The standard is jointly published by the Telecommunications Industry Association and Electronic Industries Alliance (TIA/EIA). Electronic Industries Association (1983). Electrical Characteristics of Generators and Receivers for Use in Balanced Multipoint Systems. For an off, mark or logic 1 state, the driver's A terminal is negative relative to the B terminal. For an on, space or logic 0 state, the driver's A terminal is positive relative to the B terminal. Because a mark (logic 1) condition is traditionally represented (e.g. in RS-232) with a negative voltage and space (logic 0) represented with a positive one, A may be considered the non-inverting signal and B as inverting. Line A voltage, implying A, the green wire, is indeed connected to the driver inverting signal, as seen in a whitepaper. 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. Care must be taken when using A/B naming. 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.
Failure to stay within this range will result in, at best, signal corruption, and, at worst, damage to connected devices. 12 V, i.e. ±7 V on top of the 0-5 V signal range. RS-485 signals are used in a wide range of computer and automation systems. Converters between RS-485 and RS-232 are available to allow a personal computer to communicate with remote devices. In a computer system, SCSI-2 and SCSI-3 may use this specification to implement the physical layer for data transmission between a controller and a disk drive. Circuits may be terminated on screw terminals, D-subminiature connectors, or other types of connectors. The two values provide a sufficient margin for a reliable data transmission even under severe signal degradation across the cable and connectors. PC environment. 8P8C modular connectors are used in this case. This robustness is the main reason why RS-485 is well suited for long-distance networking in noisy environment.
The equipment located along a set of RS-485 wires are interchangeably called nodes, stations or devices. This way, the lines will be biased to known voltages and nodes will not interpret the noise from undriven lines as actual data; without biasing resistors, the data lines float in such a way that electrical noise sensitivity is greatest when all device stations are silent or unpowered. SC, G or reference, what is rs485 cable the common signal reference ground used by the receiver to measure the A and B voltages. RS-485 is used as the physical layer underlying many standard and proprietary automation protocols used to implement industrial control systems, including the most common versions of Modbus and Profibus. The standard does not discuss cable shielding but makes some recommendations on preferred methods of interconnecting the signal reference common and equipment case grounds. It also defines three generator interface points (signal lines); A, B and C. The data is transmitted on A and B. C is a ground reference. The termination also includes pull up and pull down resistors to establish bias for each data wire for the case when the lines are not being driven by any device.
Ideally, the two ends of the cable will have a termination resistor connected across the two wires. This allows RS-485 to implement linear bus topologies using only two wires. If A is negative with respect to B, the state is binary 1. The reversed polarity (A positive with respect to B) is binary 0. The standard does not assign any logic function to the two states. This section also defines the logic states 1 (off) and 0 (on), by the polarity between A and B terminals. Section 4 defines the electrical characteristics of the generator (transmitter or driver), receiver, transceiver, and system. RS-422 and RS-485 Standards Overview and System Configurations, Application Report (pdf). It does not specify or recommend any communications protocol; Other standards define the protocols for communication over an RS-485 link. The EIA once labeled all its standards with the prefix "RS" (Recommended Standard), but the EIA-TIA officially replaced "RS" with "EIA/TIA" to help identify the origin of its standards. Star and ring topologies are not recommended because of signal reflections or excessively low or high termination impedance. The recommended arrangement of the wires is as a connected series of point-to-point (multidropped) nodes, i.e. a line or bus, not a star, ring, or multiply connected network.
Since RS-485 is a Multi-point Specification
by Christena Keys (2024-07-28)
The standard is jointly published by the Telecommunications Industry Association and Electronic Industries Alliance (TIA/EIA). Electronic Industries Association (1983). Electrical Characteristics of Generators and Receivers for Use in Balanced Multipoint Systems. For an off, mark or logic 1 state, the driver's A terminal is negative relative to the B terminal. For an on, space or logic 0 state, the driver's A terminal is positive relative to the B terminal. Because a mark (logic 1) condition is traditionally represented (e.g. in RS-232) with a negative voltage and space (logic 0) represented with a positive one, A may be considered the non-inverting signal and B as inverting. Line A voltage, implying A, the green wire, is indeed connected to the driver inverting signal, as seen in a whitepaper. 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. Care must be taken when using A/B naming. 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.
Failure to stay within this range will result in, at best, signal corruption, and, at worst, damage to connected devices. 12 V, i.e. ±7 V on top of the 0-5 V signal range. RS-485 signals are used in a wide range of computer and automation systems. Converters between RS-485 and RS-232 are available to allow a personal computer to communicate with remote devices. In a computer system, SCSI-2 and SCSI-3 may use this specification to implement the physical layer for data transmission between a controller and a disk drive. Circuits may be terminated on screw terminals, D-subminiature connectors, or other types of connectors. The two values provide a sufficient margin for a reliable data transmission even under severe signal degradation across the cable and connectors. PC environment. 8P8C modular connectors are used in this case. This robustness is the main reason why RS-485 is well suited for long-distance networking in noisy environment.
The equipment located along a set of RS-485 wires are interchangeably called nodes, stations or devices. This way, the lines will be biased to known voltages and nodes will not interpret the noise from undriven lines as actual data; without biasing resistors, the data lines float in such a way that electrical noise sensitivity is greatest when all device stations are silent or unpowered. SC, G or reference, what is rs485 cable the common signal reference ground used by the receiver to measure the A and B voltages. RS-485 is used as the physical layer underlying many standard and proprietary automation protocols used to implement industrial control systems, including the most common versions of Modbus and Profibus. The standard does not discuss cable shielding but makes some recommendations on preferred methods of interconnecting the signal reference common and equipment case grounds. It also defines three generator interface points (signal lines); A, B and C. The data is transmitted on A and B. C is a ground reference. The termination also includes pull up and pull down resistors to establish bias for each data wire for the case when the lines are not being driven by any device.
Ideally, the two ends of the cable will have a termination resistor connected across the two wires. This allows RS-485 to implement linear bus topologies using only two wires. If A is negative with respect to B, the state is binary 1. The reversed polarity (A positive with respect to B) is binary 0. The standard does not assign any logic function to the two states. This section also defines the logic states 1 (off) and 0 (on), by the polarity between A and B terminals. Section 4 defines the electrical characteristics of the generator (transmitter or driver), receiver, transceiver, and system. RS-422 and RS-485 Standards Overview and System Configurations, Application Report (pdf). It does not specify or recommend any communications protocol; Other standards define the protocols for communication over an RS-485 link. The EIA once labeled all its standards with the prefix "RS" (Recommended Standard), but the EIA-TIA officially replaced "RS" with "EIA/TIA" to help identify the origin of its standards. Star and ring topologies are not recommended because of signal reflections or excessively low or high termination impedance. The recommended arrangement of the wires is as a connected series of point-to-point (multidropped) nodes, i.e. a line or bus, not a star, ring, or multiply connected network.