说明：  Timing constraints are used to generate guidelines for synthesis and place-and-route tools to meet the required timing performance for a design. In the current version of Designer, the timing-driven flow for Flash devices is different than the flow for Antifuse families. In the Flash design flow, Timer does not forward the constraints set in Timer to Layout. Usually, timing constraints set in Timer are saved in the Design Constraint System (DCS) using the SDC format. For Flash devices, the timing-driven place-and-route requires you to apply the constraints in GCF format. Therefore, any constraints set in Timer must be converted to GCF format to be recognized by the place-and-route tool, and not all constraints set in the Timer GUI can be converted to an equivalent GCF format. The following sections describe the Flash timing constraints flow and how the user should use the Timer tool to set timing constraints for these families.