We claim:
1. A method of activating a hydrogen storage alloy electrode, comprising the step of:
applying a plurality of current cycles to said electrode, each of said current cycles including a forward current pulse effective to at least partially charge said electrode and a reverse current pulse effective to at least partially discharge said electrode.
2. The method of claim 1, wherein the amount of charging per cycle cause by said forward current pulse is greater than the amount of discharging per cycle caused by said reverse current pulse.
3. The method of claim 1, wherein the ratio of the amount of charging per cycle to the amount of discharging per cycle is at least 5 to 1.
4. The method of claim 1, wherein the amount of charging per cycle caused by said forward current pulse is less than ten percent of total charge capacity.
5. The method of claim 1, wherein the amount of charging per cycle caused by said forward current pulse is less than one-tenth of one percent of total charge capacity.
6. A method of activating a fuel cell electrode including a hydrogen storage alloy, said method comprising the step of:
applying a plurality of current cycles to said fuel cell electrode, each of said current cycles including a forward current pulse effective to at least partially charge said anode and a reverse current pulse effective to at least partially discharge said electrode.
7. The method of claim 6, wherein the amount of charging per cycle caused by said forward current pulse is greater than the amount of discharging per cycle cause by said reverse current pulse.
8. The method of claim 6, wherein the ratio of the amount of charging per cycle to the amount of discharging per cycle is at least 5 to 1.
9. The method of claim 6, wherein the amount of charging per cycle cause by said forward current pulse is less than about ten percent of total charge capacity.
10. The method of claim 6, wherein the amount of charging per cycle caused by said forward current pulse is less than one-tenth of one percent of total charge capacity.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method comprising:
estimating respective first and second cumulative density functions for a page of memory comprising a plurality of multi-bit memory cells each having a respective value, the first and second cumulative density functions representing the values of the multi-bit memory cells in the page, and the estimating based at least in part on a decoder output of a codeword of the page;
estimating a first and a second probability density function for the page, based respectively at least in part on the first and second cumulative density functions; and
determining a center read reference voltage for reading a multi-bit memory cell in the page, based at least in part on the first and second probability density functions.
2. The method of claim 1, wherein the values of the plurality of the multi-bit memory cells are encoded according to a low density parity check (LDPC) encoding format; and
the values of the multi-bit memory cells in the page are decoded according to an LDPC decoding process to produce the decoder output.
3. The method of claim 1, further comprising:
estimating the value of each multi-bit memory cell in the page at a plurality of voltages to produce a plurality of estimated values;
adjusting at least one of the plurality of estimated values based at least in part on the decoder output to produce adjusted values; and
estimating respective first, second and third values of each of the first and second cumulative distribution functions based at least in part on the adjusted values to produce estimated first, second and third values of the first cumulative distribution function and estimated first, second and third values of the second cumulative distribution function.
4. The method of claim 3, wherein the first cumulative distribution function is based on the equation \u03a6(z)=(1+ep(z))\u22121 where \u03a6(z) represents one of the estimated first, second or third values of the first cumulative distribution function, and p(z) represents a coefficient of an equation defining the first cumulative distribution function.
5. The method of claim 4, wherein the first probability function is based at least in part on a derivative of the first cumulative distribution function.
6. The method of claim 1, further comprising:
estimating a value of each multi-bit memory cell in the page at a plurality of estimation cycles to produce a plurality of estimated values;
adjusting at least one of the plurality of estimated values based at least in part on the decoder output to produce adjusted values;
estimating respective first, second and third values of each of the first and second cumulative distribution functions based at least in part on the adjusted values.
7. The method of any of claims 1-6, wherein the values of the multi-bit memory cells in the page are a most significant bit of the multi-bit memory cells corresponding to a lower page read of the page.
8. The method of any of claims 1-6, wherein the values of the multi-bit memory cells are a least significant bit of the multi-bit memory cells corresponding to an upper page read of the page.
9. The method of claim 8, further comprising estimating the first and second cumulative distribution functions based at least in part on values related to values of a most significant bit of each of the multi-bit memory cells corresponding to a lower page read of the page.
10. The method of any of claims 1-6 wherein the center read reference voltage comprises a voltage where the first probability density function is equal to the second probability density function.
11. A computer readable media comprising instructions configured to cause an apparatus, in response to execution of the instructions by the apparatus, to:
estimate, respectively, a first and a second cumulative density function for respective values of a plurality of multi-bit non-volatile memory (NVM) cells based at least in part on one or more decoder outputs for one or more codewords for data stored in the plurality of NVM cells;
estimate a first and a second probability density function for the values of the plurality of NVM cells, based respectively at least in part on the first and second cumulative density functions; and
determine a center read reference voltage for reading an NVM cell based at least in part on the first and second probability density functions.
12. The computer readable media of claim 11, wherein the instructions cause the apparatus, in response to execution of the instructions by the apparatus, to:
estimate the value a plurality of NVM at a plurality of voltages to produce a plurality of estimated values;
adjust at least one of the plurality of estimated values based at least in part on the one or more decoder outputs to produce adjusted values;
estimate respective first, second and third values of each of the first and second cumulative distribution functions based at least in part on the adjusted values; and
estimate the first cumulative distribution function based at least in part on the estimated first, second and third values of the first cumulative distribution function, and estimate the second cumulative distribution function based at least in part on the estimated first, second and third values of the second cumulative distribution function.
