41 lines
1.3 KiB
Markdown
41 lines
1.3 KiB
Markdown
---
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tags: [logic-gates, binary, nand-to-tetris]
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---
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# Multiplexers (MUX) and demultiplexers (DMUX)
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## Multiplexer
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> Multiplexing is the generic term used to describe the operation of sending one
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> or more analogue or digital signals over a common transmission line at
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> different times or speeds.
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A multiplexer selects one of several input signals and forwards ths selected
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input to a single output line.
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We have two inputs (A,B) plus a third input SEL (for "select"). Applying a value
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to SEL toggles the output between A and B.
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Multiplexers can be used to build larger circuits by connecting the output of
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one multiplexer to the input of another. They are often used to implement data
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selection and switching in digital systems
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### Programable gates
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One of the main use cases of multiplexers is to implement programmable gates.
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These are gates where the logic can be switched. For example an ANDMUXOR gate
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uses the SEL value to toggle the operation of a gate between AND and OR for its
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two inputs A and B
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## Demultiplexer
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As the name suggests, a demultiplexer reverses the functionality of a
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multiplexer. It receives a single input and based on the selection of the SEL
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input it channels it to either an A or a B output.
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We can think of it as a distributor of a value into one of several possible
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channels.
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