Section 2: Specify Timing Requirements

Timing requirements allow you to specify the desired speed performance for the entire project, for specific design entities, or for individual nodes and pins. For example, you can specify project-wide timing requirements for the setup time (t_SU), hold time (t_H), clock-to-output delay (t_CO), pin-to-pin delays (t_PD), and maximum frequency (f_MAX).

In addition, you can override the default timing requirements on specific portions of the design by making individual timing assignments. You can also assign other individual timing assignments to cut timing paths, add external input or output delays, and invert clocks to further optimize your design. If you specify both individual and project-wide timing requirements, the Compiler uses the most stringent requirements.

You can specify timing requirements for the entire project with the Timing Settings command (Assignments menu), or you can specify timing requirements for individual entities, nodes, and pins with the Assignment Organizer command (Assignments menu). If you specify either project-wide or individual timing requirements, the Fitter optimizes the placement of logic in the device in order to meet your timing goals when you use timing-driven compilation.

The following procedures explain how to specify timing requirements and other timing analysis settings using menu commands and dialog boxes. However, you can also easily specify timing requirements and other timing analysis settings by following the steps in the Timing Wizard (Assignments menu).