The receiver input impedance is 4k, so the maximum load capacity of the transmitter is 10 TImes; 4k 100 (terminating resistor).
![]() Difference Between Fast Ethernet And Serial Interface Serial Data CommunicationBlog What is the difference between RS-232, RS-422, and RS-485 Posted on 2018-10-07 2018-09-11 by Optcore 07 Oct RS232 overview The RS-232 interface complies with the interface standard for serial data communication established by the Electronic Industries Alliance (EIA).It is widely used for computer serial interface peripheral connections.Connect cables and mechanical, electrical, signal, and transfer processes.
The data transmission rate specified by the RS-232-C standard is 50, 75, 100, 150, 300, 600, 1200, 2400, 4800, 9600, 19200 baud per second. RS232 features: RS-232 is one of the mainstream serial communication interfaces. Due to the early appearance of the RS232 interface standard, it is inevitable that there are deficiencies, mainly the following four points: (1) The signal level of the interface is high, which is easy to damage the chip of the interface circuit. The voltage of any signal line on the RS232 interface is in a negative logic relationship. That is: the logic 1 is -3 15V; the logic is 0: 3 15V, and the noise margin is 2V. That is, the receiver is required to recognize a signal higher than 3V as a logic 0, a signal lower than -3V as a logic 1, a TTL level of 5V as a logic positive, and 0 as a logic negative. Incompatible with the TTL level, a level shifting circuit is required to connect to the TTL circuit. The transmission rate is low. In asynchronous transmission, the bit rate is 20Kbps; therefore, in the 51CPLD development board, the integrated program baud rate can only be 19200, which is also the reason. The interface uses a signal line and a signal return line to form a common ground transmission form. This common ground transmission is prone to common mode interference, so the noise immunity is weak. The transmission distance is limited. RS485 overview The RS-485 serial bus is widely used when the communication distance is required to be several tens of meters to several kilometers. RS-485 uses balanced transmit and differential receive, so it has the ability to reject common-mode interference. In addition to the high sensitivity of the bus transceiver, it can detect voltages as low as 200mV, so the transmitted signal can be recovered beyond the kilometer. RS-485 uses a half-duplex mode of operation, and only one point can be sent at any time. Therefore, the transmitting circuit must be controlled by an enable signal. RS485 features RS-485 is very convenient for multi-point interconnection and can save many signal lines. Applications RS-485 can be networked to form a distributed system that allows up to 32 drives and 32 receivers to be connected in parallel. In response to the shortcomings of RS-232-C, the new standard RS-485 has the following features: (1) Electrical characteristics of RS-485: The logic 1 is represented by the voltage difference between the two lines 2V6V, and the logic 0 is represented by the voltage difference between the two lines -6V-2V. Difference Between Fast Ethernet And Serial Interface Full Name OfRS422 overview The full name of the RS-422 standard is the electrical characteristics of the balanced voltage digital interface circuit, which defines the characteristics of the interface circuit. Difference Between Fast Ethernet And Serial Interface Driver Has ASince the receiver uses high input impedance and the transmission driver has a stronger driving capability than RS232, it is allowed to connect multiple receiving nodes on the same transmission line, and up to 10 nodes can be connected. One master device (Master) and the rest slave devices (Slave), the slave devices cannot communicate with each other, so RS-422 supports point-to-multidirectional two-way communication.
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