Clock gating

About: Clock gating is a research topic. Over the lifetime, 7838 publications have been published within this topic receiving 107903 citations.

Clock stopping schemes for data buffer

Abstract: A circuit is disclosed which allows an IN-Test to be performed on an integrated circuit (IC) without having to stop the external clock sources by disabling the IC's internal phase-locked loops. Information indicative of the IC's clock mode and of the desired stop mode is contained within the IC's clock control register. In one embodiment, the internal clocks may be stopped in either of three stop modes while operating in one of three clock modes. When it is desired to stop the IC's internal clocks, the clock control register provides a stop instruction signal STOP -- INSTR to a clock control circuit which, depending upon the particular stop mode and clock mode encoded in signal STOP -- INSTR by the clock control register, asserts a enabling signal to a disable clock circuit. In response to this active-high enabling signal, the disable clock circuit asserts a zero feedback signal to the internal phase-locked loops of the IC and thereby forces the voltage controlled oscillators within the phase-locked loops to hold internal clocks low. In this manner, the IC internal clocks may be stopped to allow a test vector to be scanned out of the IC during an IN-Test without stopping the external clock source.

Clock circuit, gsm phone, and methods of reducing electromagnetic interference

Abstract: A method of producing a clock signal with reduced electromagnetic interference spectral components includes providing a first clock signal; producing a second clock signal by delaying the first clock signal; and generating a jittered clock signal by switching between the first clock signal and the second clock signal at times selected responsive to a random number generator. A GSM phone comprises a clock configured to produce a first clock signal; a delay element coupled to the clock to produce a second clock signal by delaying the first clock signal; a multiplexer coupled to the clock and to the delay element to select between the clock and the delay element; a random number generator coupled to the multiplexer wherein the multiplexer generates a jittered clock signal by switching between the first clock signal and the second clock signal responsive to the random number generator; and a plurality of GSM phone components respectively coupled to the multiplexer to use the jittered clock signal as an input clock for the component.

Synchronous semiconductor memory device employing temporary data output stop scheme

Abstract: In a synchronous semiconductor memory device in which an internal clock signal from an internal timing clock signal generating circuit is branched in the form of a tree by driver circuits and applied to output buffers and data are output in synchronization with the internal clock signal, the driver circuit of the first stage is constituted by an NAND gate and an inverter. When output is to be temporarily stopped, an enabling signal is set to "L" level, so that the NAND gate is closed, output of the clock signal to each driver circuit is stopped, and thus power consumption is reduced.

Semiconductor memory device having altered clock frequency for address and/or command signals, and memory module and system having the same

Abstract: A semiconductor memory device includes a clock buffer which receives an external clock signal and generates a first internal clock signal having a frequency lower than that of the external clock signal and a second internal clock signal having a frequency which is the same as that of the external clock signal. An address buffer, command signal buffer and/or register receive respective input signals at a timing of the first internal clock signal. On the other hand, a data buffer inputs/outputs data at a timing of the second internal clock signal.

A clock distribution scheme for nonsymmetric VLSI circuits

Abstract: The authors propose a clock distribution scheme that minimizes the difference in the length of clock lines, which is the foremost factor responsible for clock skew in a VLSI circuit. The scheme uses the hierarchy created by the clock buffers to parallelize the distribution of the clock signal. At each hierarchical level, an exhaustive search of paths with intelligent pruning is used to determine the optimal layout of clock lines at that level. Unlike other related work in this area, both delay and skew are taken into account in determining the layout. >