State retention within a data processing system
First Claim
1. A circuit comprising a state-retentive flip-flop, the flip-flop comprising:
- input and output nodes;
two latches, a master latch and a slave latch, each of the latches including a circuit element coupled in series with the input and output nodes, a first one of the latches being configured to retain a state of the flip-flop during a power managed mode in which power is decoupled from a second one of the latches;
a switch controller coupled to receive a clock signal and a power gate indicator signal, the switch controller generating a first set of switch control values dependent upon the clock signal when the power gate indicator signal has a first value and generating a second set of switch control values independent of the clock signal when the power gate indicator signal has a second value;
a first switch coupled between the input node and the master latch; and
a second switch coupled between the master latch and the slave latch, whereinthe switch controller is coupled to provide switch control signals to the first and second switches;
and wherein;
the master latch includes cross-coupled invertors and a third switch, one of the invertors and the third switch being coupled to the first switch, the third switch being coupled to receive a switch control signal from the switch controller; and
the slave latch includes cross-coupled invertors and a fourth switch, one of the invertors of the slave latch and the fourth switch being coupled to the second switch, each of the invertors of the slave latch being coupled to the output node, the fourth switch being coupled to receive a switch control signal from the switch controller, wherein an input of the slave latch located between the second switch and the one of the invertors of the slave latch is not provided as feedback to the master latch during the power managed mode.
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Accused Products
Abstract
Power consumption may be reduced through the use of power gating in which power is removed from circuit blocks or portions of circuit blocks in order to reduce leakage current. One embodiment uses a modified state retention flip-flop capable of retaining state when power is removed or partially removed from the circuit. Another embodiment uses a modified state retention buffer capable of retaining state when power is removed or partially removed from the circuit. The state retention flip-flop and buffer may be used to allow for state retention while still reducing leakage current. Also disclosed are various methods of reducing power and retaining state using, for example, the state retention flip-flops and buffers. For example, software, hardware, or a combination of software and hardware methods may be used to enter a deep sleep or idle mode while retaining state.
76 Citations
20 Claims
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1. A circuit comprising a state-retentive flip-flop, the flip-flop comprising:
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input and output nodes; two latches, a master latch and a slave latch, each of the latches including a circuit element coupled in series with the input and output nodes, a first one of the latches being configured to retain a state of the flip-flop during a power managed mode in which power is decoupled from a second one of the latches; a switch controller coupled to receive a clock signal and a power gate indicator signal, the switch controller generating a first set of switch control values dependent upon the clock signal when the power gate indicator signal has a first value and generating a second set of switch control values independent of the clock signal when the power gate indicator signal has a second value; a first switch coupled between the input node and the master latch; and a second switch coupled between the master latch and the slave latch, wherein the switch controller is coupled to provide switch control signals to the first and second switches; and wherein; the master latch includes cross-coupled invertors and a third switch, one of the invertors and the third switch being coupled to the first switch, the third switch being coupled to receive a switch control signal from the switch controller; and the slave latch includes cross-coupled invertors and a fourth switch, one of the invertors of the slave latch and the fourth switch being coupled to the second switch, each of the invertors of the slave latch being coupled to the output node, the fourth switch being coupled to receive a switch control signal from the switch controller, wherein an input of the slave latch located between the second switch and the one of the invertors of the slave latch is not provided as feedback to the master latch during the power managed mode. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A circuit comprising a state-retentive flip-flop, the flip-flop comprising:
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input and output nodes; and two latches, a master latch and a slave latch, each of the latches including a circuit element coupled in series with the input and output nodes, a first one of the latches being configured to retain a state of the flip-flop during a power managed mode in which power is decoupled from a second one of the latches; and wherein the circuit further comprises; a clock controller coupled to receive a reference clock and to provide a run clock and a sleep clock; run domain circuitry including a non-state-retentive flip-flop, the non-state-retentive flip-flop being coupled to receive the run clock signal; and sleep domain circuitry including the state-retentive flip-flop being coupled to receive the sleep clock signal. - View Dependent Claims (11)
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12. A method of reducing power loss in an information processing system having running domain circuitry and sleep domain circuitry, the method comprising:
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receiving a power gate request for diminishing power loss in the information processing system; disabling a sleep domain clock coupled to the sleep domain circuitry saving a current state of corresponding sleep domain circuitry in at least one of two series coupled latches in each flip-flop of the sleep domain circuitry; regulating a supply voltage from at least a portion of sleep domain circuitry corresponding to the power gate request, wherein the step of disabling the sleep domain clock includes confirming that the sleep clock is disabled before regulating the supply voltage of the sleep domain circuitry. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
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Specification