What is the RS232, RS422, RS485 solution

1, RS-232-C

RS-232-C is the American Electronics Industry Association EIA (Electronic Industry Association) to develop a kind of serial physical interface standard. RS is in English "recommended standard" abbreviation, 232 for the identification number, C indicated that the number of changes. RS-232-C bus standard equipped with 25 signal lines, including a main channel and an auxiliary channel.

In most cases, mainly in the main channel, for general duplex communication, only a few signal lines can be achieved, such as a transmission line, a receiving line and a ground wire.

RS-232-C standard specifies the data transfer rate per second 50,75,100,150,300,600,1200,2400,4800,9600,19200 Porter.

RS-232-C standard requirements, the drive allows 2500pF capacitive load, communication distance will be affected by this capacitance limits, for example, use of 150pF / m communication cable, the maximum communication distance of 15m; if the cable capacitance per meter decreases communications distance can be increased. Another reason for the short transmission distance is the RS-232 is a single-ended signal transmission, there is common ground can not suppress common mode noise and interference problems and therefore are generally used for communication within 20m.

2, RS-485

RS-485 bus, demands for the communication distance of tens of meters to the previous 1000 meters, the widely used RS-485 Serial Bus

RS-485 uses differential balanced send and receive, and therefore has the ability to suppress common mode interference. Bus Transceiver with high sensitivity, can detect voltages as low as 200mV, so the signal can be transmitted outside of 1000 meters to be restored.

RS-485 half-duplex mode, any time there can be only one point in the sending state, therefore, to send the circuit to be controlled by the enable signal.

RS-485 for multi-point interconnection is very convenient, you can dispense with a number of signal lines. Application of RS-485 can constitute a network distributed system, which allows a maximum of 32 drives in parallel, and 32 sets receiver.

3, RS-422

RS422 bus, RS485, and RS422 circuit is basically the same principles are based on differential way to send and receive without digital ground.

Differential is the same rate of transmission distance and under the conditions of the root causes, which is the fundamental difference between the two with the RS232, because RS232 is a single-ended input and output, duplex digital ground at least at work. A transmission line and receive line 3 line (asynchronous transmission), you can also add other control lines to complete the synchronization functions.

RS422 full-duplex through the work of two pairs of twisted pair transceiver can not affect each other, but only half-duplex RS485 work, income can not be made at the same time, but it only needs a pair of twisted-pair.

RS422 and RS485 can be transmitted in the 19kpbs under 1,200 meters. Line with the new transceiver devices can be connected.