H03
(8 bits)
H06
(8 bits)
H17
(8 bits)
H70
(8 bits)
H0B
(8 bits)
HB8
(8 bits)
H03
(8 bits)
HE8
(8 bits)
