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Modbus or MODBUS is a client/server data communications protocol in the application layer. [1] It was originally designed for use with programmable logic controllers (PLCs), [2] but has become a de facto standard communication protocol for communication between industrial electronic devices in a wide range of buses and networks.
The DNP Protocol has time stamped variants of all point data objects so that even with infrequent RTU polling, it is still possible to receive enough data to reconstruct a sequence of events of what happened in between the polls. The DNP3 protocol has a substantial library of common point-oriented objects.
A remote terminal unit (RTU) is a microprocessor-controlled electronic device that interfaces objects in the physical world to a distributed control system or SCADA (supervisory control and data acquisition) system by transmitting telemetry data to a master system, and by using messages from the master supervisory system to control connected objects. [1]
Many are designed to send information only when the master station polls the RTU. Typical legacy SCADA protocols include Modbus RTU, RP-570, Profibus and Conitel. These communication protocols, with the exception of Modbus (Modbus has been made open by Schneider Electric), are all SCADA-vendor specific but are widely adopted and used.
A male D-subminiature connector used for an RS-232 serial port on an IBM PC compatible computer along with the serial port symbol. A serial port is a serial communication interface through which information transfers in or out sequentially one bit at a time. [1]
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. DH 485 is a proprietary communications protocol used by Allen-Bradley in their line of industrial control units.
Here we find the solutions Ethernet/IP, three versions of PROFINET IO - the classes A, B, and C - and the solutions of P-NET, [28] Vnet/IP [29] TCnet, [30] EtherCAT, Ethernet POWERLINK, Ethernet for Plant Automation (EPA), and also the MODBUS with a new Real-Time Publish-Subscribe MODBUS-RTPS and the legacy profile MODBUS-TCP.
Software flow control is a method of flow control used in computer data links, especially RS-232 serial.It uses special codes, transmitted in-band, over the primary communications channel.