Understanding RS485 Standard and Working of RS485 Transceiver - Embedded Hardware Design > 자유게시판

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We connect the generator to the input of the microcircuit, and look at the output signal. Against this, in full-duplex systems slave and host devices communicate with each other using the dedicated output and input lines. From a hardware point of view, full-duplex RS-485 has some major advantages over RS-232 -- it can communicate over much longer distances at higher speeds. The network can be configured as a two-wire or four-wire network. If both the driver and receiver of the devices on the network have no inversion, (or If both the driver and receiver of the devices are inverted) then the A and B lines of the devices should be connected together. Integrate a solid and reliable micro PLC with your existing machines, devices and production lines - also in combination with other elements in the modular and versatile Arduino ecosystem, from small and smart sensor-packed modules to SOMs to gateways, for end-to-end solutions that can be customized to meet any need. Through use of a symmetrical transmission procedure in combination with low-capacitance and low-attenuation, twisted-pair cables, extremely reliable connections over long distances at high transmission rates can be achieved over a distance of up to 500 m. The physically quite similar RS422 standard is based on the following data: AWG24, twisted-pair phone cable with 52.5pF/meter and 100Ohm impedance.

However, four-wire networks may feature two twisted pair wires, where a master port with s transmitter is connected to slave receivers of one twisted pair and the slave transmitters are connected to the master receive of the second twisted-pair wire. The master initiates a communications request to a "slave node" by addressing that unit. The master device sends a request to a specific slave device by transmitting a packet of data over the communication line. Over the years, various serial communication protocols have gained priority. In most cases, RS485-based devices can employ communication protocols like Modbus and ASCII to establish communication with a central control system. 3) The standard value of the maximum transmission distance of the RS485 interface is 4000 feet, which can actually reach 3000 meters. The maximum recommended distance was 1.2km or 4000 feet and the data rate was limited to 100kbps. Over the years, the standard and its data transmission speed have evolved for the better.

Maximum Recommended Data Rate: In 1998, when the standard was introduced, the maximum recommended data rate was 10Mbps, and it could be achieved with a cable length of 12 meters or 40 feet. It’s reasonable to question why one wouldn’t simply transmit signals at the quickest possible speed to hasten network updates.The answer lies in the degradation of communication signals due to transmission losses on the cable when the product of the communication trunk length and the baud rate exceeds the recommended limit. The appendix discusses capacitance and resistance of the cable, then gives an example calculation where the capacitance of the cable per foot (30pF/foot) multiplied by the cable's length, plus the capacitance of the receiver (100pF) gives a maximum cable length of 80 feet. But since the receiver chips are sensitive to a shift in the ground potentials, reliable installations strongly dictate that galvanic isolation as defined in ISO 9549 be implemented. In a two-wire network, the receiver and the transmitter are connected to one twisted pair wire. Receiver Input Sensitivity: RS-485 has a receiver input sensitivity of ±200mV, which means a receiver must see signals above or below 200mV to recognize a mark.

When a HIGH logic level is applied to the R/T pin, the transmitter becomes activated, while the receiver is deactivated at the same time - and vice versa. While a lot has been written about RS232, RS485 is sparingly discussed. Data Transmission: RS-485 standard assures differential data transmission, which is quite effective while communicating high data rates over large distances. Differential data transmission refers to balanced differential signals, which can help minimize induced noise signals and ground shifts. 2) The RS485 interface adopts a combination of a balanced driver and a differential receiver, which has strong anti-common-mode interference ability, that is, good anti-noise performance. RS-232 serial cabling interface came into existence in the year 1962. It is known to be the oldest cabling method to form a connection between data terminal equipment and data communication equipment. I'd imagine that you'd need adapters for different pieces of equipment from different manufacturers to talk to each other. VERSITRON is one of the most popular manufacturers of RS-485 standard devices such as 4 channel phone kits with RS485 data transmission capabilities, RS-485 2-wire telephone modems, and so on.

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