With an increasing demand for higher performance and lower power dissipation in current microprocessor, new circuit design techniques are needed for both switching logic and storage devices. In digital system, flip-flops are often thought of as memory devices, whose primary function is to store state information and data results. As complexity in microprocessor increases, both logic requirements and storage depth will also increase. This will lead to a larger number of flip-flops and hence in larger power consumption. Building a sequential machine requires memory elements which read a value, save it for some time and then write that stored value somewhere else even if the element’s input value has subsequently changed. A Boolean logic gate can compute values, but its output value will change shortly after its input changes. Every circuit used as a memory element has its own advantages and disadvantages.
A generic memory element has a memory and element associated circuitry to control access to the internal memory. Access to the internal memory is controlled by the clock input. The memory element reads its data input value when instructed by the clock and stores that value in its memory. The output reflects the stored value, probably after some delay. In CMOS circuits the memory is formed in two ways.
Keywords: flip-flops, microprocessor, CMOS
Nitin Kumar Singh Chauhan