Demultiplexing and Dispatching Handles for Synchronous Events. The key participants in the Reactor pattern include the fol-lowing.![]() The Reactor An Object-Oriented Wrapper for Event-Driven Port Monitoring and Service Demultiplexing (Part 1 of 2) Douglas C. Schmidt [email protected]. Data- flow based speculative parallelization of methods in sequential programs. Bib. Te. X@INPROCEEDINGS. ![]() Multiplexer - Wikipedia, the free encyclopedia. This article is about electronic switching. For telecommunications, see multiplexing. It can be equated to a controlled switch. Like a multiplexer, it can be equated to a controlled switch. In electronics, a multiplexer (or mux) is a device that selects one of several analog or digital input signals and forwards the selected input into a single line. Multiplexers can also be used to implement Boolean functions of multiple variables. An electronic multiplexer makes it possible for several signals to share one device or resource, for example one A/D converter or one communication line, instead of having one device per input signal. Conversely, a demultiplexer (or demux) is a device taking a single input signal and selecting one of many data- output- lines, which is connected to the single input. A multiplexer is often used with a complementary demultiplexer on the receiving end. On the receiving side, a demultiplexer splits the single data stream into the original multiple signals. One use for multiplexers is cost saving by connecting a multiplexer and a demultiplexer together over a single channel (by connecting the multiplexer's single output to the demultiplexer's single input). The image to the right demonstrates this. In this case, the cost of implementing separate channels for each data source is higher than the cost and inconvenience of providing the multiplexing/demultiplexing functions. At the receiving end of the data link a complementary demultiplexer is normally required to break single data stream back down into the original streams. In some cases, the far end system may have more functionality than a simple demultiplexer and so, while the demultiplexing still exists logically, it may never actually happen physically. This would be typical where a multiplexer serves a number of IP network users and then feeds directly into a router which immediately reads the content of the entire link into its routing processor and then does the demultiplexing in memory from where it will be converted directly into IP sections. Often, a multiplexer and demultiplexer are combined together into a single piece of equipment, which is usually referred to simply as a . ![]() ![]() ![]()
Both pieces of equipment are needed at both ends of a transmission link because most communications systems transmit in both directions. In analog circuit design, a multiplexer is a special type of analog switch that connects one signal selected from several inputs to a single output. Digital multiplexers. In the case of a 2- to- 1 multiplexer, a logic value of 0 would connect I0. In larger multiplexers, the number of selector pins is equal to . The binary value expressed on these selector pins determines the selected input pin. A 2- to- 1 multiplexer has a boolean equation where A. A straightforward realization of this 2- to- 1 multiplexer would need 2 AND gates, an OR gate, and a NOT gate. While this is mathematically correct, it should be noted that a direct physical implementation would be prone to race conditions that require additional gates to suppress. Other common sizes are 4- to- 1, 8- to- 1, and 1. Since digital logic uses binary values, powers of 2 are used (4, 8, 1. The boolean equation for a 4- to- 1 multiplexer is: Z=(A. For example, an 8- to- 1 multiplexer can be made with two 4- to- 1 and one 2- to- 1 multiplexers. The two 4- to- 1 multiplexer outputs are fed into the 2- to- 1 with the selector pins on the 4- to- 1's put in parallel giving a total number of selector inputs to 3, which is equivalent to an 8- to- 1. List of ICs which provide multiplexing. They forward the data input to one of the outputs depending on the values of the selection inputs. Demultiplexers are sometimes convenient for designing general purpose logic, because if the demultiplexer's input is always true, the demultiplexer acts as a decoder. This means that any function of the selection bits can be constructed by logically OR- ing the correct set of outputs. If X is the input and S is the selector, and A and B are the outputs: A=(X. Any Boolean function of n variables and one result can be implemented with a multiplexer with n selector inputs. The variables are connected to the selector inputs, and the function result, 0 or 1, for each possible combination of selector inputs is connected to the corresponding data input. This is especially useful in situations when cost is a factor, for modularity, and for ease of modification. If one of the variables (for example, D) is also available inverted, a multiplexer with n- 1 selector inputs is sufficient; the data inputs are connected to 0, 1, D, or ~D, according to the desired output for each combination of the selector inputs.
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