Nonvolatile content addressable memory
First Claim
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1. A multiple-valued NVCAM comprising:
- a j row by k column memory cell array, the cells of each column being connected to m bit lines, each cell including m switching means and m ferroelectric capacitors, each of the ferroelectric capacitors in one cell having a different capacitance, j, k and m being integers, one switching means and the respective ferroelectric capacitor being connected in series between the respective bit line and a drive line, the switching means being asserted by a signal on a respective word line; and
data sensing means for comparing the data stored in the cells to reference data,the data sensing means comprising;
data acquisition means for acquiring the comparison results; and
j data comparison means, each data comparison means being connected to the cells of the respective column and the data acquire means, each data comparison means comparing the data stored in the cells of the respective column to the reference data to provide comparison results to the data acquire means.
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Abstract
Binary and multiple-valued nonvolatile content addressable memories (NVCAMs) use ferroelectric capacitors as nonvolatile storage elements. The operation of the NVCAMs is accessed either in serial or in parallel. In a 2-bit NVCAM of a parallel access structure, search operation is performed by a simultaneous access to a 4-level polarization of the ferroelectric capacitor. The total number of search operations is reduced.
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Citations
12 Claims
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1. A multiple-valued NVCAM comprising:
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a j row by k column memory cell array, the cells of each column being connected to m bit lines, each cell including m switching means and m ferroelectric capacitors, each of the ferroelectric capacitors in one cell having a different capacitance, j, k and m being integers, one switching means and the respective ferroelectric capacitor being connected in series between the respective bit line and a drive line, the switching means being asserted by a signal on a respective word line; and data sensing means for comparing the data stored in the cells to reference data, the data sensing means comprising; data acquisition means for acquiring the comparison results; and j data comparison means, each data comparison means being connected to the cells of the respective column and the data acquire means, each data comparison means comparing the data stored in the cells of the respective column to the reference data to provide comparison results to the data acquire means. - View Dependent Claims (2, 3)
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4. A multiple-valued NVCAM comprising:
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a j row by k column memory cell array, the cells of each column being connected to m bit lines, each cell including m switching means and m ferroelectric capacitors, j, k and m being integers, one switching means and the respective ferroelectric capacitor being connected in series between the respective bit line and a drive line, the switching means being asserted by a signal on a respective word line; and data sensing means for comparing the data stored in the cells to reference data, m being two, the bit lines of each column being first and second bit lines, the cell including first and second ferroelectric capacitors, and the NVCAM stores four-valued data, the capacitor area size of the first ferroelectric capacitor being different from that of the second ferroelectric capacitor. - View Dependent Claims (5, 6, 7, 8, 9, 10)
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11. A multiple-valued NVCAM comprising:
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a j row by k column memory cell array, the cells of each column being connected to a bit line, m drive lines and m word lines, each cell including m FETs and m ferroelectric capacitors, the ferroelectric capacitors of one cell being charged by different voltages of "1" data on the bit line, one FET and the respective ferroelectric capacitor being connected in series between the bit line and the respective drive line, the FET being turned on and off by a signal on the respective word line, j, k and m being integers, the capacitances of the m ferroelectric capacitors of one cell being different; and data sensing means for comparing the data stored in the cells to reference data, the data sensing means comprising; data acquisition means for acquiring the comparison results; and j data comparison means, each data comparison means being connected to the cells of the respective column and the data acquire means, each data comparison means comparing the data stored in the cells of the respective column to the reference data to provide comparison results to the data acquire means. - View Dependent Claims (12)
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Specification