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ManualsBrandsEmerson ManualsNetwork CardOpenComms-485

36 NIC Setup and Testing

RTU Framing Examples

READ REGISTERS (FUNCTION CODE 0X03 &

0X04)

Query: for reading holding /input registers (requested by a client)

Server

Addres

Function

Code

(0x3/0x4)

Index of

starting register

Number of

registers to be read

16 bit

CRC

1 byte 1 byte 2 bytes 2 bytes 2

bytes

Response: for reading holding/input registers (response by the server)

Server

Addres

Function

Code

(0x3/0x4)

Byte

Count

Data from registers 16 bit

CRC

1 byte 1 byte 1

bytes

2*m bytes (= Byte Count) 2 bytes

WRITE SINGLE HOLDING REGISTER

(FUNCTION CODE 0X06)

Query: for writing a single holding register (requested by a client)

Server

Addres

Function

Code

(0x06)

Index of the

16 bit value to

be written

16 bit CRC

1 byte 1 byte 2 bytes 2 bytes 2 bytes

Response: for writing a holding registers (response by the server)

Server

Addres

Function

Code

(0x06)

Index of the

16 bit value

been written

16 bit CRC

1 byte 1 byte 2 bytes 2 bytes 2 bytes