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Basic Timing Check

https://vlsiuniverse.blogspot.com/2013/06/setup-and-hold-basics-of-timing-analysis.html

 

                      Tck->q + Tprop + Tsetup  < Tperiod + Tskew 

                      Tck->q  + Tprop > Thold + Tskew

 

 

                Data valid window = Clock period – Setup window – Hold window
                Start of data valid window = Tlaunch + Thold
                End of data valid window = Tlaunch + Tperiod – Tsetup

 

 

    Setup slack = Tperiod –  (Tck->q + Tprop + Tsetup – Tskew)

Hold slack = Tck->q + Tprop – Thold – Tskew

Mitigating setup violation: Thus, we can meet the setup requirement, if violating, by

  1. Decreasing clk->q delay of launching flop
  2. Decreasing the propagation delay of the combinational cloud
  3. Reducing the setup time requirement of capturing flop
  4. Increasing the skew between capture and launch clocks
  5. Increasing the clock period
Mitigating hold violation: We can meet the hold requirement by:
  1. Increasing the clk->q delay of launching flop
  2. Decreasing the hold requirement of capturing flop
  3.  Decreasing clock skew between capturing clock and launching flip-flops

Minimum circuits to detect clockwise

The circle can rotate clockwise and back. Use minimum hardware to build a circuit to indicate the direction of rotating.? 

2 sensors are required to find out the direction of rotating. They are placed like at the drawing. One of them is connected to the data input of D flip-flop,and a second one – to the clock input. If the circle rotates the way clock sensor sees the light first while D input (second sensor) is zero – the output of the flip-flop equals zero, and if D input sensor “fires” first – the output of the flip-flop becomes high. sensor