Place and route

Place and route is a stage in the design of printed circuit boards, integrated circuits, and field-programmable gate arrays. As implied by the name, it is composed of two steps, placement and routing. The first step, placement, involves deciding where to place all electronic components, circuitry, and logic elements in a generally limited amount of space. This is followed by routing, which decides the exact design of all the wires needed to connect the placed components. This step must implement all the desired connections while following the rules and limitations of the manufacturing process.

Place and route is used in several contexts:

These processes are similar at a high level, but the actual details are very different. With the large sizes of modern designs, this operation is usually performed by electronic design automation (EDA) tools.

In all these contexts, the final result when placing and routing is finished is the layout, a geometric description of the location and rotation of each part, and the exact path of each wire connecting them.

Occasionally some people call the entire place-and-route process layout.

The design of a printed circuit board comes after the creation of a schematic and generation of a netlist. The generated netlist is then read into a layout tool and associated with part footprints from a library. Placing and routing can now start.

Placing and routing is generally done in two steps. Placing the components comes first, then routing the connections between the components. The placement of components is not absolute during the routing phase, as it may still be changed by moving and rotating, especially with designs using more complex components such as FPGAs or microprocessors. Their large number of signals, and their signal integrity needs may require optimization of the placement.

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