Use the Results->Direct Plot->Main Form after simulation. Choose tran from the available results. You can pick whether it will append or replace (from IC5141 onwards, you also have a choice of new subwin or new window). There is a cyclic field called "Select" which can be changed from Net to Differential Nets.

Once you've done this, it will prompt you to select a positive and negative net, and will plot the differential waveform. Then it will prompt you again, and so on, until you hit escape or cancel the direct plot form.

Note that the Results->Direct Plot->Main Form was introduced in IC50; also, you need to be using the spectre simulator interface rather than the obsolete spectreS interface.

Regards,

Andrew.