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Chapter 2
Schematic Capture - Basics
Nets are typically assigned the next available small integer value. If two
nets are merged by wiring them together, there are rules used to decide
which of the two names the new net will bear, however in general the
smaller-numbered net wins. You may also manually assign a name to a net.
Within a single-page of a circuit, a net may be manually renamed to be the
same name as another on the same page. In this case, the two nets are
merged together. This is called virtual wiring and may be used to reduce the
complexity of circuits. Except for special reserved nets, virtual wiring may
not be used across pages or across levels in the hierarchy. Refer to the
Virtual Wiring section for more information.
Certain pre-defined named nets are considered global across an entire
design. That is to say, anytime a net at any level in the hierarchy or on any
page is re-named to one of these reserved nets, it joins this net. These
reserved nets are 0, GND, VCC, VDD, VEE, and VSS. Net 0 corresponds
to analog ground, and is the reference for all voltages during simulation.
GND is a digital ground (as it is common for the purposes of PCB layout
to wish to isolate these two ground nets).
These reserved nets are most often used in conjunction with hidden symbol
pins. These are pins that are not shown on a schematic, as they and their
accompanying wires would clutter the schematic to too great an extent, but
are nonetheless connected for the purposes of simulation and layout. For
example, a TTL digital AND gate would be connected to GND and VCC
via hidden pins.
Wiring Components Automatically
Complete the following steps to wire two components together
automatically:
NI Multisim User Manual
1.
Click on a pin from the first component to start the connection. Your
pointer turns into a crosshair ( ).
2.
Move the mouse. A wire appears, attached to your cursor.
3.
Click on a pin on the second component to finish the connection.
Multisim automatically places the wire, which snaps to an appropriate
configuration (unless you have disabled the “autowire on connection”
option, as described in the Setting Wiring Preferences section). The
wire is numbered as a net. After a wire is connected between two pins
the cursor returns to its normal mode and is ready for the next
command.
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