Modbus (RS-485) protocol
Modbus is a fundamental, open serial communication protocol widely used in industrial automation. It operates on a simple master-slave architecture, where a single master device (like a PLC or SCADA system) requests data from one or multiple slave devices (sensors, actuators, or other controllers). Its simplicity, reliability, and lack of licensing fees have made it the de facto standard for connecting industrial electronic devices.
MODBUS Pressure and Level transmitter communication protocol
- Summary:
All message formats are in accordance with GBZ 19582.1-2004
Modbus Based Industrial Automation Network Specification-Part 1:
Modbus Application Protocol
This protocol complies with the subset RTU mode in the
MODBU-RTU protocol, and the communication mode is the RS485
half-duplex working mode. - Serial data format:
Serial port setting: no check, 8 bit data, 1 bit stop bit. Example: 9600, N, 8,1 meaning: 9600bps, no check, 8 bit data bit, 1
bit stop. The serial port port rate supported by this transmitter is:
1200,2400,4800,9600,19200,38400，
Check bit supported by this transmitter:
N, O, and E: NONE, ODD, and EVEN. Polynomial of CRC check: 0 xA 001. The data in the process of data communication is partially processed
according to the double-byte symbolic plastic data. If the data identifies
floating points, the writing needs to read the decimal point to determine
the size of the data. The other part is floating point number format, floating point number
format is float at format, 4 byte floating point number, large end mode. ABCD byte order. The functional code of the modbus-rtu protocol supported by this
protocol is: 0x03,0x04,0x06,0x10 in total 4 kinds
- Communication format:
3.1 Read the command format (03 / 04 function code) for example
A. Send the read command format:
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