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RS485 in full duplex mode 4 contacts are employed. Figure 4 is a pin diagram for both 25 pin RS485 pinout half duplex and full duplex pinout connectors. Pinout connects to DB9 and DB25 connectors with 2 and 4 contacts. Connect RS485 devices with 4 contacts. Connect RS485 devices with 2 contacts. If you’re very sure that you are only using RS485 then you will not be disappointed with the former. The WattNode® BACnet and Modbus® meters communicate using RS-485 (TIA/EIA-485-A) half-duplex, differential signaling at 9600, 19200, 38400, and 76,800 baud. As displayed in the RS485 cable pinout, the interface has all signals in differential configurations. Multi-drop configurations enable up to 32 devices to be connected with a single controlling master device. RS485 is primarily used in multi-drop configurations that make use of its balanced differential interface. The RS422 protocol has similarities with RS485 in that both conduct data transmission using differential signals. The distances these signals are carried is greater due to differential signals. The RS485 (EIA485) interface has proved to be extremely robust and is the most popular communication protocol used in industry due to its multi-point topology. What are serial communication protocols? Wire protocols are guidelines for the transmission of data from point to point.

Now there was certain instances I used STP wire for rs485 because I had a lot of devices connected in a long run chain (DMX512 lighting fixtures). The RS485 employs a set of 120 Ohm termination resistors located at each end of the line. Normally, this connection is made at one end of the main cable. The end resistance must be used only at the ends of the main cable. The RS485 network must be designed as one line with multiple drops, not as a star. A Modbus RS485 connects a Master device to one or more Slave devices. 2. The network topology supported by RS-232 is a point-to-point type because it simply connects two devices. The benefit of this particular type of cable is that it supports communications for distances up to 1,200 meters or 3,900 feet. Transmission speeds of 30-35 Mbps are supported for distances of up to 10 meters. This is necessary to allow long-distance data transmission.

All other nodes receive these data. Currently available high-resistance RS485 inputs allow this number to be expanded to 256.RS485 repeaters are also available which make it possible to increase the number of nodes to several thousands, spanning multiple kilometers.And that with an interface which does not require intelligent network hardware: the implementation on the software side is not much more difficult than with RS232. Using a repeater, the main cable is divided into different segments, each of which can be up to 700 m in length and connect 32 devices (this number includes the repeaters). An RS485 cable schematic includes information such as the type of cable being used, the number of signal wires, the length of the cable, and how they should be interconnected. If you need more information on the cable & protocol, refer to the article below. This means that if you have 3 meters to connect to a PC, you will need 3 ports, or at least, an RS232 multiplexor. Full-duplex mode is used when you need to be able to transmit and receive data at the same time.

In order to avoid errors when many devices are connected, cables of the same colour should be used for all the connections to the terminals A and cables of the same colour should be used for all the connections to the terminals B of the various devices (e.g. white for A and blue for B). 100 ohms, Cat 5 cables almost meets the electrical requirements for RS-485 cables. 24 AWG solid wires, which are typically used in Cat 5 cables, can break easily when connected to a screw terminal block, which does not provide any strain relief. At Keystone, we supply UL2464 Single Pair Signal cables, UL2464 Multi Pair - OS Signal cables, and RS485 Multi Pair Double Overall Screened cables (sample construction below). Cables following these protocols are robust and can transmit data over long distances and in noisy environments. So 80m is the practical limit for CAT6 cables. At earlier times, prefix RS was used before cabling standards. This makes it easier to identify cabling errors. It is faster and much more versatile than the older RS232. Their main difference boils down to one having only support for RS485, while the other one supports RS232 and TTL as well.