38
11. Modbus TCP server
11. 8. “Read/Write Multiple Registers” (23 = 16#17) function
The “Read/Write Multiple Registers” service is reserved for setting up the IO Scanning service (see “IO Scanning” section).
Request format:
Response format:
Exception response format:
Byte Meaning With the VW3A3310d Ethernet card
0 Function Code = 16#17 16#17
1 Read Reference Address Hi 0 (not handled)
2 Read Reference Address Lo 0 (not handled)
3 Quantity to Read Hi (0) 0
4 Quantity to Read Lo (1 - 125) 32
5 Write Reference Address Hi 0 (not handled)
6 Write Reference Address Lo 0 (not handled)
7 Quantity to Write Hi (0) 0
8 Quantity to Write Lo (1 - 100) 32
9 Byte Count (2 × Quantity to Write) 64
10 Write Data 01 (Hi) Value of 1st IO Scanner output register
(by default: value of the control word (CMd))
11 Write Data 01 (Lo)
… …………………… ……………………
72 Write Data 32 (Hi) PKW output: PKE (Hi)
73 Write Data 32 (Lo) PKW output: PKE (Lo)
Byte Meaning With the VW3A3310d Ethernet card
0 Function Code = 16#17 16#17
1 Byte Count (2 × Quantity to Write) 64
2 Read Data 01 (Hi) Value of 1st IO Scanner input register
(by default: value of the status word (EtA))
3 Read Data 01 (Lo)
… …………………… ……………………
64 Read Data 32 (Hi) PKW input: PKE (Hi)
65 Read Data 32 (Lo) PKW input: PKE (Lo)
Byte Meaning With the VW3A3310d Ethernet card
0 Function Code = 16#97
1 Exception Code
01 (Illegal Function)
02 (Illegal Data Address)
03 (Illegal Data Value)
04 (Illegal Response Length)