# Splitter

Library: | Wiring
Introduced: | 2.0 Beta 1 (in Base library, moved to Wiring in 2.7.0)
Appearance: |

## Behavior

The splitter creates a correspondence between a multi-bit value and several separate subsets of those bits. Despite its name, it can either split a multi-bit value into component parts, or it can combine component parts into a multi-bit value - or indeed it can do both at once. A more complete description of splitters is found in the `Splitters' section of the User's Guide.

Logisim treats splitters specially when propagating values within a circuit: Whereas all other components have a computed delay for purposes of simulating their behavior, values propagate through splitters (as well as wires) instantaneously.

Note: The term splitter is a non-standard term, which is unique to Logisim as far as I know. I am unaware of any standard term for such a concept; the only term I have heard used is bus ripper, but this term is unnecessarily violent for my tastes.

## Pins

To distinguish the several connecting points for a splitter, we refer to the single connecting point one side as its combined end, and we refer to the multiple connecting points on the other side as its split ends.

Combined end (input/output bit width matches Bit Width In attribute)
  A value holding all of the bits traveling through the splitter.
Split ends (input/output, bit width computed based on Bit x attributes)
  The number of split ends is specified in the Fan Out attribute, and each split end has an index that is at least 0 and less than the Fan Out attribute. For each split end, all bits for which Bit x refers to its index travels through that split end; the order of these bits is the same as their order within the combined end.

## Attributes

When the component is selected or being added, the digits '0' through '9' alter its Fan Out attribute, Alt-0 through Alt-9 alter both the Fan Out and Bit Width In attributes, and the arrow keys alter its Facing attribute.

Facing

  The location of the split ends relative to the combined end.

Fan Out

  The number of split ends.

Bit Width In

  The bit width of the combined end.

Appearance

  Supports different ways of depicting the splitter in the circuit. The Left-handed option (the default) draws a spine going left from the combined end, with a labeled line coming from the spine for each split end. The Right-handed option is the same except the spine goes right (if you're facing according to the Facing attribute). The Centered option centers the spine so it goes in roughly equal directions left and right. And the Legacy option draws diagonal lines to each split end, without labels; this option is primarily for compatibility with versions older than 2.7.0, when this was the only option for splitter appearance.

Bit x

  The index of the split end to which bit x of the combined end corresponds. The split ends are indexed starting from 0 at the top (for a splitter facing east or west) or from 0 at the left/west (for a splitter facing north or south). A bit can be specified to correspond to none of the split ends. There is no way for a bit to correspond to multiple split ends.

  Sometimes you can avoid twiddling each individual Bit x attribute by bringing up the pop-up menu for a splitter (usually by right-clicking or control-clicking it). The pop-up menu includes options labeled Distribute Ascending and Distribute Descending. The Distribute Ascending option distributes the bits so that each split end receives the same number of bits, starting from end 0. (If the number of split ends doesn't divide exactly into the number of bits, then the bits are distributed as evenly as possible.) Distribute Descending does the same but starts from the highest-numbered end.

## Poke Tool Behavior

None.

## Text Tool Behavior

None.

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