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Modbus TCP nomenclature is the same as for the Modbus over Serial line protocol, as any device which send out a Modbus command, is the 'client' and the response comes from a 'server'. [29] The ADU for Modbus TCP is officially called Modbus TCP/IP ADU by the Modbus organization [30] and is also called Modbus TCP frame by other parties. [3]
Modbus PEMEX; Modbus Plus; Modbus RTU or ASCII or TCP; MPI – Multi Point Interface; OSGP – The Open Smart Grid Protocol, a widely use protocol for smart grid devices built on ISO/IEC 14908.1; OpenADR – Open Automated Demand Response; protocol to manage electricity consuming/controlling devices
A telegram (message frame) consists of 4-bit user data. The master communicates with the participants with a serial transmission protocol. Each subscriber is assigned an address by an addressing device or via the master. A maximum of 31 (standard devices) or 62 (advanced devices) nodes can be connected.
While IEEE 488.2 provided a device-independent syntax, there was still no standard for instrument-specific commands. Commands to control the same class of instrument, e.g., multimeters, would vary between manufacturers and even models. The United States Air Force, [9] and later Hewlett-Packard, recognized this problem.
Before a register access, PHY devices generally require a preamble of 32 ones to be sent by the MAC on the MDIO line. The access consists of 16 control bits, followed by 16 data bits. The control bits consist of 2 start bits, 2 access type bits (read or write), the PHY address (5 bits), the register address (5 bits), and 2 "turnaround" bits.
Modbus also uses a master device to initiate connection requests to slave devices. An edge-triggered flip-flop can be created by arranging two gated latches in a master–slave configuration. It is so named because the master latch controls the slave latch's value and forces the slave latch to hold its value, as the slave latch always copies ...
NXP devices have a higher power set of electrical characteristics than SMBus 1.0. The main difference is the current sink capability with V OL = 0.4 V. SMBus low power = 350 μA; SMBus high power = 4 mA; I²C-bus = 3 mA; SMBus ‘high power’ devices and I²C-bus devices will work together if the pull-up resistor is sized for 3 mA.
The OPC Data Access Specification is the first of a group of specifications known as the OPC Classic Specifications. [1]OPC Data Access is a group of client–server standards that provides specifications for communicating real-time data from data acquisition devices such as PLCs to display and interface devices like Human–Machine Interfaces (HMI), SCADA systems [2] and also ERP/MES systems. [3]