Specification To Check Parameters

The To Check field on the Parameters tab of the Attributes pane lets you specify the names of the schematic parameters to be checked by the Check Against Source command.

For designs that have a long list of layout-only parameters that need to be ignored during a Check Against Source run, it is more efficient to specify the parameters that need to be checked instead of specifying the ones that need to be ignored. This not only reduces the effort of setting the parameters, but also makes the check and update procedures more effective as there is a lesser number of parameters to process.

You can use the To Check field to specify the list of parameters to check. When the parameters to check list is specified, Layout XL uses that list instead of using the parameters to ignore during check list.

For example, in the figure displayed below, no parameters were set for ignore. Therefore, the instance info balloon displays only those parameters that were set for check.

In Layout XL, the parameters to check can be specified using one of the following:

• LAM file
  • Cadence recommends that the parameters to check be defined in the LAM file. This ensures that the parameters to check are set at the library level and can benefit all the layout engineers using the particular cell in their design. However, any updates to the LAM file will need to be made by the CAD team engineers.
• To Check field in the Parameters tab in the CPH attributes pane
  • The To Check field displays the parameters set for checking, if defined in the LAM file. You can use the To Check field to modify the parameters to check for the current design. Any change in the CPH parameters to check list does not change the settings in the LAM file. The library-level settings remain the same, unless modified in LAM.
• Parameters to check option on the Parameters tab in the Connectivity form.
  • If the parameters to check are defined in the Connectivity form, the setting is applicable for all the Pcells. This is unlike setting the parameters to check in the LAM file, which allows the parameters to be set for a particular Pcell.
• paramsToCheck environment variable
  • By default, the environment variable is set to "", which means the parameters to check are not specified. In this case, the paramsToIgnore list is used.
    If the paramsToCheck environment variable is set, it takes precedence over the paramsToIgnoreForCheck environment variable.

When the parameters to check list is set up, the parameters in the list are the only ones that are updated by the Layout Parameters Updates or Schematic Parameter Updates commands.

Example

Let us now consider an example that illustrates a typical design scenario that uses the parameters to check list also for running the Update command.

Let us assume that you want to check the total width, w.

In this case, it is likely that you set for check only the total width (w)parameter and ignore the finger width (fw) parameter.

But:

w = fingers * fw

If you only check and update the width (w) parameter, the Pcell does not change its finger width (fw), unless the CDF callbacks are fired. Therefore, if you only want to check the width parameter (w), but want to update both the width (w) and finger width (fw) parameters, you must set the lxEvalCDFCallbacks environment variable to t.

For the current example, if CDF callback evaluation is not set, you must also include finger width (fw) as a parameter to check. This ensures that the lists of parameters to be checked and updated are in sync.

Alternatively, you can use the following options on the Parameters tab in the Connectivity form to set the parameters to check and update:

• Parameters to ignore during check
• Parameters to ignore during generation and update

Related Topic

LAM File Mapping Section

Checking a Parameter on a Cellview

Connectivity Form

paramsToCheck

paramsToIgnore

paramsToIgnoreForCheck

lxEvalCDFCallbacks