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:

 

 

 

 

 

 

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

11

Write Data 01 (Lo)

(by default: value of the control word (CMd))

……………………

……………………

72

Write Data 32 (Hi)

PKW output: PKE (Hi)

73

Write Data 32 (Lo)

PKW output: PKE (Lo)

Response format:

 

 

 

 

 

 

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)

Exception response format:

 

 

 

 

 

Byte

Meaning

With the VW3A3310d Ethernet card

0

Function Code = 16#97

 

 

 

 

01

(Illegal Function)

1

Exception Code

02

(Illegal Data Address)

03

(Illegal Data Value)

 

 

 

 

04

(Illegal Response Length)

 

 

 

 

38

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Image 38
Schneider Electric VW3A3310d user manual Read/Write Multiple Registers 23 = 16#17 function