13. The computer readable media of claim 11, wherein the instructions cause the apparatus, in response to execution of the instructions by the apparatus, to:
estimate the value of a plurality of NVM cells at a plurality of estimation cycles to produce a plurality of estimated values;
adjust at least one of the plurality of estimated values based at least in part on the one or more decoder outputs to produce adjusted values;
estimate respective first, second and third values of each of the first and second cumulative distribution functions based at least in part on the adjusted values.
14. The one or more computer readable media of any of claims 11-13, wherein the values of the NVM cells are a least significant bit of the NVM cells corresponding to an upper page read of the page; and
wherein the instructions cause the apparatus, in response to execution of the instructions by the apparatus, to estimate the first and second cumulative distribution functions based at least in part on a plurality of values related to a most significant bit of the NVM cells corresponding to a lower page read of the page.
15. An apparatus configured to:
estimate respective first and second cumulative density functions for a page of memory comprising a plurality of multi-bit memory cells each having a respective value, the first and second cumulative density functions representing the values of the multi-bit memory cells in the page, and the estimating based at least in part on a decoder output of a codeword of the page;
estimate a first and a second probability density function for the page, based respectively at least in part on the first and second cumulative density functions; and
determine a center read reference voltage for reading a multi-bit memory cell in the page, based at least in part on the first and second probability density functions.
16. The apparatus of claim 15, wherein the values of the plurality of the multi-bit memory cells are encoded according to a low density parity check (LDPC) encoding format; and
the values of the multi-bit memory cells in the page are decoded according to an LDPC decoding process to produce the decoder output.
17. The apparatus of claim 15 or 16, further configured to:
estimate the value of each multi-bit memory cell in the page at a plurality of voltages to produce a plurality of estimated values;
adjust at least one of the plurality of estimated values based at least in part on the decoder output to produce adjusted values; and
estimate respective first, second and third values of each of the first and second cumulative distribution functions based at least in part on the adjusted values to produce estimated first, second and third values of the first cumulative distribution function and estimated first, second and third values of the second cumulative distribution function.
18. The apparatus of claim 15 or 16, further configured to:
estimate a value of each multi-bit memory cell in the page at a plurality of estimation cycles to produce a plurality of estimated values;
adjust at least one of the plurality of estimated values based at least in part on the decoder output to produce adjusted values; and
estimate respective first, second and third values of each of the first and second cumulative distribution functions based at least in part on the adjusted values.
19. A system comprising:
a writer configured to write a value of a bit to a solid state multi-bit memory cell in a page comprising a plurality of solid state multi-bit memory cells, each solid state multi-bit memory cell in the page configured to have a value;
a reader configured to read the value of the bit from the solid state memory cell;
a decoder coupled with the reader and configured to decode a codeword of the page to produce a decoder output; and
a controller coupled with the reader and writer, and configured to:
estimate, respectively, a first and a second cumulative density function for the values of the multi-bit solid state memory cells based at least in part on the decoder output;
estimate a first and a second probability density function for the values of the multi-bit solid state memory cells, based respectively at least in part on the first and second cumulative density functions; and
determine a center read reference voltage for reading the multi-bit solid state memory cell in the page, based at least in part on the first and second probability density functions.
20. The system of claim 19, wherein the controller is further configured to:
cause the reader to read the value of each multi-bit cell in the page at a plurality of voltages to produce a plurality of estimated values;
adjust at least one of the plurality of estimated values based at least in part on the decoder output to produce adjusted values;
estimate respective first, second and third values of each of the first and second cumulative distribution functions based at least in part on the adjusted values; and
estimate the first cumulative distribution function based at least in part on the estimated first, second and third values of the first cumulative distribution function, and estimate the second cumulative distribution function based at least in part on the estimated first, second and third values of the second cumulative distribution function.
21. The system of claim 19, wherein the controller is further configured to:
cause the reader to read the value of each multi-bit cell in the page at a plurality of estimation cycles to produce a plurality of estimated values;
adjust at least one of the plurality of estimated values based at least in part on the decoder output to produce adjusted values;
estimate respective first, second and third values of each of the first and second cumulative distribution functions based at least in part on the adjusted values.
22. The system of any of claims 19-21, wherein the values of the multi-bit solid state memory cells are a most significant bit of the multi-bit solid state memory cells corresponding to a lower page read of the page.
23. The system of any of claims 19-21, wherein the values of the multi-bit solid state memory cells are a least significant bit of the multi-bit solid state memory cells corresponding to an upper page read of the page.
24. The system of claim 23, wherein the controller is further configured to estimate the first and second cumulative distribution functions based at least in part on values related to respective most significant bits of the solid state memory cells corresponding to a lower page read of the page; and
wherein the center read reference voltage is a voltage where the reader reads the values of the plurality of multi-bit solid state memory cells with a low raw bit error rate.