Place and route (also called PnR or P&R) 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:
- Printed circuit boards, during which components are graphically placed on the board and the wires drawn between them
- Integrated circuits, during which a layout of a larger block of the circuit or the whole circuit is created from layouts of smaller sub-blocks
- FPGAs, during which logic elements are placed and interconnected on the grid of the FPGA
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".
