When the software is not connected to a Saleae Logic device, it switches into simulation mode so potential users can explore the features of the software before deciding to buy the unit.
In simulation mode, the title bar will say [Disconnected] and the green button will say Start Simulation.
When you click Start Simulation, the capture will proceed, and the results will contain data that appear to transition randomly.
If any protocol analyzers were added to the session before the simulation mode was run, then clicking Start Simulation will generate valid protocol data. This is useful to demonstrate the functionality of each protocol analyzer, without having to record real protocol data using the Logic hardware. In the example below, we have added an the Async Serial Analyzer to Channel 0. Afterwards, clicking Start Simulation will generate serial data as shown.