D Flip Flop Example

Slide 87 of 93

Notes:

This is a DFF example that illustrates the use of signal attributes. Notice the ‘LAST_VALUE attribute is used in the clock statement to recognize a ‘0’ to ‘1’ rising edge transition (the last value has to be a ‘0’ to avoid triggering on ‘X’ or ‘Z’ to ‘1’ transitions).

Also, the ‘STABLE attribute is used at each rising clock edge to determine if the d input has satisfied the setup time requirement.