Because of this RS485 and the others can be used in situations with a severe ground level shift of several volts, where at the same time high bit rates are possible because the transition between logical 0 and logical 1 is only a few hundred millivolts. Apart from a one-to-one connection, RS485 can be used with a serial bus that connects to multiple peripherals. Care must be taken that an SC connection, especially over long cable runs, does not result in an attempt to connect disparate grounds together - it is wise to add some current limiting to the SC connection. When the cable is twisted, we see that in some parts of the signal lines the direction of the noise current is the oposite from the current in other parts of the cable. Shielding-which is a common method to prevent noise in RS232 lines-tries to keep hostile magnetic fields away from the signal lines. Failure to stay within this range will result in, at best, signal corruption, and, at worst, damage to connected devices. Because there is a chance of data collosion with this implementation, theory tells us that in this case only 37% of the bandwidth will be effectively used.



































In this article, we will be discussing these protocols in detail and how they are used in industrial control systems. Both of these protocols are used in applications such as data acquisition, automation, and robotics. The selection of standards highly depends on the required data rate. We also see that there is a maximum slew rate defined for both RS232 and RS423. RS232 is an interface to connect one DTE, data terminal equipment to one DCE, data communication equipment at a maximum speed of 20 kbps with a maximum cable length of 50 feet. When you scan the bar code, the information actually gets sent on a 485 transceiver through a long cable to a PC somewhere within the store. RS485 drivers automatically return to their high impedance tri-state within a few microseconds after the data has been sent. The data transmission rates in serial communication protocols vary depending on the protocol and the application.



































It does not specify or recommend any communications protocol; Other standards define the protocols for communication over an RS-485 link. The three most widely used serial communication protocols are RS232, RS485, what is rs485 cable and Modbus. The cabling of the industrial communication systems (Modbus RS485) is different in some ways from the cabling used for power cabling and the electrician may experience some difficulties if he is not an expert in Modbus communication networks. Modbus RTU is a serial communication protocol that uses a binary representation of data to transmit messages between devices. RS485 uses the same DB9 connector used in the RS232 protocol. With Modbus, BACnet and Profibus, A/B labeling refers A as the negative green wire and B as the positive red wire, in the definition of the D-sub connector and M12 circular connector, as can be seen in Profibus guides. Q: Can you convert RS232 to RS485 or vice-versa? First of all we see that the speed of the differential interfaces RS422 and RS485 is far superior to the single ended versions RS232 and RS423. RS485 and RS422 interfaces use differential signaling, which means that they require two wires to transmit data.



































What are the applications of RS485 and RS422 interface? The RS485 serial communication standard has a huge set of applications. How many devices can we connect with the RS485 standard bus? It may be used to control video surveillance systems or to interconnect security control panels and devices such as access control card readers. It is very useful in automation systems as well as to control the variable frequency drivers. It is easy to use and implement, and it is widely supported in industrial control systems. RS-485, also known as TIA-485(-A) or EIA-485, is a standard, originally introduced in 1983, defining the electrical characteristics of drivers and receivers for use in serial communications systems. RS485 is primarily a serial communication standard introduced in 1998 by the Electronic Industries Association (EIA). RS485 standard supports up to 32 devices in its serial communication network. The RS485 network must be designed as one line with multiple drops, not as a star. RS232 has a separate communication line for transmitting and receiving which-with a well written protocol-allows higher effective data rates at the same bit rate than the other interfaces.