## (TD) 5.6 Using Macros to Examine Tradeoffs Between Different Libraries

Your diagram is now using values for the AC logic family operating at 5V. If you want to examine the impact of changing your design to 3.3V, you need to change the library specifications of the parameters to "3ac". It can get tedious changing back and forth between different libraries when you have to change the name of each parameter. To avoid this you can create a macro which you use in place of the library specification in your parameter names. Then to change libraries you just need to change the value of the macro.

To create a macro:

 •Select the ParameterLibs > Macro Substitution List menu option to open the Edit Formula Macros dialog.•Enter %ac% into the name edit box.•Select ac from the Value drop down box. The drop down box contains all libraries that have specifications.

Edit the Parameters to make them use the macro:

Now we must edit the five min & max values of your parameters, by replacing ac with %ac%. To make it easier to check our work, first setup the parameter window to display the formulas.

 •Choose the Options > Parameter Window Preferences menu and check the Display min/max formula option.
 •Adjust the columns of the parameter window so that you can see the formulas.
 •Double click on one of the formulas to open the Parameter Properties dialog. •Replace the ac with %ac% which references the macro. •Use the Prev and Next buttons to move to the next parameter.
 •When you are done the table should look like this:

Switch in the 3 volt Library using the Edit Formula Macros dialog:

 •Select the ParameterLibs > Macro Substitution List menu option to open the Edit Formula Macros dialog.•Click on the macro %ac% in the list box. This places this macro into the Name/Value edit boxes.
 •Use the Value drop down box to change the value of the macro to 3ac. Click OK to close the dialog.

Your design should now be using the 3V AC values (the delays should be longer due to the decreased supply voltage). You have now completed the parameter library tutorial.

Note: Macros can also be used to make short or alternative names for library parameters without having to edit the library names.