What is the relation between propagation delay and clock frequency of flip-flop?
The longer the propagation delay, the slower your clock is able to run. The reason for this is that both Flip-Flops use the same clock. The first Flip-Flop drives its output at clock edge 1.
What is the relationship between clock frequency and clock period?
The clock period or cycle time, Tc, is the time between rising edges of a repetitive clock signal. Its reciprocal, fc = 1/Tc, is the clock frequency. All else being the same, increasing the clock frequency increases the work that a digital system can accomplish per unit time.
Why are flip flops designed to be slow?
To prevent serious hold time failures, designers must not permit too much clock skew. Sometimes flip-flops are intentionally designed to be particularly slow (i.e., large tccq ), to prevent hold time problems even when the clock skew is substantial.
What happens to the output of a delay flip flop?
Let us first describe a few basic concepts before we move on to the fault. In a standard delay flip-flop, a change in the output (Q) happens if the value at the input (D) is switched, and if the flip flop detects a rising clock edge. Typically, between two flip-flops, we have combinational logic.
How does clock skew affect the setup time?
In summary, clock skew effectively increases both the setup time and the hold time. It adds to the sequencing overhead, reducing the time available for useful work in the combinational logic. It also increases the required minimum delay through the combinational logic.
Is there a limit to the clock frequency?
Revisit Example 3.11 and assume that the system has 50 ps of clock skew. The critical path is unaffected, so the maximum clock frequency remains 3.33 GHz. The short path increases to 80 ps. This is still less than thold + tskew = 110 ps, so the circuit still violates its hold time constraint.