AR# 10680: Exemplar 1999 - How do I prevent a signal from being optimized? ("don't touch"/"keep")
AR# 10680
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Exemplar 1999 - How do I prevent a signal from being optimized? ("don't touch"/"keep")
Description
General Description:
I wish to prevent Exemplar from optimizing logic in certain designs (as when I create a ring oscillator or an asynchronous delay). What syntax can I use to prevent Exemplar from optimizing this logic?
Solution
While Xilinx strongly recommends that asynchronous delays not be placed into designs, and ring oscillators are often unpredictable in FPGAs, the syntax for preventing optimization in Exemplar is as follows: