What is the big difference between a timing diagram editor and other types of timing analysis tools?
Timing diagrams can be drawn as soon as you have some clue as to what some of the parts for a design will be. A timing diagram is the first step to figuring out if your design works. This is different from other timing analysis tools because they require a complete circuit and models for the parts in the circuit. All the information that is necessary to draw a timing diagram is contained in data sheets which are easy to get and free unlike most simulation models.