Why is it not advisable to gate a signal with the clock?
Do not use an AND or OR gate (or any more complex combinatory term) to derive a clock signal from another clock signal. The reason for that rule is that race conditions among the multiple inputs of the combinatory term may cause multiple clock edges (glitches) where you expect only one clock edge.
What is the purpose of clock signal TW?
Digital circuits. Most integrated circuits (ICs) of sufficient complexity use a clock signal in order to synchronize different parts of the circuit, cycling at a rate slower than the worst-case internal propagation delays. In some cases, more than one clock cycle is required to perform a predictable action.
Why is a clock signal necessary in some circuits?
The signal acts like a metronome, which the digital circuit follows in time to coordinate its sequence of actions. Digital circuits rely on clock signals to know when and how to execute the functions that are programmed.
What is clock gating technique?
Clock gating is a popular technique used in many synchronous circuits for reducing dynamic power dissipation, by removing the clock signal when the circuit is not in use. Clock gating saves power by pruning the clock tree, at the cost of adding more logic to a circuit.
What is the purpose of clock?
The primary purpose of a clock is to display the time. Clocks may also have the facility to make a loud alert signal at a specified time, typically to waken a sleeper at a preset time; they are referred to as alarm clocks.
Why is an AND gate used in clock gating?
This technique of using an ‘AND’ gate is referred to as ‘Active high’ clock gating technique. Can you figure out why? Because a high on ‘EN’ signal allows the clock cycle to hit register bank, thus allowing new data in to be loaded to data out.
Can a gated clock be controlled by a HW signal?
In case of HW controlled clock enable signal, the control of gated clock is dynamically controlled by HW when needed. For example, a simple way to control the triggering of FFs is by using an XOR gate with inputs of XOR gate connected to input and output of a FF.
When to use logic high or logic low clock signal?
It can’t arrive anywhere in between the logic high or logic low level of clock signal, but, it needs to meet certain criteria, like if ‘EN’ goes high, it needs to go high before certain time of rising clock edge (resulting to setup-time check) and needs to remain high for the entire clock cycle ‘high’ (resulting in hold time check).
Can a negative edge trigger be used for clock gating?
However, this simplest form of clock gating technique has some problem of generating glitches in the clock provide to the FF, which are not desirable. These glitches can be removed by introducing a negative edge triggered FF (assuming downstream FFs are positive edge) or low-level sensitive latch at the output of the clock enable signal.