Demultiplexer
| Library: | Plexers |
| Introduced: | 2.0 Beta 11 |
| Appearance: |
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Behavior
An output will match the west edge input if its number matches the value currently received through the select input on the south edge; otherwise, its value will be either all-zeroes or all-floating, depending on the value of the Three-State? attribut. If the select input contains any floating (U) bits, then all outputs are floating (U). If the select input contains the value error(E), then all outputs are error error(E). I find it useful to think of a demultiplexer as analogous to a railroad switch, controlled by the select input.
(Incidentally, some authorities spell this demultiplexor, but demultiplexer is the predominant spelling.)
Pins (assuming component faces east, select is bottom/left)
- West edge:
- Input that receives the value to be routed to one of the outputs of the eastern edge. Bit width matches Data Bits attribute.
- East edge:
-
A variable number of outputs they are numbered starting with 0 in the north. The number of entries is determined by the 2Select Bits attribute.
Bit width matches Data Bits attribute. - South edge, left side:
- input Enable: When 0, all outputs consist of all floating bits (U), regardless of the data and select inputs. Bit width 1
- South edge, right side indicated by gray circle:
- Input Select: The value of this input determines to which output on the east edge to route the value received on the west edge. Bit width matches Select Bits attribute.
Attributes
When the component is selected or being added, the digits 1 through 5 alter its Select Bits attribute, Alt-0 through Alt-9 alter its Data Bits attribute, and the arrow keys alter its Facing attribute.
- Facing
- The direction of the component, specifying which side has the outputs.
- Select Location
- The location of the select and enable lines relative to the component.
- Select Bits
- The bit width of the component's select input on its south edge. The number of outputs for the demultiplexer will be 2selectBits.
- Data Bits
- The bit width of the data being routed through the demultiplexer.
- Three-state?
- Specifies whether the unselected outputs should be floating(U) (Yes) or zero(0) (No).
- Disabled Output
- Specifies what each bit of the outputs should be when the component is disabled (i.e., when the enable pin is 0). Options include zero and floating; in the latter case, the outputs are effectively disconnected from any other ports.
- Include Enable?
- The component has an enable input when this attribute is yes. The attribute is primarily for supporting circuits built using older versions of Logisim that did not provide an enable input.
Poke Tool Behavior
None.
Text Tool Behavior
None.
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