An unnecessary circuit operation in a clock enabler circuit accompanying toggling of a clock signal is suppressed. A state holding unit performs a holding operation of a state as to whether or not to output an output clock signal according to an internal clock signal. A clock signal output unit controls output of the output clock signal according to the state held in the state holding unit. A control unit supplies, to the state holding unit, the internal clock signal and a value of the state that are necessary for the holding operation in the state holding unit on a basis of a clock signal and a clock enable signal from an outside.

An unnecessary circuit operation in a clock enabler circuit accompanying toggling of a clock signal is suppressed. A state holding unit performs a holding operation of a state as to whether or not to output an output clock signal according to an internal clock signal. A clock signal output unit controls output of the output clock signal according to the state held in the state holding unit. A control unit supplies, to the state holding unit, the internal clock signal and a value of the state that are necessary for the holding operation in the state holding unit on a basis of a clock signal and a clock enable signal from an outside.

A test method for a delay circuit and a test circuitry are provided. The test circuitry incudes the delay circuit that essentially includes multiple serially connected logic gates, a clock pulse generator at an input end of the delay circuit for generating one or more cycles of clock signals, and a counter at an output end of the delay circuit for counting the clock signals passing through the delay circuit. The test circuitry implements a test mode by switching lines to the clock pulse generator and the counter. The test circuitry relies on a comparison result of a counting result made by the counter and a number of the cycles of the clock signals to test any failure of the delay circuit.

A digitally controlled delay line (DCDL) includes an input terminal, an output terminal, and a plurality of stages configured to propagate a signal along a first signal path from the input terminal to a selectable return stage of the plurality of stages, and along a second signal path from the return stage of the plurality of stages to the output terminal. Each stage of the plurality of stages includes a first inverter configured to selectively propagate the signal along the first signal path, a second inverter configured to selectively propagate the signal along the second signal path, and a third inverter configured to selectively propagate the signal from the first signal path to the second signal path. Each of the first and third inverters has a tunable selection configuration corresponding to greater than three output states.

A digitally controlled delay line (DCDL) includes an input terminal, an output terminal, and a plurality of stages configured to propagate a signal along a first signal path from the input terminal to a selectable return stage of the plurality of stages, and along a second signal path from the return stage of the plurality of stages to the output terminal. Each stage of the plurality of stages includes a first inverter configured to selectively propagate the signal along the first signal path, a second inverter configured to selectively propagate the signal along the second signal path, and a third inverter configured to selectively propagate the signal from the first signal path to the second signal path. Each of the first and third inverters has a tunable selection configuration corresponding to greater than three output states.

A method and apparatus for determining a set of cascading clock cycles, the method comprising inputting a set of phase changes of a set of clocks into a set of input circuits; wherein the set of phase changes are either falling phase changes or rising phase changes; wherein two phase changes of the set of clocks are fed into each input circuit of the set of input circuits, determining for each input circuit of the set of input circuits a duty cycle, storing the duty cycle for each input circuit of the input circuits in a set of duty cycles, calculating skew between the set of clocks using the duty cycles, and adjusting a delay to lower the skew between the set of clocks.

A method and apparatus for determining a set of cascading clock cycles, the method comprising inputting a set of phase changes of a set of clocks into a set of input circuits; wherein the set of phase changes are either falling phase changes or rising phase changes; wherein two phase changes of the set of clocks are fed into each input circuit of the set of input circuits, determining for each input circuit of the set of input circuits a duty cycle, storing the duty cycle for each input circuit of the input circuits in a set of duty cycles, calculating skew between the set of clocks using the duty cycles, and adjusting a delay to lower the skew between the set of clocks.

An aspect relates to an apparatus, including: a ring oscillator coupled between a first node and a first voltage rail; a control circuit coupled to the first node; a delay line coupled between a second node and the first voltage rail; and a voltage regulator including an input coupled to the first node and an output coupled to the second node.

Apparatuses and methods of DLL measurement initialization are disclosed. An example apparatus includes: a clock enable circuit that provides a first clock signal having a half frequency of an input clock signal and second clock signals having a quarter frequency of the input clock signal; a coarse delay that provides the first clock signal with a coarse delay; a fine delay that provides the first clock signal with the coarse delay and a fine delay as an output clock signal; a model delay having a feedback delay equivalent to a sum of delays of an input stage and an output stage, and provides a feedback signal that is the output clock signal with the feedback delay; and a measurement initialization circuit that performs measurement initialization. The measurement initialization circuit includes synchronizers that receive the feedback signal and the second clock signals, and provide a stop signal to the coarse delay.

Provided is an integrated circuit. The integrated circuit includes a plurality of clock generators configured to respectively generate a plurality of clock signals, a plurality of logic circuits configured to operate in synchronization with the plurality of clock signals, and controller circuitry configured to identify meta-stability information based on frequencies of the plurality of clock signals, and configured to control at least one clock generator so that at least one of the plurality of clock signals is randomly delayed in response to the meta-stability information.