In the Command Interpreter Window (CIW) select Design Manager --Library Browser. A window will appear enabling you to select a library of saved circuits. The libraries you see were established by the Cadence company to facilitate your design. If you drag the mouse to EE650, and click on the left button, a tree of devices now appears. If you have established your directories as described earlier, you should see the label 650mask95. Click the left mouse button on this. Now, the headings layout, schematic, and symbol appear. Primarily you are concerned with the layout option. Click on this with the left button. Several versions of this design now pop up. Version 0.0 is the earliest, and the most recent is at the bottom of your list. Click with the middle button on the most recent version. A menu now appears: Select Edit Read Properties.... Check Out.... Check In.... Cancel Checkout... Restore Backup.... Delete.... Choose edit. (note: this may cause trouble as these files are linked to my directory. If it will not let you edit, please mail me immediately.) Two windows appear. The Layer Selection Window (LSW) and the editing window. At this point, we are only concerned with navigating the editing window. The grid markings that you see are each 1 micron ( see Figure 1). Select Window-Zoom Out By 2. The inverter layout is now much smaller. Observe that grid spacing is now 5 microns ( see Figure 2). To get back to the original screen, press f (a macro for fit edit.)
FIGURE 1 Inverter with 1 micron spacing
FIGURE 2 Inverter zoomed out to 5 microns
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Zooming in and Out
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The easiest way to zoom in on a shape is to use the mouse. To do
so, press the right button, and drag the mouse across the screen
until the desired viewing area fills the box. Then release the
button. The screen zooms in on the selection box. To return to
the normal screen, again press f.
The easiest way to zoom out is to select the magnifying glass in the
left column with a minus sign. As you move the pointer on the
shape, a small window appears to tell what function this
accomplishes. Click on this box. The invertor is now again half
its size. To return to the original screen, again press f.
Some other zooming features may be found under the category Window.
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Selecting and copying a shape
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As you progress with the layout editor, you will frequently need
to select a shape or device so that you can copy it, move it, etc.
To select a single shape, move the pointer there, and click with
the left button. The shape is now outlined in white (Figure 3).
To deselect the material, click the left button on an area that
is empty. The outline now disappears. Try to select one of the
contacts on the transistor. Instead of one of the internal shapes,
the entire shape is outlined (Figure 4). This is because the
transistor was copied as an "Instance" from an earlier design.
It's features have been tested, and should not be modified.
Therefore, the program views this a shape by itself. Similarly,
if the invertor were copied into another design, the entire device
would be treated as one shape.
FIGURE 3 Selected shape outlined in white
FIGURE 4 Entire design selected.
Suppose that you have a pattern which you would like to repeat over your wafer. Click the left button near the top of the pattern. Holding the button down, drag the mouse across the screen until the entire design fills the box. Now, it is selected. Press c on your keyboard. At the bottom of the editor layout window, you are prompted to find place a referece point. Drag the mouse to the lower left corner, and click the left button. As you move the mouse, a yellow pattern of outlines follows it. To place the copy, simply click the left button where you would like it to be. Another cell appears. If you make a mistake, simply press "u". The screen appears as it did before your last command. ********************************************************************** Adding an outside cell to your desgin ********************************************************************** Earlier, we mentioned that the Invertor design contains two "Instances" of transistors. We will now look at importing another external instance into the design. Select Create -Instance. The Instance form now appears. Click on browse. The library browser window now appears. Click on nand2. The instance window automatically registers the new information. You should see the following in the Instance Window: Library tutorial Cell nand2 View layout Hide the library browser window by clicking on the box in the upper left corner. If you move the cursor in the editing window, the outline of the nand gate will follow the pointer until you place it. Once it is placed, press esc. to cancel the instance. Press f to fit the edit. As you can see, the instance is a very powerful feature of Cadence. It allows the user to create a basic design, such as a transistor, and have the luxury of using the same design for each circuit. As mentioned before, you can not edit an instance directly. To do so, you must enter a "properties" window, and vary gate lengths, widths, and so forth. ************************************************************************** Saving your design to disk *************************************************************************** Click on Design Manager--Save As. When the options form appears, save the cell under another name. ************************************************************************ Close the current window. ************************************************************************ Select Window--Close