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42 The PCB Design Magazine • August 2014 This article is part one of a three-part series that will discuss a new routing tool that allows PCB designers to "sketch" the routing of traces and then routes along the path of the sketch (Figure 1). The articles discuss the core elements of effective PCB routing—control, quality, and performance—and how the sketch routing en- vironment empowers the designer to succeed with each of these elements. In the past, one of these three was always missing from routing capability; yet without all three, the functionality falls short of being the truly useful and desirable solution that design- ers want. This first article describes the kind of control over routing that is expected. As designers, we often envision topology forms in our minds as we organize the rough component placement and as we refine it with- in the context of each particular design. Of course, there are exceptions that make this vi- sualization difficult, such as emulation or net- work boards where nearly every BGA I/O is con- nected to every other of the 8, 16, 32 or more BGAs on the design. And to our horror, the net- line display is so dense that it appears as a solid color. With those types of designs, something be- yond the normal approach is needed. Normal designs feature an organization of ASICs and/ or FPGAs with interfaces, various functional cir- cuits, and power supplies, which are grouped and positioned during placement. With that so-called "normal" design, a plan, a flow of the routing, and a solution to the in- terconnect complexity forms in our imagina- tion, which is coupled with the graphic feed- back of netlines, classlines, coloring, and filter- ing. Designers want tools that enable control of the actual routing so that it matches this vision. The control needed is three-fold: location, constraints, and route style. This is what a de- signer needs to manage for successful routing of the design as intended. This control needs to be easily applied without abusive setup ma- neuvers. Location Location is not only related to the layer(s) where the routes are to be placed, but also the path or channel where the traces run. River routing is a term that applies to much of to- day's routing, because there is a desire for the by Charles Pfeil MenTOR gRAPhiCs CORP. SKETCH RoUTING Part 1: Taking Control column Figure 1: With sketch routing, the designer looks at the netlines and then draws a sketch (left), directing the router as to how they should be routed. On the right, the completed routing is shown.

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