Hierarchy and Datapaths
MUXes in a Datapath
How control signals select the data path into an ALU, a write-back destination, or another datapath connection.
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MUXes are the routing points of a datapath. A MUX can choose which source feeds an ALU input, which result is written back to storage, or which value reaches an output.
The MUX's input and output wires carry data. Its select wire is control: it represents the controller's decision about the route for this operation. This separation lets one ALU serve operations that use different kinds of operands without duplicating the ALU.
When reading a datapath, identify the MUX first, then list its possible sources, and finally find the control signal that selects between them.