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Cadence Tutorial

Example : Schematic Capture (CMOS Inverter) Step 6 : Placing the pins

You must place I/O pins in your schematic to identify the inputs and the outputs. A pin can be an input or an output or an input-output (bi-directional) or a switch pin. We will only use an input pin and an output pin in our inverter schematic.

1. Click Add on the menu and then select Pin on the pull-down menu.

2. The Add Pins window appears.

3. Enter the name of your input pin in the Pin Names field.

The input name in this example is "Inp" (note that the pin names can be completely arbitrary). Also, note that the Direction option is set to Input indicating that the current pin is an input pin. As long as you enter pins of the same direction, you can enter pin names one after the other in the Pin Names field, only putting space between them. In this case, each time you place a pin, the next one will appear until all your pins are placed in the schematic.

4. Move the mouse cursor on the schematic window to place pin.

Now, you have your input pin with the name "Inp" floating in the schematic window. Point to a location to place the input pin. Since the input is the gate terminals of both transistors, it is more convenient to put this pin in front of the common node of these terminals.

4. Go back to the Add Pin window to pick up an output pin.

First, you have to change the pin direction to Output. To do this, click the left mouse button on the Direction field and select Output in the pop-up menu. Enter the output pin name, which is "Outp" in our example.

5. Place the output pin by clicking on a lcoation in the schematic window.

The procedure is completely analogous to the placement of input pins. Now it is better to put the output pin near the common drain node which is the output of the inverter circuit.

At this point, you are finished placing the pins. Press ESC on the keyboard to close the Add Pin window.

6. Connect the pins to the corresponding nodes using wires.

The wiring procedure is the same as described in the previous steps. Wiring the pins is summarized below :

Click on Add on the menu and then select Wire (narrow). You are now in the wiring mode again. Click on the input pin. => The other end of the wire is floating.

Click on a point on the common wire which connects the gate terminals of both transistors, PMOS and NMOS.

Click on the output pin. => The other end of the wire is floating.

Click on a point on the common wire which connects the drain terminals of both transistors, PMOS and NMOS.

Press ESC to close the wiring mode.

At the end of this step, your schematic should look like the following:

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Last Updated by Ilhan Hatirnaz on 10/31/1998