Path Requirement - 2021.2 English

Vivado Design Suite User Guide: Design Analysis and Closure Techniques (UG906)

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2021.2 English

The path requirement represents the difference in time between the capture edge and the launch edge of a timing path.

For example, when considering the same path and clocks as in the previous section, the following path requirements exist:

Setup Path Requirement (S1) = 1*T(clk1) - 0*T(clk0) = 4ns
Setup Path Requirement (S2) = 2*T(clk1) - 1*T(clk0) = 2ns

The corresponding hold relationships are:

  • Corresponding to setup S1
    Hold Path Requirement (H1a) = (1-1)*T(clk1) - 0*T(clk0) = 0ns
    Hold Path Requirement (H1b) = 1*T(clk1) - (0+1)*T(clk0) = -2ns
  • Corresponding to setup S2
    Hold Path Requirement (H2a) = (2-1)*T(clk1) - 1*T(clk0) = -2ns
    Hold Path Requirement (H2b) = 2*T(clk1) - (1+1)*T(clk0) = -4ns

The timing analysis is performed only with the two most pessimistic requirements. In the example above, these are:

  • The setup requirement S2
  • The hold requirement H1a