Multiport memory with matching address control
View Patent ↗A multiport SRAM has an array of cells, a first port, and a second port. During a period of different row addresses for the ports, the first port uses first word lines and first bit lines. The second port uses second word lines and second bit lines. In response to the second port switching to the same address as the first port to make a row match, the second port and the first port use the first plurality of word lines, but the first port uses the first plurality of bit lines and the second port uses the second plurality of bit lines. If the row match is removed by the first port changing row addresses, a correlation swap is performed so that the first port performs accesses using the second word lines and bit lines and the second port performs accesses using the first word lines and bit lines.
1. A method of operating a multiple port static random access memory (SRAM) having an array of bit cells arranged in rows and columns, a first port and a second port, a first row circuit coupled to the first port, a second row circuit coupled to the second port, a first column circuit coupled to the first port, a second column circuit coupled to the second port, a first plurality of word lines along the rows and a first plurality of bit lines along the columns working together to perform accesses to the array, and a second plurality of word lines along the rows and a second plurality of bit lines along the columns working together to perform accesses to the array, wherein each bit cell of the array is coupled to a word line from the first plurality of word lines and a word line from the second plurality of word lines, comprising:
during a first period of operation in which the rows being accessed by the first port are different than the rows being accessed by the second port, having a correlation in which the first port accesses the array using the first plurality of word lines and the first plurality of bit lines and the second port accesses the array using the second plurality of word lines and the second plurality of bit lines;
in response to the second port switching to a row address that is the same as the row address of the first port, accessing the array for the second port using the first plurality of word lines and the first plurality of bit lines; and
if the first port switches to a first different row address prior to the second port switching to a second different row address, performing a correlation swap so that the first port accesses the array using the second plurality of word lines and the second plurality of bit lines and the second port accesses the array using the first plurality of word lines and the first plurality of bit lines.
2. The method of claim 1 , wherein, if the second port switches to the second different row address prior to the first port switching to the first different row address, maintaining the correlation so that the first port accesses the array using the first plurality of word lines and the first plurality of bit lines and the second port accesses the array using the second plurality of word lines and the second plurality of bit lines.
3. The method of claim 2 , if the correlation swap is performed and there is a subsequent occurrence of the second port switching to a same row address as the first port, accessing the array for the first port and the second port using the second plurality of word lines and the second plurality of bit lines.
4. The method of claim 3 , further comprising, if after accessing the array for the first port and the second port using the second plurality of word lines and the second plurality of bit lines, the first port switches to a third different row address prior to the second port switching to a fourth different address, performing a correlation swap so that the first port accesses the array using the first plurality of word lines and the first plurality of bit lines and the second port performs accesses using the second plurality of word lines and the second plurality of bit lines.
5. The method of claim 3 , wherein, if after accessing the array for the first port and the second port using the second plurality of word lines and the second plurality of bit lines, the second port switches to a third different row address prior to the first port switching to a fourth different address, the correlation of the first port accessing the array using the second plurality of word lines and the second plurality of bit lines and the second port accessing the array using the first plurality of word lines and the first plurality of bit lines is maintained.
6. The method of claim 1 , wherein the first plurality of bit lines are accessed with a first read/write circuit and the second plurality of bit lines are accessed with a second read/write circuit.
7. The method of claim 6 , wherein, if the correlation swap occurs, the first plurality of bit lines are accessed with the second read write circuit and the second plurality of bit lines are accessed with the first read write circuit.
8. The method of claim 2 , wherein, if the correlation swap is performed and an occurrence of the first port switching to a same row address as the second port, accessing the array for the first port and the second port using the first plurality of word lines and the first plurality of bit lines.
9. The method of claim 1 , wherein if the second port switches to a same row address as the first port and a same column address as the first port, using first column circuit to perform the read and providing results of the read for the first port and for the second port.
10. The method of claim 1 , if the correlation swap has been performed, coupling the second row circuit to the first plurality of word lines, the second column circuit to the first plurality of bit lines, the first row circuit to the second plurality of word lines, and the first column circuit to the second plurality of bit lines.
