Self-gating pulsed flip-flop
A circuit includes a latch configured to update a stored state of the latch in response to an input data signal and a pulsed clock signal. The circuit includes a pulse generator configured to generate the pulsed clock signal based on an input clock signal, the input data signal, and a feedback signal indicative of a stored state of the latch. The pulse generator may be configured to generate a pulse enable signal based on the input data signal, the input clock signal, and the feedback signal. The pulsed clock signal may be based on the pulse enable signal and the input clock signal. The pulse generator may generate the pulsed clock signal to have a pulse of a first signal level in response to an indication that the stored state of the latch needs to change and generates the pulsed clock signal to have a second signal level, otherwise.
1. A circuit comprising:
a latch configured to update a stored state of the latch in response to an input data signal and a pulsed clock signal; and
a pulse generator configured to generate the pulsed clock signal based on an input clock signal, the input data signal, and a feedback signal indicative of the stored state of the latch,
wherein the pulse generator is configured to generate a pulse enable signal based on the input data signal, the input clock signal, and the feedback signal, the pulsed clock signal being based on the pulse enable signal and the input clock signal, and
wherein the pulse generator comprises:
a comparator configured to generate a reset signal based on the input data signal and the feedback signal, the pulse enable signal being based on the reset signal; and
a set-reset latch configured to generate the pulse enable signal based on a set signal and the reset signal.
2. The circuit, as recited in claim 1 , wherein the pulse generator further comprises:
a first logic circuit configured to combine the reset signal and the input clock signal to generate the set signal.
3. The circuit, as recited in claim 2 , wherein the first logic circuit generates the set signal to have a first logic level in response to the input clock signal and the reset signal having the first logic level and the first logic circuit generates the set signal to have a second logic level in response to at least one of the input clock signal and the reset signal having the second logic level.
4. The circuit, as recited in claim 2 , wherein the first logic circuit generates the set signal to have a first logic level in response to the reset signal having a second logic level and the input clock signal having the second logic level.
5. The circuit, as recited in claim 2 , wherein the pulse generator further comprises:
a second logic circuit configured to combine the pulse enable signal and the input clock signal to generate the pulsed clock signal.
6. The circuit, as recited in claim 5 , wherein the second logic circuit asserts the pulsed clock signal in response to the pulse enable signal having a first logic level and the input clock signal having the first logic level.
7. The circuit, as recited in claim 5 , wherein the pulsed clock signal is cleared by the second logic circuit in response to the reset signal being set.
8. The circuit, as recited in claim 1 , wherein the latch samples the input data signal on a rising edge of the input clock signal.
9. The circuit, as recited in claim 1 , wherein the pulse generator generates the pulsed clock signal to have a pulse of a first signal level in response to an indication that the stored state of the latch needs to change and generates the pulsed clock signal to have a second signal level otherwise.
10. A method comprising:
updating a stored state of a latch to correspond to a state of an input data signal in response to a pulse of a pulsed clock signal;
enabling the pulse in response to a clock signal having a first level and the stored state corresponding to a first logic level of a prior input data signal different from a second logic level of the input data signal, wherein the enabling comprises:
asserting a pulse enable signal in response to the clock signal having the first level and the stored state corresponding to the first logic level of the prior input data signal different from the second logic level of the input data signal;
generating a comparison signal based on a comparison of the input data signal and an indicator of the prior input data signal;
generating a set signal based on the clock signal and the comparison signal; and
providing a reset signal based on the comparison signal;
disabling the pulse in response to the clock signal having a second level; and
generating the pulsed clock signal to have a fixed signal level in response to the stored state corresponding to a prior input data signal having the same logic level as the input data signal.
11. The method, as recited in claim 10 , wherein the asserting comprises:
setting and resetting a second latch based on the set signal and the reset signal to generate the pulse enable signal.
12. The method, as recited in claim 11 , wherein propagation of the clock signal to the second latch is blocked in response to the input data signal and the prior input data signal having the same signal level.
13. A circuit comprising:
a latch configured to update a stored state of the latch to store a state of an input data signal in response to a first signal level of a pulsed clock signal; and
a pulse generator circuit configured to generate the pulsed clock signal to have a pulse of the first signal level in response to an indication that the stored state of the latch needs to change and generates the pulsed clock signal to have a second signal level otherwise,
wherein the pulse generator circuit comprises:
a comparator circuit responsive to a feedback signal from the latch and the input data signal; and
a set-reset latch coupled in series with the comparator circuit.