Mitsubishi QJ71MB91, User Manual

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- 19 4.5 Read Discrete Inputs (FC: 02)
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MODBUS(R) STANDARD FUNCTIONS
4.5 Read Discrete Inputs (FC: 02)
Reads the status (ON/OFF) of one or more inputs.
(1) Request message format (Master Slave)
(2) Response message format (Slave Master)
(When completed normally)
(When completed with an error)
* 1 Exception and error codes are stored in the buffer memory in the case of error completion.
Refer to the following for storage location, confirmation methods, and detailed contents.
Section 11.4
Figure 4.12 Read discrete inputs (Request message)
Figure 4.13 Read discrete inputs (Normal response message)
Figure 4.14 Read discrete inputs (Exception message)
Data
(L) (L)
Function code
Function
code
(02
H
)
Head input number
(0000
H
to FFFF
H
)
Read points
(0001
H
to 07D0
H
)
(H)
(H)
Data
b0 b1 b2 b3 b4 b5 b6 b7
Function code
Function
code
(02
H
)
Number of
read bytes
n
Device data
1
Device data
n
(Number of read bytes n)
(Device data 1 to n)
Device data 1
Device data n
Bit device
storage order
0 : OFF
1 : ON
The read input statuses are stored in order from low-order to high-order bits.
When the number of read points is not a multiple of 8, the excess bits turn to 0.
Data
Function code
Function
code
(82
H
)
Exception
code*
1