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September 2015 • The PCB Design Magazine 51 sample of nets for, say, data, address, clocks and strobes to define the layout design rules. These rules are embedded in the schematic via the constraints manager, and they will then flow through to the layout database with forward an- notation. Constraints are maintained through a common database that is consistent and in an easy-to-use spreadsheet interface. There is no need to learn an obscure program language to create complex constraints as in other tools. Consequently, any unsightly waveforms (under/overshoots) can be dealt with by the Termination Wizard, which automatically se- lects the correct type and value of termination based on the IBIS model characteristics and that of the transmission line. It really makes signal integrity too easy. And providing engineering intent to the layout designer at the schematic level imparts an error-free process. Integration of the schematic and PCB is through a common database, so there are no netlist errors to contend with. Simply package and begin layout. The first thing I noticed when beyond design I entered the PCB environment is the smooth panning of the graphics. Once I got used to the correct mouse buttons to use, panning and zooming were a breeze—amazingly fast and smooth. Another highlight is that if you hap- pen to move a previously routed component, it just re-routes the connections for you. Obvi- ously this has limitations, such as with large BGAs, but most ICs can easily be moved to rear- range the placement and routing. Moving vias and routed traces is also a breeze. Simply click and drag with seemingly limitless shove capa- bilities, and even differential pairs are pushed and shoved whilst maintaining their design constraints. Additionally, the use of mouse strokes for quick execution of commands, rather than hot- keys, is a pleasant flashback from my UNIX past. Basically, you can define stroke patterns to rep- resent any command so that you just keep mov- ing the mouse rather than having to refocus on the keyboard. This makes executing commands very fast. Figure 3: 3D view of the PCB. ToP GEAR: PADS PRoFESSIoNAl RoAD TEST

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