6.7. Connections - hierarchical labels

6.7. Connections - hierarchical labels

Each pin of the sheet symbol just created, must correspond to a label called hierarchical Label in the sub-sheet. Hierarchical labels are similar to labels, but they provide connections between sub-sheet and root sheet. The graphical representation of the two complementary labels (pin and HLabel) is similar. Hierarchical labels creation is made with the tool .

See below a root sheet example:

Notice pin VCC_PIC, connected to connector JP1.

Here are the corresponding connections in the sub-sheet :

You find again, the two corresponding hierarchical labels, providing connection between the two hierarchical sheets.

Note

You can use hierarchical labels and hierarchy pins to connect two buses, according to the syntax (Bus [N. .m]) previously described.

6.7.1. Labels, hierarchical labels, global labels and invisible power pins

Here are some comments on various ways to provide connections, other than wire connections.

Simple labels

Simple labels have a local capacity of connection, i.e. limited to the schematic sheet where they are placed. This is due to the fact that :

• Each sheet has a sheet number.
• This sheet number is associated to a label.

Thus, if you place the label “TOTO” in sheet n° 3, in fact the true label is “TOTO_3”. If you also place a label “TOTO” in sheet n° 1 (root sheet) you place in fact a label called “TOTO_1”, different from “TOTO_3”. This is always true, even if there is only one sheet.

Hierarchical labels

What is said for the simple labels is also true for hierarchical labels.

Thus in the same sheet, a HLabel “TOTO” is considered to be connected to a local label “TOTO”, but not connected to a HLabel or label called “TOTO” in another sheet.

However a HLabel is considered to be connected to the corresponding SheetLabel symbol in the hierarchical symbol placed in the root sheet.

Invisible power pins

It was seen that invisible power pins were connected together if they have the same name. Thus all the power pins declared “Invisible Power Pins” and named VCC are connected and form the equipotential VCC, whatever the sheet they are placed on.

This means that if you place a VCC label in a sub-sheet, it will not be connected to VCC pins, because this label is actually VCC_n, where n is the sheet number.

If you want this label VCC to be really connected to the equipotential VCC, it will have to be explicitly connected to an invisible power pin, thanks to a VCC power port.

6.7.2. Global labels

Global labels that have an identical name are connected across the whole hierarchy.

(power labels like vcc … are global labels)