Data Sheet

Schematic Capture
29
Changing the Terminal name
If we were doing this for real, we would now have to select the VSS/VDD power supply and then
click the assign button to map our power net onto the correct supply.
If we had simply removed the label from the power terminal (instead of renaming it),
it would have been designated to the VCC net and again everything would be done
for us.
A final point worth noting is that new power supplies are created automatically when you label a
terminal with a voltage. For example, labeling a power terminal +12V would create a +12V
supply and assign the +12V net to the supply automatically. This means again that no action is
required by the user.
In general usage therefore, the software will handle the assignments of power nets to power
supplies and will create new supplies automatically. However, if you need more flexibility (for
example, an analogue ground and a digital ground) then using terminal labels and the Power
Rail Configuration dialogue gives you the control you need. Please see the reference manual
for more information if required.
Let’s change our terminal label back to VDD for consistency before we move on.
For more information please visit Power Rail Configuration in the Online Help.
Global Power Nets
Power nets and connections are always global on a given sheet on the schematic. By default,
they are also global to the design. However, if you do have a multi-sheet design and you want
separate power supplies on different sheets you can isolate the supplies by un-checking the
Global Power Nets box (Design Menu - Edit Design Properties dialogue form). This means that
you need to explicitly wire through the sheets on the design but not within a given sheet. It is
typically used only for the most complex of designs and is not relevant for the purposes of this
tutorial.