Read Discrete Input Status (0X02); Read Holding Registers (0X03); Force (Write) Single Coil (0X05) - INVT IVC2H Programming Manual

Programming manual of IVC series small PLC
2. Response frame
If the read address is not the times of 8, the remaining bits will be filled with 0 (starting with the high bits).
Function code
Address
(01H)

3.2 Read discrete input status (0x02)

In the PLC of GCM series, it specially refers to X element. The function code only supports the read function of X element with
the maximum read number of 256.
1. Request frame
Address
2. Response frame
If the read address is not the times of 8, the remaining bits will be filled with 0 (starting with the high bits).
Function code
Address
(02H)

3.3 Read holding registers (0x03)

It refers to reading the value of data (word) register at the slave station, with the maximum number of registers of 125 read each
time. It does not support broadcast.
1. Request frame
Address
2. Response frame
Address Function code (03H)

3.4 Force (write) single coil (0x05)

Force (Write) single coil writes bit element value to the slave station and supports broadcast, i.e. writing the same element to all
slave stations. It supports 1 bit element at most.
1. Request frame
Address
Note: The written value of the element is 0xFF00 (ON, 1) or 0x0000 (OFF, 0).
2. Response frame
Response frame is the repeat of request frame.
Address
Appendix 7 Modbus communication protocol (IVC1, IVC2L series)
Number of bytes read
(n)
Function code (02H)
Number of bytes read
(n)
Function Code (03H)
Number of bytes read (n)
Function code (05H)
Function code (05H)
Read data
......
No.1
B7 B6 B5 B4
Starting address Number of elements
H L
Read data
...
No.1
B7 B6 B5 B4
Starting address Number of elements
H L H
Read data No.1
...
H L
Starting address Written element value
H L H
Starting address Written element value
H L H
Read data
Check code
(CRC or LRC
No.n
B3 B2 B1 B0
Check code
(CRC or LRC)
H L
Check code
Read data
(CRC or LRC
No.n
B3 B2 B1 B0
Check code
L (CRC or LRC)
Read data No.n
(CRC or LRC)
H L
Check code
(CRC or LRC)
L
Check code
L (CRC or LRC)
357
Check code