Mitsubishi QJ71MB91, User Manual

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- 21 4.7 Read Input Registers (FC: 04)
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MODBUS(R) STANDARD FUNCTIONS
4.7 Read Input Registers (FC: 04)
Reads the values of one or more input registers.
(1) Request message format (Master Slave)
(2) Response message format (Slave Master)
(When completed normally)
(When completed with an error)
* 2 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 4.18 Read input registers (Request message)
Figure 4.19 Read input registers (Normal response message)
Figure 4.20 Read input registers (Exception message)
Data
(L) (L)
Function code
Function
code
(04
H
)
Head input register number
(0000
H
to FFFF
H
)
Read points
(0001
H
to 007D
H
)
(H) (H)
Data
Function code
Function
code
(04
H
)
. . .
(L) (L)
Number of
read bytes
n x 2 *
1
Device data
1
Device data
n
(Number of read bytes n x 2)
*1 For example, if n = 4, the number of read
bytes is calculated as 4 x 2 = 8 bytes.
(H)
(H)
Data Function code
Function
code
(84
H
)
Exception
code *
2