HC210 datasheet(185/228 Pages) ALTERA

185 / 228 page

Altera Corporation

7–21

September 2008

Unsupported HardCopy II Timing Constraints for Classic Timing Analyzer

Unsupported

HardCopy II

Timing

Constraints for

Classic Timing

Analyzer

The Quartus II software supports a wide variety of complex timing

constraints. When using Classic Timing Analyzer for HardCopy II

design, however, some of these constraints are not translated to SDC

format constraints when the design is transferred to the HCDC. The

unsupported timing constraints for HardCopy II are listed below:

■

Clock enable multicycle paths

■

Inverted clocks

■

TSU, Th, TCO, and Min TCO

■

Internal TPD

■

Virtual clocks

■

Maximum clock and data skew

■

Maximum and minimum delay

If these constraints are used, you can still perform timing analysis in the

Quartus II software and produce the correct results. However, when a

HardCopy II archive for handoff is created, they will be ignored. The

translation of Quartus II timing constraints to SDC constraints simply

drops unsupported constraints; they do not feed forward to the HCDC.

Any unsupported constraints in a design are listed under the

Incompatible Assignments

section in the HardCopy II Advisor (see

Figure 7–5).

While it is possible to translate unsupported constraints to constraints

that are supported, the process is difficult and error-prone, often

requiring detailed analysis of the particular context in which the

constraint is used.

For this reason, Altera recommends that you use timing constraints in the

industry-standard SDC format with the TimeQuest timing analyzer or

use only supported timing constraints for Classic Timing Analyzer from

the start of your HardCopy II project. This approach avoids any

translation or constraint coverage issues that may occur later in a project

and the inevitable delay and risk that results.

In some cases, a HardCopy II project in the Quartus II software may

already be using the unsupported constraints, and you may choose either

to translate the existing, unsupported constraints, or replace them with a

new set of constraints that use only the recommended HardCopy II

timing assignments. In many cases, you may find it easier to rebuild the

constraints rather than translate existing constraints. This is because of

the ambiguous nature of many unsupported timing constraints, which

often require additional information outside of the Quartus II software

before the translation can be properly resolved. Verifying that the

translations produce the same timing constraint coverage and the same

timing analysis results can also be a time-consuming and error-prone

exercise.

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