Reading and writing waveforms from and to files can be accomplished using the "Load Trace" and "Save Trace" buttons. To apply a waveform to a signal in your design click on the "Load Trace" button. The signal selection window will be displayed with a list of signals, blocks and processes in your top-level entity. Vector signals, blocks and processes will be displayed with a "+" following their name to indicate that there is a sub-list for these items. To obtain the sub-list, click on the name with the left mouse button. For vectors, this will display the individual elements of the vector, for blocks it will display the list of signal, blocks, and process contained in that block, and for processes it will display the list of variables contained in the process. Find the signal you wish to apply the waveform to using this signal selection window and click on its name with the left mouse button. The selection window will disappear, and you will then be prompted for the filename that contains the waveform data from the input line at the bottom of the screen. The format of the waveform file is described in the Writing Configuration and Waveform Files section.

The only waveforms that you may save to a file, are the ones currently being displayed in the Trace window. To save one of these waveforms to a file, simply click on the name of the signal/variable in the Trace window with the left button of the mouse. This signal will be highlighted to indicate that it has been selected. You may now save this waveform by clicking on the "Save Trace" button. You will be prompted for the name of the file to save the waveform in on the input line at the bottom of the screen.

In order to observe the value of a signal or variable during simulation, it must be added to the Trace window or the Watch window. The difference between the Trace window and the Watch window, is the amount of information available and consequently the amount of memory used by the simulator to maintain this information. The Trace window keeps a history of all the values that a signal or variable has had, since you added it to the Trace window display. The Watch window, however, only knows about the current value of the variable or signal.

To add a signal or variable to the Trace or Watch window, click on the "Add Watch" button with the left mouse button. You will be prompted with the same signal selection window described above, accept there will be two buttons at the top of the selection window "Trace" and "Watch". Select the desired signal or variable by clicking on its name in the selection window with the left mouse button. The selected signal or variable will now be highlighted and can be added to the Trace window by clicking on the "Trace" button with the left mouse button, or to the Watch window by clicking on the "Watch" button. The selection window will remain visible so that you may select other signals or variables to add to the Trace or Watch window. When you are through adding signals and variables to the Trace and Watch windows, you may exit the selection window by selecting the "Exit Menu" item in the list (note that this item only appears in the top-level list). You will notice that in the sub-list for vector signals and variables there is entry named "hex". If you select this entry, the vector will be treated as an unsigned base two number and its value will be displayed as a hexadecimal number in the Trace window. This may only be used with signals and variables of the bit_vector type.

The "Delete Watch" button is used to remove a signal or variable from the Trace or Watch window. To remove a signal or variable select the signal or variable by clicking on its name in the Trace or Watch window. It will be highlighted to indicated that it has been selected. You may now remove it by clicking on the "Delete Watch" button.

The next two buttons control the execution of your design. When you click on the "Step" button your design will execute for a small interval of simulation time. By default, this is 1ns. You may change this value with the "Time Step" button described bellow, or with a configuration file as described in the Writing Configuration and Waveform Files section. The "Run" button is used to execute the design for long periods of time. Each time you click on the run button you will be prompted for the amount of time to simulate. This value is entered as a VHDL time literal (ex. 1us).

The "Time Step" button is used to change the simulation time used with the Step button. When you click the Time Step button with the left mouse button, you will be prompted for the new length of simulation to be applied when the Step button is used. This value is entered as a VHDL time literal (ex. 1us).

The "Re-start" button is used to reset the simulation back to time 0. When you click on this button, the executable will be reloaded and the simulator is re-initialized, and the Trace window will be cleared.

The "Setup" button is used to load a configuration file. The configuration file allows you to store a certain setup of the user interface in a file for re-use. For more information see the section below on configuration files. When you select this button, you will be prompted for the configuration filename on the input line at the bottom of the screen. The configuration file may also be specified at the DOS command line when you run SVE.

Finally, the "Quit" button is used to exit SVE.