Read Input Registers (Fc: 04) - Mitsubishi QJ71MB91 User Manual

4
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
(2) Response message format (Slave
4
- 21 4.7 Read Input Registers (FC: 04)
Function code
Function Head input register number
code (0000 to FFFF
H
(04 )
H
(H)
Figure 4.18 Read input registers (Request message)
(When completed normally)
Function code
Function Number of
code read bytes
1
(04 ) n x 2 *
H
Figure 4.19 Read input registers (Normal response message)
(When completed with an error)
Function code Data
Function
Exception
code
code * 2
(84 )
H
Figure 4.20 Read input registers (Exception message)
* 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
Slave)
Data
Read points
) (0001 to 007D
H H
(L) (H)
Master)
Data
Device data
. . .
1
(H) (L)
(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
(L)
Device data
n
(L)
(H)