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Toporouter (Anthony Blake's open-source router in PCB of the gEDA suite).TopoR (a Windows-based autorouter, also used in Eremex's Delta Design).FreeStyle Router (aka SpeedWay, a DOS-based autorouter for P-CAD).Specctra (aka Allegro PCB Router) (gridless since version 10).Bloodhound router ( CADSTAR by Racal-Redac / Zuken).
Nets not attached to parts pcad 2006 software#
Modern PCB design software also typically provides "autorouters" that route all remaining unrouted connections without human intervention. Some more advanced interactive routers have "push and shove" (aka "shove-aside" or "automoving") features in an interactive router the EDA tool pushes other nets out of the way, if possible, in order to place a new wire where the drafter wants it and still avoid violating DRC. Modern PCB design software typically provides "interactive routers"-the drafter selects a pad and clicks a few places to give the EDA tool an idea of where to go, and the EDA tool tries to place wires as close to that path as possible without violating design rule checking (DRC). The earliest types of EDA routers were "manual routers"-the drafter clicked a mouse on the endpoint of each line segment of each net. Both surface mount and through-hole components have been used. The board is double sided, with through-hole plating, green solder resist and a white legend. Particular difficulties ensue if the rules are not simple multiples of each other, and when vias must traverse between layers with different rules.Ī PCB as a design on a computer (left) and realized as a board assembly populated with components (right). This introduces many additional complications not faced by routers for other applications such as printed circuit board or multi-chip module design. For example, the allowed width and spacing on the lower layers may be four or more times smaller than the allowed widths and spacings on the upper layers. Instead, almost all routing is based on heuristics which try to find a solution that is good enough.ĭesign rules sometimes vary considerably from layer to layer. Routers therefore seldom attempt to find an optimum result. Variants of channel routing have also been shown to be NP-complete, as well as routing which reduces crosstalk, number of vias, and so on. The simplest routing problem, called the Steiner tree problem, of finding the shortest route for one net in one layer with no obstacles and no design rules is NP-hard if all angles are allowed and NP-complete if only horizontal and vertical wires are allowed. This long list of often conflicting objectives is what makes routing extremely difficult.Īlmost every problem associated with routing is known to be intractable. In addition, to correctly connect the nets, routers may also be expected to make sure the design meets timing, has no crosstalk problems, meets any metal density requirements, does not suffer from antenna effects, and so on. A router can fail by not connecting terminals that should be connected (an open), by mistakenly connecting two terminals that should not be connected (a short), or by creating a design rule violation. The primary task of the router is to create geometries such that all terminals assigned to the same net are connected, no terminals assigned to different nets are connected, and all design rules are obeyed. Each of these polygons are associated with a net, usually by name or number. They are given some pre-existing polygons consisting of pins (also called terminals) on cells, and optionally some pre-existing wiring called preroutes. Together, the placement and routing steps of IC design are known as place and route. After placement, the routing step adds wires needed to properly connect the placed components while obeying all design rules for the IC. It builds on a preceding step, called placement, which determines the location of each active element of an IC or component on a PCB. In electronic design, wire routing, commonly called simply routing, is a step in the design of printed circuit boards (PCBs) and integrated circuits (ICs). For other kinds of routing, see routing (disambiguation). This article is about designing integrated circuits, as part of electronic design automation.