Domino comparator capable for use in a memory array
View Patent ↗A memory including a NOR logic gate having an input coupled to a bitline (BL) and an input to receive the complement of the data value (DATABAR). The memory also including a NOR logic gate having an input coupled to the bitline bar (BLBAR) and an input to receive the data value (DATA). A combine stage is also included having an input coupled to an output of the NOR logic gate, an input coupled to an output of the NOR logic gate, and an output to provide a miss indicator (MISS). The miss indicator (MISS) indicates when a value on the bitline (BL) does not match the data value (DATA). The memory also comprising a plurality of bitcells coupled to the bitline (BL) and bitline bar (BLBAR), where each of the plurality of bitcells is coupled to a corresponding word line.
1. A memory, comprising:
a bitline;
a bitline bar;
a first NOR logic gate having a first input coupled to the bitline and a second input to receive a complement of a data value;
a second NOR logic gate having a first input coupled to the bitline bar and a second input to receive the data value; and
a combine stage having a first input coupled to an output of the first NOR logic gate and a second input coupled to an output of the second NOR logic gate, and an output to provide a miss indicator, wherein the miss indicator indicates when a value on the bitline does not match the data value.
2. The memory of claim 1 , further comprising a plurality of bitcells coupled to the bitline and the bitline bar, each of the plurality of bitcells coupled to a corresponding word line.
3. The memory of claim 2 , wherein memory comprises a tag portion, the tag portion comprising the plurality of bitcells.
4. The memory of claim 1 , further comprising:
a second bitline;
a second bitline bar;
a third NOR logic gate having a first input coupled to the second bitline and a second input to receive a complement of a second data value; and
a fourth NOR logic gate having a first input coupled to the second bitline bar and a second input to receive the second data value, wherein the combine stage has a third input coupled to an output of the third NOR logic gate and a fourth input coupled to an output of the fourth NOR logic gate.
5. The memory of claim 1 , wherein the combine stage performs a logical OR operation on the outputs of the first and second NOR logic gates to provide the miss indicator.
6. The memory of claim 1 , further comprising an input for receiving a clock signal, wherein during a precharge phase of a clock signal, the bitline and bitline bar are precharged to a first voltage.
7. The memory of claim 6 , wherein the first voltage corresponds to a logic level one.
8. The memory of claim 6 , wherein during an evaluation phase of the clock signal, values at the outputs of the first and second NOR logical gates propagate through the combine stage independent of the clock signal.
9. A method for providing a comparison result, comprising:
providing a first value, a second value, a complement of the first value, and a complement of the second value to a combinational logic stage of a comparator;
during a precharge phase of a clock signal, precharging the first value and the complement of the first value to a first voltage, wherein the first voltage propagates to an output of the combinational logic stage during the precharge phase; and
during an evaluation phase of the clock signal, the first and second inputs of the combinational logic stage propagate, independent of the clock signal, through the combinational logic stage and a combine stage coupled to the output of the combinational logic stage to provide a comparison result between the first value and the second value.
10. The method of claim 9 , wherein the first voltage represents a logic level one.
11. The method of claim 9 , wherein the first value corresponds to a bitline value of a memory array and the second value corresponds to an input data value.
12. The method of claim 9 , wherein the precharge phase corresponds to a low phase of the clock signal and the evaluation phase corresponds to a high phase of the clock signal.
13. The method of claim 9 , wherein the combine stage performs an OR function on the output of the combinational logic stage.
14. A method for providing a comparison result, comprising:
providing a first NOR logic gate having a first input to receive a first value, a second input to receive a complement of a second value, and an output;
providing a second NOR logic gate having a first input to receive a complement of the first value, a second input to receive the second value, and an output;
during a precharge phase of a clock signal, precharging the first value and the complement of the first value to a first voltage, wherein the first voltage propagates to the output of the first and second NOR logic gates during the precharge phase; and
during an evaluation phase of the clock signal, the first and second inputs of each of the first and second NOR logic gates propagate, independent of the clock signal, through the first and second NOR logic gates and a combine stage coupled to the output of the first and second NOR logic gates to provide a comparison result between the first value and the second value.
15. The method of claim 14 , wherein the first voltage represents a logic level one.
16. The method of claim 14 , wherein the first input of the first NOR logic gate is coupled to a bitline of a memory and the first input of the second NOR logic gate is coupled to a bitline bar of the memory.
17. The method of claim 16 , wherein the bitline and bitline bar of the memory correspond to a tag portion of the memory.
18. The method of claim 17 , wherein the memory comprises a static random access memory (SRAM) array.
19. The method of claim 14 , wherein the precharge phase corresponds to a low phase of the clock signal and the evaluation phase corresponds to a high phase of the clock signal.
20. The method of claim 14 , wherein the combine stage performs a logical OR function on the outputs of the first and second NOR logic gates to provide the comparison result.