Using Virtuoso Schematic Editor

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6.2 Deleting Components or WiresTo delete, hover over the component till it is dash-highlighted, then press the Delkey (this also works if you first click to select the component then use the DELkey or the Edit->Delete menu item, or the eraser icon at the left of the display.Caution: Once you delete an item, CDS is in the "delete'' mode, andanything you next click will also be deleted - to escape from this mode, hitthe ESC key as usual.6.3 Undoing/Re-doing an ActionYou can undo any change by typing in a u, clicking the undo icon, or using thecorresponding Edit menu item. You can actually undo a series of actions byrepeatedly typing u . The depth of this undo capability is set under Options->User Preferences in the icfb main window.If you accidentally undo something you didn't want undone, just do a "redo'' (typekey U (capital "U") or select it and use the Edit menu).6.4 Editing Component Properties (Parameters)Hover over the component to dash-highlight it, then type the q key (for "query") .Alternatively, you can select the component first by left-clicking on it, and thenuse either the q key, or click the Property icon on the toolbar, or select Edit->Properties. If you don't click to select the component first, you may end upinadvertently editing the properties of a different component - the component youhad last selected.From the Edit Properties window, you can change the values of the component'sparameters, for example, to change the voltage of a voltage supply, or to changethe width of a transistor, etc. The units for each property are defined by a letterwhich you are not allowed to change (even though it appears you can change it).For example, transistor dimensions are in metres (capital "M''), voltage sourcesare in volts (capital "V'') etc. The usual SI modifiers are accepted by typing themfollowing the numeric value you enter. For example, 3u means 3 x 10 -6 . Lettersm,u,n,p,f stand for milli, micro, nano, pico, and femto, respectively.Some properties are specified in terms of expressions involving variables orother property names. This allows, for example, a transistor width to be specifiedas a fixed multiple of its length, or instead to be specified by a variable whosevalue will be filled in later by the user during a simulation run.With CDS, the units are an integral part of the Property, so that when filling invariable values (for example, later on in a simulation), the unit must not be typed
in with the value of the variable. It is therefore incorrect to type in 3V for the valueof a voltage variable - CDS would interpret this to mean "3V" volts, which isundefined , rather than the "3" volts you intended.7. Printing a SchematicSelect Design->Plot from the main Schematic Editor menu, and set up forprinting as described under "Using the Cadence Design System". You will needto click on the Plot Options button in the dialog box that appears in order tochoose the printer type, plus other options.8. Saving a DesignYou can save a design from the Design menu, but the Cadence documentationrecommends that you always use Check and Save rather than just Save. Youcan also save the design under a different name (for later editing to make adifferent version, say), but note that the current file name stays what it was. So ifyou want to save to a new name, and edit that newly-named design, you will firsthave to open it by using Design->Open. This behaviour is different from mosteditors and programs you may be used to, so be careful you are working on theproperly named schematic.9. Creating a Symbol Cellview for Your DesignYou can "package'' your designed cell into a convenient module that has agraphical symbol (a "symbol''), which allows you to then incorporate it as a wholeinto another design schematic. For example, you could package an inverterdesign schematic named, say inv_small, containing an NMOS and a PMOStransistor into a normal inverter symbol (i.e. a triangular package with one input,and one output, with a bubble at the output).Before you can make the symbol cellview, you need to add "pins'' (from the Addmenu, or by using the pin tool on the toolbar) to define where the inputs andoutputs are. Then when you select Design->Create Cellview->FromCellview, a cellview editor opens allowing you to define the shape of thesymbol that will house your design, labels, etc.Now you could open a new design, and by picking inv_small from your library,drop in an instance that would appear as the triangular inverter symbol, havingterminals to which you will connect. By using this feature, you can build updesigns hierarchically, with simple logic cells having few transistors at the bottomof the hierarchy, and complex cells ( that contain simpler lower-level cells) at thetop of the hierarchy. You should already be familiar with this approach if youhave used the Altera Design software.
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