Longtec TR700 - Modbus Protocol

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TR700 Instruction Manual

6.4.2. Modbus Protocol

6.4.3.1. Signal Format

Data bit = 8;

Parity bit = 1(non, even or odd);

Stop bit = 1;

Code standard = hexadecimal.

8-bit no parity, 8-bit odd parity and 8-bit even parity are optional.

6.4.3.2. Datagram Format

TR700 Modbus protocol is in RTU ( Remote Terminal Unit) communication mode.。A byte (8 bits)

in the message contains two 4-bit hexadecimal characters.

RTU Mode

Address

Function code The number of data Data 1 ... Data n CRC high byte

CRC low

byte

Address Domain Function Domain Data Domain Fault Checking

Domain

The delimitation of frame: In the mode of MODBUS，the interval between two characters’ sending

or receiving can not exceed 1.5 times of the transmitting time of every character. If it exceeds 3.5

times of the transmitting time of every character, it is considered that the data of this frame has been

all received and a new frame starts transmitting.

Startup bit 1 2 3 4 5 6 7 8 Parity bit Stop bit

The bit serial number in the RTU mode with parity bit

Startup bit

Stop bit

The bit serial number in the RTU mode without parity bit

List of Communication Parameter of TR700 Modbus

Address

code

Data domain

The code

of reading function

The code

of writing

function

03 06 16

40001 Display the higher 16 bits Y - -