344:, the polling device or process queries each element on a list in a fixed sequence. Because it waits for a response from each element, a timing mechanism is necessary to prevent lock-ups caused by non-responding elements. Roll call polling can be inefficient if the overhead for the polling messages is high, there are numerous elements to be polled in each polling cycle and only a few elements are active.
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device until it is ready, at which point the device is accessed. In other words, the computer waits until the device is ready. Polling also refers to the situation where a device is repeatedly checked for readiness, and if it is not, the computer returns to a different task. Although not as wasteful
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generated by devices or processes to indicate that they need attention, want to communicate, etc. Although polling can be very simple, in many situations (e.g., multitasking operating systems) it is more efficient to use interrupts because it can reduce processor usage and/or bandwidth consumption.
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polling arrangement whereby the central computer sends message (called polling message) to a specific terminal on the outgoing line. All terminals listen to the outgoing line, but only the terminal that is polled replies by sending any information that it has ready for transmission on the incoming
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Polling can be employed in various computing contexts in order to control the execution or transmission sequence of the elements involved. For example, in multitasking operating systems, polling can be used to allocate processor time and other resources to the various competing processes.
295:. If the host is sending output, it sets the write bit and writes a byte into the data-out register. If the host is receiving input, it reads the controller-written data from the data-in register, and sets the read bit to 0 as the next command.
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In networks, polling is used to determine which nodes want to access the network. It is also used by routing protocols to retrieve routing information, as is the case with EGP (
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Polling has the disadvantage that if there are too many devices to check, the time required to poll them can exceed the time available to service the I/O device.
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Once the operations are over, the controller clears the command-ready bit, clears the error bit to show the operation was successful, and clears the busy bit.
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is connected via a parallel port, the computer waits until the printer has received the next character. These processes can be as minute as only reading
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operations on the device. If the read bit is set, data from the device is loaded into the data-in register for the host to read.
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This article is about the computer science term. For the mathematical model, see
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share a single communication line to and from the computer), the system uses a
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Polling is the process where the computer or controlling device waits for an
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as a synchronous activity. Polling is most often used in terms of
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of the controller until it becomes clear (with a value of 0).
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When clear, the host writes the command into the command
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277:Polling can be described in the following steps:
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246:Polling is often intimately involved with very
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131:Learn how and when to remove this message
365:An alternative to polling is the use of
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208:' polling. In this situation, when an
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69:adding citations to reliable sources
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121:January 2015
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18:Poll message
437:Bit banging
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188:Description
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478:References
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264:flip flops
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273:Algorithm
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