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gnucap:user:netlist_import_and_export:geda [2025/05/14 05:30] felixs fix port names in example |
gnucap:user:netlist_import_and_export:geda [2025/05/14 05:54] (current) felixs describe net override handling |
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| ==== Connections by attribute ==== | ==== Connections by attribute ==== | ||
| - | A symbol instance that represents a device may have multiple ''net'' attributes with a value like A:B,C,D, see [[https://lepton-eda.github.io/lepton-manual.html/net_003d-attribute-mini_002dHOWTO.html|Lepton manual]]. These are translated to port assignments, and mix with other port assignments. For example | + | === Base case === |
| + | |||
| + | A symbol instance that represents a device may have multiple ''net'' attributes with a value like ''A:B,C,D'', see [[https://lepton-eda.github.io/lepton-manual.html/net_003d-attribute-mini_002dHOWTO.html|Lepton manual]]. | ||
| + | These are translated to port assignments, and mix with other port assignments. For example | ||
| <code>some_device #() my_refdes(.B(A), .C(A), .D(A), [..] .other(n17),[..]);.</code> | <code>some_device #() my_refdes(.B(A), .C(A), .D(A), [..] .other(n17),[..]);.</code> | ||
| + | |||
| + | This reflects that ''A:B,C,D'' is actually a contrived short hand syntax for 3 individual assignments. | ||
| + | |||
| + | === net overrides === | ||
| + | |||
| + | Some situations require untangling identify the intent as illustrated as follows. | ||
| + | For example, the data | ||
| + | |||
| + | net=A:B,C // in the symbol | ||
| + | net=A:X,Y // in the instance | ||
| + | net=B:C // in the instance | ||
| + | net=C:X // in the instance | ||
| + | |||
| + | would be interpreted as | ||
| + | |||
| + | .B(A) .C(A) .X(A) .Y(A) .C(B) .X(C) // untangled assignments in order | ||
| + | .B(A) .C(B) .X(C) .Y(A) // effective port assignment (rightmost wins) | ||
| + | |||
| + | Note that the instance value of "net" does not replace the value assigned in the instance as usual. | ||
| + | |||
| + | === Already visible case === | ||
| Sometimes those "net" connections correspond to named visible pins inside the symbol. The Lepton manual addresses the situation as follows. | Sometimes those "net" connections correspond to named visible pins inside the symbol. The Lepton manual addresses the situation as follows. | ||
| Line 124: | Line 148: | ||
| Using a "net" special device to represent the rail device instance is consistent with use in gEDA/Lepton, since ''gnd-1.sym'' is not meant to carry a "device" attribute that would require otherwise. | Using a "net" special device to represent the rail device instance is consistent with use in gEDA/Lepton, since ''gnd-1.sym'' is not meant to carry a "device" attribute that would require otherwise. | ||
| Following our translation, the additional "GND" node connects all gnd-1.sym instances, implementing the "net" logic, as intended. The name of the second port, "rail", is made up, for now. | Following our translation, the additional "GND" node connects all gnd-1.sym instances, implementing the "net" logic, as intended. The name of the second port, "rail", is made up, for now. | ||
| - | |||
| ==== Port declarations ==== | ==== Port declarations ==== | ||