RS485is a physical interface, simply said to be hardware.
MODBUSis an international standard communication protocol for exchanging data between different vendors (typically industrial use); so-called agreements can also be understood as the "language" mentioned above, it is simply software.
RS485 belongs to the wired transmission, so it is necessary to hardware transmission media, the actual is two lines on it, in this two is the actual transmission line is the same signal, just send the signal in two, but the receiver will restore it to the original signal, the benefits of doing so and RS232 to compare , RS232 also need two lines, more time to add ground, so it is three lines, ground I regardless of it, the remaining two only one line transmission of data signal, and the other transmission of the clock, that is, the signal of what the original send end of how to send out, the same receiving end also do the same processing. So 485 of the receiver can be transmitted by the signal in the transmission of interference can be offset, and 232 of the receiving side can not, so 485 of the anti-jamming ability to transmit the signal thousands of meters, and 232 can only transmit more than 10 meters.
Modbus is just one kind of communication protocol, like Chinese and English, is a language of communication, a language of communication between machines. Then there must be a bridge of communication before the exchange, that is the transmission medium 485 or 232 or other electrical rules, the same protocol can be used in different transmission media such as 485 or 232 but the same transmission line cannot exist simultaneously two protocols.
in general, two devices transmit data through the Modbus protocol:The earliest is the use of RS232C as a hardware interface, (that is, the general computer serial communication port (serial));also useful for RS422,also has the commonly used RS485, this kind of interface transmits the distance far, in the general industrial field uses more. Modbus Protocol also sub-Modbus Rtu,modbus ASCII and later developed Modbus TCP three modes: one of the first two (Modbus Rtu,modbus ASCII) The physical hardware interface used is a serial (Serial) communication port (rs232,rs422,rs485). Modbus TCP is to adapt to the current world development trend, what can be used Ethernet network or the Internet to connect, transfer data. So also Modbus TCP mode, the hardware interface of this mode is Ethernet (Ethernet) port, that is, our computer general use of the network port.
