Data Sheet

LABCENTER ELECTRONICS LTD.
76
There are several points of note here. Firstly, the pads in the preview which are white are
deemed to be mapped onto component pins. This has happened as we have correctly specified
the default pin numbers when we edited the pins earlier on (pad name maps onto pin number
when present). If we had chosen to leave the pin number fields blank we would have to map all
of the pins in this dialogue form.
Secondly, we can see that there are three pads (7, 9 and 18) which are not mapped onto
component pins. Normally we would have the datasheet beside us to get the footprint mappings
but in this case pin 7 is an NC pin, pin 9 is the VSS pin and pin 18 is the VDD pin.
The NC pin is easily handled – simply type 7 in the field for NC Pins. Notice that the preview on
the right hand side will update to show that this pad is now considered dealt with.
We now need to add two ‘virtual’ pins for the power pins. These are pins which don’t need to be
on the schematic (their connection is made implicitly according to their name) as they will add
unnecessary clutter, but do need to be mapped onto pads in the footprint.
If you want to have all pins visible on the schematic (e.g. for auditing purposes) you
can certainly do so. You would add another three pins to the device, connect one of
them to an NC terminal (to put on the NC net) and connect the other two to power