EEVblog Electronics Community Forum
Electronics => PCB/EDA/CAD => KiCad => Topic started by: Dan Moos on August 06, 2017, 07:10:58 pm
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As I think I understand it, the only real difference between a global and a hierarchical label is that a hierarchical label needs a corresponding pin in each sheet to make it available to said sheets, whereas, global labels act as if all the sheets are one big sheet connectivity-wise.
My question is, whats the point? I can't see why I wouldn't just use global labels, and save a step? I feel like I'm missing something.
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Because you can have several copies of the same sheet, each will have different connections if using hierarchical connections. There is an example in http://docs.kicad-pcb.org/stable/en/eeschema.html#complex-hierarchy (http://docs.kicad-pcb.org/stable/en/eeschema.html#complex-hierarchy)
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Hierarchical comes in very handy if your reusing blocks of a schematic in other projects, you just append the piece as a hierarchical sheet, wire up the pins to your top level block and off you go.
Global can be hard to find at times, but there are things like local voltage rails where i am happy to just call them global, but i get cautious just bulk naming on global as in bigger projects it can be very easy to end up reusing the same name and not realising until your final board reviews.
It can also help make your top level schematic act like your project mud map, a hierarchical bus between 2 sub sheets for your LCD data, etc, the tools are there to be used as you see fit.