Using storage cells to perform computation
A content addressable memory (CAM) unit does not have any in-cell comparator circuitry. The CAM unit includes a memory array, a multiple row decoder, a controller and an output unit. The memory array has storage cells arranged as data rows and complement rows. The multiple row decoder activates more than one row of the memory array at a time and the controller indicates to the multiple row decoder to activate data rows or complement rows as a function of an input pattern to be matched. The output unit indicates which columns generated a signal, the columns matching the pattern.
1. A CAM unit comprising:
a memory array of storage cells comprising complement rows and associated data rows,
wherein the complement rows and the data rows store data values and wherein at least one or more complement rows store data values complementary to data values stored in its associated data rows, and at least one or more complement rows store same data values as in its associated data rows;
a multiple row decoder to activate more than one row of said memory array at a time; and
a controller to receive an input pattern to be matched and to indicate to said multiple row decoder to activate data rows or complement rows responsive to the logical state of each bit in said input pattern;
wherein an indication of any one of a “don't care” and an “always fail” state is when a complement row and its associated data row store the same data values.
2. The unit according to claim 1 and wherein said memory storage cells are 3T DRAM cells.
3. The unit according to claim 1 and wherein said memory storage cells are one of the following type of memory cells: SRAM cells, DRAM cells, and non-destructive cells.
4. The unit according to claim 1 and wherein said memory storage cells provide a determinate result when multiple cells are read together.
5. The unit according to claim 1 and wherein said CAM unit is a ternary CAM unit.
6. The unit according to claim 1 and wherein said CAM unit is a quadrary CAM unit.