11. A multiport static random access memory (SRAM) having a first correlation and a second correlation, comprising:
a first port having a first row address buffer for receiving a first row address, a first column address buffer for receiving a first column address, and a first input/output buffer;
a second port having a second row address buffer for receiving a second row address, a second column address buffer for receiving a second column address; and a second input/output buffer;
an array of memory cells arranged in rows and columns;
a first plurality of word lines along the rows and a first plurality of bit lines along the columns working together to perform accesses to the array, wherein each memory cell of the array of memory cells is coupled to a word line of the first plurality of word lines;
a second plurality of word lines along the rows and a second plurality of bit lines along the columns working together to perform accesses to the array, wherein each memory cell of the array of memory cells is coupled to a word line of the second plurality of word lines;
column circuitry coupled to the first and second plurality of bit lines;
a column switch coupled to outputs of the first column address buffer and the second column address buffer and coupled to the column circuitry;
a row switch coupled to an output of the first row address buffer and an output of the second row address buffer;
a first row decoder coupled to the first plurality of word lines and a first output of the row switch; and
a second row decoder coupled to the second plurality of word lines and a second output of the row switch,
wherein:
in the first correlation:
the column switch couples the output of the first column address buffer to a first input of the column circuitry and couples the output of the second column address buffer to a second input of the column circuitry,
in the second correlation:
the row switch couples the output of the first row address buffer to the second row decoder and the output of the second row address buffer to the first row decoder; and
the column switch couples the output of the first column address buffer to the second input of the column circuitry and couples the output of the second column address buffer to the first input of the column circuitry.
12. The multiport SRAM of claim 11 , in response to a row match in which the second row address becomes the same as the first row address when in the first correlation, the column circuitry decouples from the second plurality of bit lines and accesses a bit line pair of the first plurality of bit lines selected by the second column address.
13. The multiport SRAM of claim 12 , wherein the column circuitry is further characterized as having a first data line pair and a second data line pair in which, during the first correlation and the second correlation when no row match is present, the bit line pair of the first plurality of bit lines selected by the first column address is coupled to the first data line pair and a bit line pair of the second plurality of bit lines selected by the second column address is coupled to the second data line pair.
14. The multiport SRAM of claim 13 , wherein, in response to the row match in which the second row address becomes the same as the first row address in the first correlation, the column circuitry couples the bit line pair of the first plurality of bit lines selected by the second column address to the second data line pair.
15. The multi-port SRAM of claim 14 , wherein the column circuitry further comprises a write driver and a sense amplifier circuit coupling the first data line pair to first global data lines and the second data line pair to second global data lines.
16. The multiport SRAM of claim 15 , wherein the first port further comprises a first input/output circuit and the second port further comprises a second input/output circuit, the multiport SRAM further comprising a crossbar switch that couples the first global data lines to the first input/output circuit and the second global data lines to the second input/output circuit in the first correlation and the first global data lines to the second input/output circuit and the second global data lines to the first input/output circuit in the second correlation.
17. The multiport SRAM of claim 12 , in response to removing the row match by changing the first row address, the multiport SRAM switches to the second correlation.
18. The multiport SRAM of claim 12 , in response to removing the row match by changing the second row address, the multiport SRAM remains in the first correlation.
19. The multiport SRAM of claim 13 , wherein if a column match is present in addition to the row match, the bit line pair from the first plurality of the bit line pairs selected by both the first column address and the second column address is coupled to only a first data line.
20. A method of operating a multiple port static random access memory (SRAM) having an array of memory cells arranged in rows and columns, a first port and a second port, a first plurality of word lines along the rows and a first plurality of bit lines along the columns working together to perform accesses to the array, and a second plurality of word lines along the rows and a second plurality of bit lines along the columns working together to perform accesses to the array, wherein each bit cell of the array is coupled to a word line from the first plurality of word lines and a word line from the second plurality of word lines, comprising:
during a first period of operation in which the rows being accessed by the first port are different than the rows being accessed by second port, using the first plurality of word lines and the first plurality of bit lines to access the array for the first port and the second plurality of word lines and bit lines to access the array for the second port;
in response to the second port switching to a row address that is the same as the row address of the first port, accessing the array for the second port using the first plurality of word lines and the first plurality of bit lines; and
in response to the first port switching to a first different row address prior to the second port switching to a second different row address, accessing the array for the first port using the second plurality of word lines and the second plurality of bit lines and accessing the array for the second port using the first plurality of word lines and the first plurality of bit lines.