(N) Operation via communication and its settings
46
Read holding register access log (H46 or 70)
• Queries by function codes H03 and H10 are supported.
The number and start address of holding registers successfully accessed by the previous communication are returned.
"0" is returned for both the number and start address for queries other than the function codes above.
• 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
H
(8 bits)
L
(8 bits)
H
(8 bits)
L
(8 bits)
H
(8 bits)
L
(8 bits)
(8 bits)
H46
(8 bits)
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)
H46
(8 bits)
H
(8 bits)
L
(8 bits)
H
(8 bits)
L
(8 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 H46.
Message
Description
f
Starting address
The start address of the holding register that was successfully accessed is returned.
Starting address = start register address (decimal) - 40001
For example, when start address 0001 is returned, the holding register address that was
successfully accessed is 40002.
g
No. of points
The number of holding registers that were successfully accessed is returned.
Example) Read the successful register start address and number of successful accesses from slave address 25 (H19).
Query message
A given value is set.
Normal response (Response message)
The values are the same as those in the query message.
Two successful reads of start address 41007
(Pr.7)
are returned.
Transaction
identifier
Protocol
identifier
Length field
Unit
identifier
Function
H00
(8 bits)
H00
(8 bits)
H00
(8 bits)
H02
(8 bits)
H19
(8 bits)
H46
(8 bits)
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)
H19
(8 bits)
H10
(8 bits)
H03
(8 bits)
HEE
(8 bits)
H00
(8 bits)
H02
(8 bits)
