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Created 2019 02 03 (markdown)

Matthias Köfferlein 2019-02-03 22:29:30 +01:00
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# Implicit connection of nets with same label
Nets labelled with the same text are now implicitly connected even if there is no physical connection.
This can be useful to verify subcircuits. For example, a layout cell may use two different power nets which need to be connected on a higher hierarchy level. Without implicit connections it's not possible to verify the layout cell's functionality, because the connectivity extraction will render two power pins.
The implicit connection feature allows putting the same label on those two nets and make the nets
connected this way. It's not important which layers the nets are on. Only labels on the same hierarchy
level are considered.
Top-level layouts must not be extracted with this feature. Otherwise, opens may not be detected if both parts of
the nets are labelled with the same label. Hence, this feature is configurable.
The respective switch is the new "join_nets_by_label" argument of ```LayoutToNetlist#extract_netlist```.
By default, implicit connections are enabled. To disable implicit joining of nets, use
```
l2n = RBA::LayoutToNetlist::new
...
# extract netlists with implicit joining disabled
l2n.extract_netlist(false)
```