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Directs the Fitter to place logic elements in a device in one or both of the following ways to meet any timing requirements and timing assignments you specify:
| Optimize timing | Directs the Fitter to optimize connections within a device to meet timing requirements and assignments, for example, tSU, tCO, and fMAX. In the Optimize timing list, you can select Normal compilation to direct the Fitter to perform normal optimization, or Extra effort to direct the Fitter to optimize timing more aggressively. The Fitter has only one one level of effort when optimizing timing for ACEX® 1K, APEX™ 20K, APEX™ II, ARM®-based Excalibur™, Cyclone™, FLEX 10KE, Mercury™, Stratix™, or Stratix™ GX devices. Therefore, if you specify any of these devices for compilation, the Optimize timing list is dimmed to indicate that it is not available. The Extra effort setting may require a longer compilation time than the Normal compilation setting. Specifying point-to-point assignments in a design may also increase the time necessary for timing-driven compilation. |
| Optimize I/O cell register placement for timing | Directs the Fitter to try to use registers in I/O cells (rather than registers in regular logic cells) to meet timing requirements and assignments that relate to I/O pins, for example, tSU and tCO. This option is off by default. Turning on this option may prevent the Fitter from meeting other timing requirements, such as fMAX. Also, specifying point-to-point assignments in a design may increase the time necessary for timing-driven compilation. The Fitter does not optimize I/O cell register placement for FLEX® 6000 devices. Therefore, if you specify a FLEX 6000 device for compilation, the Optimize I/O cell register placement for timing option is dimmed to indicate that it is not available. |
If you specify timing requirements and assignments and do not turn on one or both of these options, the Fitter places logic elements on the device without regard to the specified timing goals.
The Fitter does not perform timing-driven compilation on MAX® 3000 and MAX 7000 devices. Therefore, if you specify one of these devices for compilation, the options under Timing-driven compilation are dimmed to indicate that they are not available.
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