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Virtual instrument software architecture (VISA) is a widely used application programming interface (API) in the test and measurement (T&M) industry for communicating with instruments from a computer.
Each layer in the OSI model has well-defined functions, and the methods of each layer communicate and interact with those of the layers immediately above and below as appropriate. The Internet protocol suite as defined in RFC 1122 and RFC 1123 is a model of networking developed contemporarily to the OSI model, and was funded primarily by the U ...
First released in 1990, [3] [6] SCPI originated as an additional layer for IEEE-488. IEEE-488.1 specified the physical and electrical bus, and IEEE-488.2 specified protocol and data format, but neither specified instrument commands. Different manufacturers, and even different models, of the same type of instrument would use different command sets.
The OSI protocol stack is structured into seven conceptual layers. The layers form a hierarchy of functionality starting with the physical hardware components to the user interfaces at the software application level. Each layer receives information from the layer above, processes it and passes it down to the next layer.
Keithley Instruments is a measurement and instrument company headquartered in Solon, Ohio, that develops, manufactures, markets, and sells data acquisition products, as well as complete systems for high-volume production and assembly testing.
The physical layer contribution to RapidIO packets is a 2-byte header at the beginning of each packet that includes the ackID and physical priority, and a final 2-byte CRC value to check the integrity of the packet. Packets larger than 80 bytes also have an intermediate CRC after the first 80 bytes.
The HART Communication Protocol (Highway Addressable Remote Transducer) is a hybrid analog+digital industrial automation open protocol. Its most notable advantage is that it can communicate over legacy 4–20 mA analog instrumentation current loops, sharing the pair of wires used by the analog-only host systems.
I/O virtualization environments are created by abstracting the upper layer protocols from the physical connections. [ 1 ] The technology enables one physical adapter card to appear as multiple virtual network interface cards (vNICs) and virtual host bus adapters (vHBAs). [ 2 ]