Hệ điều hành - What is modbus

Nội dung text: Hệ điều hành - What is modbus

1. Supervisory Control & Data Acquisition Communication Technology Modbus Protocol
2. What is Modbus ? An open data communication protocol developed in 1979 Published by Modicon Open structure Flexible Widely known Supplied by many SCADA and HMI software Have OPC Servers 2 serial transmission modes: ◼ ASCII ➔ 10 bits ◼ RTU (Binary) ➔ 11 bits Communication interface ◼ RS-232/485 ◼ Ethernet (TCP/IP)
3. Application structure (general) Modbus Client (Master) SCADA HMI RS-232/485 Internet Modbus Device (Slave) Modbus Device (Slave)
4. Query-Response Cycle Query Station Number Function Code Data Bytes Station Number (Flexible) Function Code Data Bytes (Flexible) Error Check Error Check Response
5. Hardware classification Station Device: 0 ~ 255 Digital input ◼ 1xxxx: 4 digits for hexadecimal address (0000 ~ FFFF) ◼ 1xxxxx: 5 digital for decimal address (0 ~ 65535) Digital output ◼ 0xxxx: 4 digits for hexadecimal address (0000 ~ FFFF) ◼ 0xxxxx: 5 digital for decimal address (0 ~ 65535) Analog input ◼ 4xxxx: 4 digits for hexadecimal address (0000 ~ FFFF) ◼ 4xxxxx: 5 digital for decimal address (0 ~ 65535) Analog output ◼ 3xxxx: 4 digits for hexadecimal address (0000 ~ FFFF) ◼ 3xxxxx: 5 digital for decimal address (0 ~ 65535)
6. Two serial transmission modes ASCII Mode ◼ Data system ASCII character, ‘0’~’9’,’A’~’F’ ◼ Bits per data unit 1 Start Bit 7 Data Bits 1 Parity Bit (Even/Odd) 1 Stop Bit 1 Start Bit 7 Data Bits 2 Stop Bit ◼ Error Check Field Longitudinal Redundancy Check (LRC) RTU Mode ◼ Data system 8-bit Binary, 00~FF ◼ Bits per data unit 1 Start Bit 8 Data Bits 1 Parity Bit (Even/Odd) 1 Stop Bit 1 Start Bit 8 Data Bits 2 Stop Bit ◼ Error Check Field Cyclical Redundancy Check (CRC)
7. Modbus Message Packet ASCII Mode Start Station Number Function Code Data Error Check End 1 Char 2 Chars 2 Chars n Chars 2 Chars 2 Chars : LRC CR,LF RTU Mode Start Station Number Function Code Data Error Check End 3.5 Char 8 Bits 8 Bits n x 8 Bits 2 x 8 Bits 3.5 Chars Silence CRC Silence Modbus Plus network Prefixed Data Station Number Function Code Data 6 x 8 Bits Byte 0, 1: transaction ID – usually 0 Byte 2, 3: protocol ID = 0 Byte 4, 5: number of bytes following
8. Read/Write Modes Single Read/Write Multiple Read/Write
9. Basic application #1 Modbus/TCP Clients (Masters) Modbus/TCP command protocol Internet Default Firmware Modbus/TCP Slave Device
10. Basic application #2 Modbus/TCP Clients (Masters) Serial Device Clients (Masters) Modbus/TCP command protocol Command protocol depend on serial devices Internet Default Modbus/TCP Slave Device Firmware Serial Remote Device Virtual Comm Technique
11. Modbus SDK
12. Modbus Embedded Controller Modbus Client (Master) Modbus protocol User-defined protocol SCADA HMI Modbus Embedded Controller Check Modbus Request Update I/O RS-485 Run User Process . . . RS-232 PLC
13. Advanced application Modbus/TCP Clients (Masters) General TCP/IP Client (Masters) Serial Device Clients (Masters) Modbus/TCP Slave Internet User-defined TCP/IP Slave Special Firmware modified by users Modbus/RTU Master Serial Device Master
14. Modbus Resources Web page of original Modbus protocol inventor, MODICON Inc. A community for Modbus users ActiveX freeware to communicate with equipments via Modbus(RTU/ASCII) or Modbus/TCP Example C code for Linux Modbus/RTU communication