Unidirectional port

Unidirectional ports fnnction in a single direction, nsnally retrieving data from a physical instrnment port into the data management system. 

With unidirectional ports the instrnment leads the processing of data, and the data management system waits for information from the instrnment. Unidirectional ports do not attempt to control the instrnment software. The most sophisticated solution is to connect directly to an instrnment nsing a bidirectional port. In this case work lists or single measnrement orders are compiled by the data management software during the rontine workflow and measnrements are triggered directly. 

The first cyclative cleavage of a small molecule was Crowley and Rapo-port s study41 of intramolecular Dieckmann condensations on solid phase (Fig. 13), which was complicated by the reversible nature of the cyclization. Despite the unique opportunities afforded by C-C rather than C-X bond formation during cleavage, there are few examples from the combinatorial age. A modern version of the Claisen-type condensation by Kulkarni and Ganesan42 uses a strongly acidic active methylene group to ensure unidirectional cyclization, and furnishes tetramic acids with three points of diversity. 

As their names suggest, terminal servers and print servers support the use of terminals and printers on networks. They support modems and other devices as well. The primary difference between them is that terminal servers are bidirectional devices while print servers have been unidirectional devices, at least as far as data transmissions are concerned. Unlike transceivers, repeaters, or port multipliers, terminal servers and print servers are intelligent devices which have their own network addresses and perform more than just a physical connection or signal forwarding function. 

Each bus type has a set of lines that are used to allow the CPU to send instructions to the devices installed in the bus s slots. Each device is given its own unique communication line to the CPU. These lines are called input/output (I/O) addresses and they function a lot like unidirectional mailboxes. If you want to send an invitation for people to come to a party, you write a message and address it to the mailbox of the person you want to invite. When the person receives the message, they read it and return some information, perhaps via some other method (such as a phone call). The I/O addresses (also called I/O ports or hardware ports) work in a similar fashion. When the CPU wants a device to do something, it sends a signal to a particular I/O address telling the device what to do. The device then responds via the data bus or DMA channels. 

It is imperative that the interface between the computer-based control system and the environment it is controlling is well defined and appropriately constrained. This is one of the attractive features of the time-triggered architecture and is equally important for the event-triggered (ET) approach. An ET interface consists of state data and event ports. State data are written by one side of the interface and read by the other. Concurrent reads and writes are noninterfering. The temporal validity of the data is known (or can be ascertained) by the reading activity. This may require an associated time-stamp but may alternatively be a static property that can be validated prior to execution. An event port allows an event to pass through the interface. It is unidirectional. The occurrence of an event at the system interface will result in a computational process being released for execution. The effect of an output event into the computer system s environment cannot be defined it is application-specific. 

We have defined an ET interface that allows state data and events ports to be used. All communication through an interface is unidirectional. Such interfaces link the computer system to its environment and are used internally... 

With the producer-consumer model no surrogate processes are needed as only data and events are been communicated. A single unidirectional message send facility is all that is required. The role of the communication system is to transfer state data between subsystem interfaces and to transport events from one subsystem to another. At the receiver, data need to be placed in the correct interface object (conceptually via dual port memory between the communication controller and the host processor) and events need to invoke application processes (typically via an interrupt mechanism). 

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