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gnucap:user:schematic_geometry [2024/12/03 09:12] (current) felixs created |
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| + | ====== Schematic geometry ====== | ||
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| + | Verilog-AMS defines hierarchical parameters ''$xposition'' and ''$yposition'' as well as ''$angle'' to express physical location and orientation as on a wafer or PCB. According to the LRM, ''$angle'' is supposed to mean "counter-clockwise". | ||
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| + | Our interpretation of counter-clockwise follows when choosing the x axis pointing to the right, and the y axis pointing upwards. Now a 90 degree rotation moves the x axis to the y axis, in other words ''(x,y)=(1,0)'' to ''(0,1)''. Equivalently, the y axis may be thought of as the imaginary axis in the complex plane. Then, rotation by 2\pi\phi corresponds to multiplication by exp(2\pi\phi * i), with the imaginary unit i. | ||
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| + | This seems relevant when moving on to schematics. Since Verilog-AMS is governed by physical semantics, we retain this choice of angle and coordinates also for schematic drawings, even though other coordinate systems are in common use. | ||
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| + | If you prefer a y axis pointing downwards, you may use a flipped coordinate system locally, as within the body of the following module. | ||
| + | As expected, any uses of ''angle'' inside the body will be applied before the final vflip. | ||
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| + | <code> | ||
| + | (* S0_vflip=-1 *) | ||
| + | module upside_down_module(); | ||
| + | [..] | ||
| + | endmodule | ||
| + | </code> | ||
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| + | ====== Schematic Units ====== | ||
| + | (todo) | ||