Flip-flop having multiple clock sources and method therefore
View Patent ↗Briefly, in accordance with one embodiment of the invention, a flip-flop operates as a master-slave flip flop in a test mode and operates as a pulsed latch in normal operation. Two clock signals having non-overlapping transitions are used to provide and control the flow of input data.
1. An integrated circuit comprising:
a master-slave flip-flop that receives data and scan data, wherein the scan data is received by a master portion and clocked by a first clock signal into a slave portion, and wherein the slave portion includes,
an inverter;
a first transistor having a gate connected to an output of the inverter, a source connected to a first power conductor and a drain connected to an input of the inverter, and
a pair of stacked transistors coupled between the input of the inverter and a second power conductor where a gate of a first transistor of the pair of stacked transistors receives a second clock signal and a gate of a second transistor of the pair of stacked transistors receives an output signal from the inverter.
2. The integrated circuit of claim 1 , wherein the master-slave flip-flop is adapted to receive the first clock signal whose transitions do not overlap with transitions in the second clock signal.
3. The integrated circuit of claim 1 , further comprising a clock generation circuit, wherein the clock generation circuit is adapted to generate the first clock signal and the second clock signal, transitions in the first clock signal non-overlapping with transitions in the second clock signal.
4. The integrated circuit of claim 2 , wherein the master-slave flip-flop is adapted to receive a third clock signal, the first clock signal and the second clock signal being provided to the master-slave flip-flop when the integrated circuit is in a first operational mode, and the third clock being provided to the master-slave flip-flop when the integrated circuit is in a second operational mode.
5. An apparatus comprising:
a master-slave flip-flop having first and second inputs, the first input providing scan data to a master portion at a first clock signal when the apparatus is in a first operational mode, and a second clock signal to provide data at the second input to a slave portion when the apparatus is in a second operational mode, wherein the slave portion includes an inverter and a feedback inverter, where the feedback inverter includes
a first transistor having a gate connected to an output of the inverter, a source connected to a first power conductor and a drain connected to an input of the inverter; and
second and third transistors to couple the input of the inverter to a second power conductor, a gate of the second transistor is coupled to the second clock signal and a gate of the third transistor is connected to an output of the inverter.
6. The apparatus of claim 5 , wherein the first operational mode is a test mode.
7. The apparatus of claim 5 , comprising a logic circuit adapted to receive an enable signal, the enable signal provided when the apparatus is in the test mode.
8. The apparatus of claim 5 , further comprising a clock generation circuit adapted to provide the first dock signal and the second clock signal, the first clock signal having transitions that do not overlap with transitions in the second clock signal.
9. A method comprising:
clocking data from a buffer into a slave portion of a flip-flop;
generating a first clock signal and a second clock signal that have transitions that do not overlap with each other;
storing a scan value in a static latch in a master portion of the flip-flop upon a transition in the first clock cycle;
replacing the data stored in the slave portion with the scan value upon a subsequent transition in the second clock signal, wherein the slave portion includes an inverter; and
feeding back a signal from an output of the inverter to an input using a first transistor having a gate connected to an output of the inverter, a source connected to a first power conductor and a drain connected to an input of the inverter, and a pair of stacked transistors coupled between the input of the inverter and a second power conductor.
10. The method of claim 9 , wherein generating the first clock signal and the second clock signal includes enabling the first and second clock signals in a test mode.