TimeQuest Timing Analyzer[Setup slack analysis]

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As you wrote "setup slack = clock arrival time -Tsu - Setup Uncertainty".

Setup uncertainty = 0.2 ns

Tsu = -0.21 ns

So, you get

setup slack = clock arrival time -(-0.21) -0.2 = clock arrival time +0.21 -0.20

The incr colum is the slack's increment. So, it lists +0.21 and - 0.20 respectively.

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Here the confusion start again,i given 0.2ns as clock setup uncertainty. But why in waveform window it showing as (-0.2ns) .Why the negative sign came in waveform window for uncertainty setup value ?