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:

*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.

Printed Circuit Board

Place and Route of a printed circuit board generally comes after the creation of a schematic or generation of a netlist. The generated netlist is then read in to a layout tool, and associated with part footprints from a library. After this step is generally place and route.

Place and Route is generally done in two steps. Placing the components comes first, then routing the connections between the components. Though the component placement is not absolute during the routing phase of the design process. It may be tweaked by rotating or moving the components. This is especially true when using more complex components such as FPGAs or Microprocessors. Their large amounts of signals, and their signal integrity needs may make the original placement not optimal.cite web |url = http://pcdandf.com/cms/content/view/4345/95/ |title = FPGA/PCB Co-Design Increases Fabrication Yields |accessdate = 2008-07-24 |publisher=Printed Circuit Design and Fabrication]

Field Programmable Gate Array

The process of place and route for an FPGA is generally not performed by a person, but uses a tool provided by the FPGA Vendor or another software manufacturer. The need for software tools is because of the complexity of the circuitry within the FPGA, and the function the designer wishes to perform. The FPGA is designed using logic diagrams containing both digital logic and Very High Speed Integrated Circuits Hardware Description Language (VHDL), or Verilog. These will then be put through an automated place and route procedure to generate a pinout, which will be used to interface with the parts outside of the FPGA.

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