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hold time specifies the required input data hold time for the flopflop after the rising edge of the clock, and it is not part of max frequency calculation.
normally hold time violation can not be fixed by slowing down the clock speed.
Max frequency is calculated taking the time interval between the Launch edge and capture edge of the clock. After the launch edge arriaves and the data is launched for the next FF to capture, the factors in picture are :
1. Clock to Q delay of the FF
2. Combinational and Net delays
3. and the Set up time of the capturing FF.
These are summed up to get the time period of the clock. Hold time is overlapped by Clk to Q delay of the FF. Moreover Hold time is for the data to stay at the input of the launching FF and does not contribute to the delay between the launching and capturing FFs.
hi
usually frequency of operation of a design is decided by the maximum data delay between any two adjacent flops of a design.
where delay=clk toQ +combi delay+setup.
But hold time is delay due to the clock delay and has nothing to do with data delay.
Hope this clears your doubt.
Hi,
Hold time violation means data arrivals at second flipflop early before capture clock late path.
So old data at second flipflop ignored,new data will be propagated.
We have to check whether data arrived early or not.In this criteria only hold time and skew will consider.
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