Nonvolatile memory refresh
A system and method of refreshing a nonvolatile memory having memory cells. The method includes identifying one or more of the memory cells that do not satisfy a data retention test; remapping the one or more identified memory cells from original memory addresses to spare memory addresses; and refreshing the identified memory cells.
1. A method of refreshing a nonvolatile memory having memory cells, the method comprising:
identifying one or more of the memory cells that do not satisfy a data retention test;
remapping the one or more identified memory cells from original memory addresses to spare memory addresses;
refreshing the one or more identified memory cells; and
remapping the one or more identified memory cells from the spare addresses back to the original addresses after the nonvolatile memory ceases to be at a temperature that is greater than a predetermined temperature.
2. The method of claim 1 , wherein the spare addresses are located in a mapping table stored in a volatile memory.
3. The method of claim 1 , wherein the spare addresses are located in a mapping table stored in a nonvolatile memory.
4. The method of claim 1 , wherein the identifying and remapping steps are performed at startup.
5. The method of claim 1 , further comprising:
identifying, using an error-correcting code algorithm, one or more of the memory cells having an error; and
remapping the one or more memory cells identified as having an error from original addresses to spare memory addresses.
6. The method of claim 5 , wherein the refreshing step comprises:
reading data from the one or more identified memory cells;
correcting the read data the error-correcting algorithm; and
writing the corrected data to the one or more identified memory cells.
7. The method of claim 1 , wherein the identifying and remapping steps are performed repeatedly.
8. The method of claim 1 , wherein the identifying step comprises determining the one or more memory cells that have a write time that is less than a predetermined amount of time.
9. The method of claim 1 , wherein the identifying step comprises determining the one or more memory cells that have a read current that is less than a predetermined current value.
10. The method of claim 1 , wherein the identifying step comprises determining the one or more memory cells that have a write current that is less than a predetermined current value.
11. The method of claim 1 , wherein the identifying step comprises determining the one or more memory cells that have a resistance that is greater than a predetermined resistance value.
12. The method of claim 1 , wherein the identifying step comprises determining the one or more memory cells that have an energy barrier that is less than a predetermined energy value.
13. The method of claim 1 , wherein the nonvolatile memory is a spin-transfer torque magnetic random access memory.
14. The method of claim 1 , further comprising:
refreshing the one or more identified memory cells only.
15. The method of claim 1 , further comprising:
refreshing the one or more identified memory cells more frequently than non-identified memory cells.
16. A memory refresh system, comprising:
a nonvolatile memory having memory cells;
a memory having a mapping table; and
a controller configured to:
identify one or more of the memory cells that do not satisfy a data retention test;
remap the one or more identified memory cells from original memory addresses to spare memory addresses;
refresh the identified memory cells; and
remap the one or more identified memory cells from the spare addresses back to the original addresses after the nonvolatile memory ceases to be at a temperature that is greater than a predetermined temperature.
17. The memory refresh system of claim 16 , wherein the nonvolatile memory is a spin-transfer torque magnetic random access memory.
18. A computer program product embodied on a non-transitory computer-readable medium comprising program instructions configured such that when executed by processing circuitry cause the processing circuitry to implement a method of refreshing a nonvolatile memory having memory cells, the method comprising:
identifying one or more of the memory cells that do not satisfy a data retention test;
remapping the one or more identified memory cells from original memory addresses to spare memory addresses;
refreshing the one or more identified memory cells; and
remapping the one or more identified memory cells from the spare addresses back to the original addresses after the nonvolatile memory ceases to be at a temperature that is greater than a predetermined temperature.