The interface and protocol have the same meaning here, no need to mince words
RS485:
In response to the shortcomings of RS-232-C, some new interfaces have emerged continuously Standard, RS-485 is one of them, it has the following characteristics:
1. Electrical characteristics of RS-485: Logic "1" is based on the voltage difference between the two lines as + (2-6) V Represents; logic "0" is represented by the voltage difference between the two lines as - (2-6) V. The interface signal level is lower than RS-232-C, which makes it less likely to damage the chip of the interface circuit. Moreover, the level is compatible with the TTL level and can be easily connected to the TTL circuit.
2. The maximum data transmission rate of RS-485 is 10Mbps
3. The RS-485 interface uses a combination of balanced drivers and differential receivers to resist interference and interference Enhanced, that is, good resistance to noise interference.
4. The standard maximum transmission distance of the RS-485 interface is 4000 feet, which can actually be up to 3000 meters. In addition, the RS-232-C interface only allows one transceiver to be connected to the bus, that is, a single station ability. The RS-485 interface allows up to 128 transceivers to be connected to the bus. That is, it has multi-station capability, so users can easily establish a device network using a single RS-485 interface.
Because the RS-485 interface has good immunity to noise interference, long transmission distance and multi-station capability, it has become the preferred serial interface. Because the half-duplex network composed of the RS485 interface generally only requires two connections, the RS485 interface uses shielded twisted pairs for transmission. The RS485 interface connector uses a DB-9 9-pin plug socket, the RS485 interface with the smart terminal uses DB-9 (hole), and the keyboard interface RS485 connected to the keyboard uses DB-9 (pin).