Re: Understanding DFF behaviour

Posted by cadet1620 on Apr 19, 2016; 1:07am
URL: http://nand2tetris-questions-and-answers-forum.52.s1.nabble.com/Understanding-DFF-behaviour-tp4029740p4029746.html

The correct operation of an edge triggered flip-flop is to ignore the inactive clock edge.
Requiring that the input data be valid at the inactive clock edge would halve the maximum speed of circuits using that DFF.

It would possible to build a DFF that would mimic the simulator's behavior.  The simplest way would be to use two DFFs in series, one positive edge triggered and the other negative edge triggered.  Real world DFFs are available in both flavors.

why would they create a non-realistic dff?

Short answer: they were not trying for realistic; the simulator works with idealized abstract logic.

-Mark