Question about Propeller Object Libraries for Scematic and PCB layout

Greg LaPolla

I have been reading and asking a lot of questions in these forums. One thing I notice is that everyone recommends using caps across VSS/VDD, however most object libs for layout software I have found for the Prop always has the VSS/VDD pins hidden and they auto connect when you Populate the PCB part of the layout, Why is this? or am I missing something ?

Leon

Most PCB packages allow the supply pins (and any other pins) to be hidden on the schematic, although they are actually connected to nets. It reduces clutter and makes the schematic easier to follow. I don't bother with simple chips like the Propeller, and include them in the schematic symbol, but it can be useful with logic chips with multiple gates, and op-amps. With complex chips with dozens of supply and ground pins I generally have a separate gate in the symbol with those connections on it, and put it on its own page, with the decoupling capacitors.

Leon

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Post Edited (Leon) : 6/22/2009 4:46:16 PM GMT

Chris Savage

There are several schools of thought on this, but because it is important for the Propeller to have all Vdd/Vss lines connected, I tend to make my symbols chip-centric and show all the connections, including power/ground, even when there are multiple power/ground connections. There’s no point short-cutting on something important. I hope this helps. Take care.

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Chris Savage
Parallax Engineering