System and method for specifying trigger conditions of a signal measurement system using graphical elements on a graphical user interface

1. Field of the Invention A system is disclosed for enabling a user to specify one or more trigger conditions by graphically creating a pictorial representation of the trigger conditions. The pictorial representation is presented on a display window of a graphical user interface of a logic analyzer and is accomplished using trigger-condition icons. Each icon represents a trigger condition of a signal or bus. The user specifies the trigger conditions by positioning the trigger-condition icons on the display window. The user does this by selecting, dragging, and dropping the trigger-condition icons onto the display window. The display window may include one or more name elements, each associated with a signal or a bus. The user may specify the trigger condition of a first signal or bus by selecting a trigger-condition icon and positioning it at a first position on the display window in horizontal alignment with the name element of the first signal or bus. Responsive to this action, the system displays a first trigger-condition element at the first position. The user may select the trigger-condition icon from a group of icons consisting of rising-edge icon, falling-edge icon, either-edge icon, low-level icon, high-level icon, don't care icon, bus icon, positive pulse icon, and negative pulse icon. The display window may include one or more vertically aligned constant time lines. The first position may be located on a first constant-time line, and the user may select other position on other constant-time lines. The user may specify a time-limit between the first and second constant-time lines, and or between the second and third constant-time lines. This specification may be that the time-limit is an indefinite time period, or that it is less than or greater than a user-specified time period. The system includes a trigger specifier that determines a combined trigger condition for a first state corresponding to the first constant-time line based on the first and second trigger-condition elements and one or more boolean expressions. These expressions may be predetermined, or they may be user-specified.