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6
XOR is calculated with the next data and X. This is assumed as X.
7
3
Repeat steps
8
3
Repeat steps
9
Set X as CRC-16 to the end of message in sequence from low order to high order.
(6) RTU mode message example
1
Reading (Address 1, PV)
• A request message from the master
The number of data indicates the data item to be read, and it is fixed as (0001H).
3.5 idle
Slave
address
characters
(01H)
1
• Response message from the slave in normal status [When PV=600
The number of response bytes indicates number of bytes of the data which has been read, and
it is fixed as (02H).
Slave
3.5 idle
characters
address
(01H)
1
• Response message from the slave in exception (error) status (When data item is mistaken)
The function code MSB is set to 1 for the response message in exception (error) status (83H).
If an exception code (02H: Non-existent data address) is returned, the error can be determined
by reading this code.
3.5 idle
Slave
characters
address
(01H)
1
2
Reading (Address 1, SV1)
• A request message from the master
The number of data indicates the data item to be read, and it is fixed as (0001H).
3.5 idle
Slave
address
characters
(01H)
1
• Response message from the slave in normal status [SV1=600
The number of response bytes indicates number of bytes of the data which has been read, and it
is fixed as (02H).
3.5 idle
Slave
characters
address
(01H)
1
• Response message from the slave in exception (error) status (When data item is mistaken)
The function code MSB is set to 1 for the response message in exception (error) status (83H).
If an exception code (02H: Non-existent data address) is returned, the error can be determined
by reading this code.
3.5 idle
Slave
characters
address
(01H)
1
3
Setting (Address 1, SV1)
• A request message from the master: When setting SV1 to 600
3.5 idle
Slave
characters
address
(01H)
1
• Response message from the slave in normal status
Slave
3.5 idle
characters
address
(01H)
1
5
to
.
5
to
up to the last data.
Function
Data item
code
(03H)
(0080H)
1
2
(Fig. 6.4-2)
Function
Number of
response bytes
code
(03H)
(02H)
1
1
(Fig. 6.4-3)
Function
Exception
code
code
(83H)
(02H)
1
1
(Fig. 6.4-4)
Function
Data item
code
(03H)
(0001H)
1
2
(Fig. 6.4-5)
Function
Number of
code
response bytes
(03H)
(02H)
1
1
(Fig. 6.4-6)
Function
Exception
code
code
(83H)
(02H)
1
1
(Fig. 6.4-7)
Function
Data
code
item
(06H)
(0001H)
1
2
(Fig. 6.4-8)
Function
Data
code
item
(06H)
(0001H)
1
2
(Fig. 6.4-9)
Number of
Error check
data
CRC
(0001H)
(85E2H)
2
2
Error check
Data
CRC
(0258H)
(B8DEH)
2
2
Error check
3.5 idle
CRC
characters
(C0F1H)
Number of
2
characters
Number of
Error check
data
CRC
(0001H)
(D5CAH)
2
2
(0258H)]
Error check
Data
CRC
(0258H)
(B8DEH)
2
2
Error check
3.5 idle
CRC
characters
(C0F1H)
Number of
2
characters
(0258H)
Error check
3.5 idle
Data
CRC
characters
(0258H)
(D890H)
Number of
2
2
characters
3.5 idle
Error check
Data
CRC
characters
(0258H)
(D890H)
Number of
2
2
characters
8
3.5 idle
characters
Number of
characters
(0258H)]
3.5 idle
characters
Number of
characters
3.5 idle
characters
Number of
characters
3.5 idle
characters
Number of
characters
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