25-06-2012, 03:47 PM
Clocking Strategies in VLSI
[attachment=25455]
Why do we need clocks?
Clocks are the key to synchronous systems.
Clock signals provide reference points in time .
Clocks serve to slow down the signals that are too fast.
Clocked elements!!!
Latches & flip-flops are the basic elements of clocked systems.
Latches are level triggered whereas flip-flops are edge triggered.
Thus, a latch stores data whenever the clock is at a certain level whereas a flop stores data whenever there is a certain logic transission.
Clock skew!!!
Clock arrives at different nodes at different times.
Caused due to physical parameters of the circuit.
As the clock frequency increases, the circuit becomes less tolerant to clock variations.
Clock jitter!!!
Undesired deviation from the true periodicity of the clock signal.
Caused by electromagnetic interferences and cross talk with other signal carriers.
Alters the clock period, which may affect the setup and hold constraints of the flop/latch.
[attachment=25455]
Why do we need clocks?
Clocks are the key to synchronous systems.
Clock signals provide reference points in time .
Clocks serve to slow down the signals that are too fast.
Clocked elements!!!
Latches & flip-flops are the basic elements of clocked systems.
Latches are level triggered whereas flip-flops are edge triggered.
Thus, a latch stores data whenever the clock is at a certain level whereas a flop stores data whenever there is a certain logic transission.
Clock skew!!!
Clock arrives at different nodes at different times.
Caused due to physical parameters of the circuit.
As the clock frequency increases, the circuit becomes less tolerant to clock variations.
Clock jitter!!!
Undesired deviation from the true periodicity of the clock signal.
Caused by electromagnetic interferences and cross talk with other signal carriers.
Alters the clock period, which may affect the setup and hold constraints of the flop/latch.