Parameters Panel: Set PCell Parameters

The Parameters panel appears when it is necessary to provide parameters for a parameterized cell (pcell) instantiation. These situations include

• During placement of pcell instances with the Cell Placement Control panel from the place button in the side menu.

• While editing a pc_params instance property with the Property Editor, which is obtained with the Properties button in the Edit Menu.

• If the user clicks with button 1 and the Ctrl key held on a selected pcell instance, The Parameters panel will appear. The user can reparameterize the instance.

• While editing the pc_params property of the current cell with the Cell Property Editor, which is obtained with the Cell Properties button in the Edit Menu.

• If one opens a non-native pcell for editing, the Parameters panel will appear. In this case, the label on the leftmost button is ``Open'' rather than ``Apply''. Entering parameters then pressing Open will create or find the sub-master for the parameter set, and make it the current cell. This will not happen with native pcells, which can be edited directly in Xic.

The Parameters panel provides an entry area for each pcell parameter. In cases where there more parameters than will fit within the window, a scroll bar will appear, allowing the user to scroll the parameter listing. The listing order of the parameters is as provided by the pcell.

The type of entry widget shown in the panel depends on the data type of the parameter, and the parameter constraint specification. The constraint string, if any, is obtained from the pc_params property of the pcell super-master. The following logic is used:

• If the parameter is boolean, any constraint is ignored, and a check box is created.

• If the parameter has a choice constraint, a drop-down menu containing the given choices is created. The choices can be numeric or string values.

• If the parameter has a range or step constraint, a numeric entry ``spin'' button is created. The numbers displayed in the text area follow the constraint, i.e., the range is limited, and the step value (if any) is enforced. The up/down arrows add or subtract a step value. Further, the floating-point precision used for the number will follow the resolution value of the constraint. This is described below.

• If the parameter has a numericStep constraint, the set-up is very similar to the step constraint, but an additional label will appear showing the scaleFactor, if any. This scale factor is logically appeaded to the number that appears in the entry area.

• If there is no constraint, a simple text-entry area is created.

For numeric entries, the constraint resolution value will set the number of digits that follow the decimal point in the display. For the default value of None, or if less than 1.0, the number of digits will be based on the current database resolution, as set at program startup with the DatabaseResolution variable. If the resolution is the default value of 1000, three digits will be used (1.235), otherwise four (1.2345).

Otherwise, the number of digits following the decimal will be set by the following logic:

if (resol > 1e5) num = 6
else if (resol > 1e4) num = 5
else if (resol > 1e3) num = 4
else if (resol > 1e2) num = 3
else if (resol > 1e1) num = 2
else if (resol > 1e0) num = 1
else num = 0

Note that giving a resolution of 1.0 will set the number of digits to zero, indicating integer values only (no decimal point is shown in this case).

The panel logic differs somewhat depending on the context. When editing an existing property, with the Property Editor or Cell Property Editor, the Parameters panel is ``modal'', meaning that the rest of Xic is inactive while the panel is visible. The user is expected to enter the appropriate parameter data and either press Apply which will accept the new parameter set, or Dismiss, which will abort the current parameter edit. In both cases, the Parameters panel will disappear, and Xic will return to normal status. The Reset button will revert all parameter settings in the panel to the initial settings when the panel was created, i.e., the values from the existing property string.

When placing instances, on the other hand, the Parameters panel is not modal. The parameters can be changed at any time, and the changed parameter set will apply when new instances are created, whether or not Apply is pressed. Pressing Apply will create or find the existing sub-master for the parameter set, from which the instance bounding box is obtained and used in the ghost-highlighting during instance creation. The Dismiss button will remove the panel, but the instance placement will continue. The Reset button will reset all parameter values displayed in the panel to the defaults provided in the pcell.

When opening a foreign pcell, the Parameters panel is non-model, and nothing happens unless/until Open is pressed. Pressing Open will create a new sub-master if necessary for the parameters as set, and make the sub-master the current cell for editing. Editing the sub-master is generally not a great idea, unless the user understands the issues. Changing the pc_params property, though, is a valid way to modify all instances of the master. Other changes to the sub-master will be lost, unless the sub-master is saved, possibly with the PCellKeepSubMasters variable set. Pressing Dismiss simply retires the panel. Pressing Reset returns all parameter values shown in the panel to the pcell default values.