Systems and methods for generating erasure flags
View Patent ↗Various systems and methods for generating error indications are disclosed herein. In some cases, the error indication is used as an erasure pointer in a memory access system. As one particular example, a system for generating an erasure pointer is disclosed that includes accumulating a number of error values into an overall error value, and comparing the overall error value to an error threshold. When the overall error value exceeds the error threshold, an erasure pointer is generated. In one particular case, the error values are derived from a look up table using thermometer codes generated by an analog to digital converter. In other cases, the error values are derived from comparing a soft output with a reliability threshold.
1. A system for generating error indications, the system comprising:
a soft output decoder, wherein the soft output decoder is operable to receive a data stream and to produce a series of soft outputs and corresponding bit decisions based on the data stream;
a reliability threshold register, wherein the reliability threshold register is operable to store a reliability threshold output;
a comparator, wherein the comparator is operable to compare the reliability threshold output with each of the respective soft outputs, and wherein the comparator is operable to provide a non-zero value each time one of the soft outputs exceeds the reliability threshold output; and
an accumulator, wherein the accumulator sums the non-zero values.
2. The system of claim 1 , wherein the comparator is a first comparator, wherein the accumulator provides an accumulator error output, and wherein the system further comprises:
an error threshold register, wherein the error threshold register provides an error threshold output; and
a second comparator, wherein the second comparator compares the error threshold output with the accumulator error output, and wherein the second comparator indicates an error condition when the accumulator error output is greater than the error threshold output.
3. The system of claim 2 , wherein the system further comprises:
a latch, wherein the latch stores the indication of the error condition.
4. The system of claim 2 , wherein an erasure pointer is asserted when the error condition is indicated.
5. The system of claim 2 , wherein the erasure pointer is asserted when both the error condition is indicated and synchronized to a symbol that corresponds to the error condition.
6. The system of claim 3 , wherein the series of reliability indicators are associated with bits of a series of symbols, and wherein the latch is updated after each of the series of symbols is identified.
7. The system of claim 6 , wherein the system further comprises:
a sync detector, and wherein the series of symbols are identified based on an output of the sync detector.
8. The system of claim 1 , wherein the soft output decoder is a soft output viterbi algorithm detector.
9. The system of claim 1 , wherein the series of soft outputs and corresponding bit decisions is a series of log likelihood ratios and corresponding bit decisions.
10. A method for generating erasure pointers, the method comprising:
receiving a data stream at a soft output decoder, wherein the soft output decoder is operable to produce a series of soft outputs and corresponding bit decisions based on the data stream;
comparing each of the series of soft outputs with a reliability threshold; and
incrementing an error value each time one of the series of soft outputs exceeds the reliability threshold.
11. The method of claim 10 , wherein the method further comprises:
comparing the error value with an error threshold; and
generating an error indication where the error value exceeds the error threshold.
12. The method of claim 11 , wherein the method further comprises:
setting the reliability threshold; and
setting the error threshold.
13. The method of claim 11 , wherein the method further comprises:
storing the error indication.
14. The method of claim 11 , wherein the series of reliability indicators are associated with bits of a series of symbols, and wherein the error indication is stored after each of the series of symbols is identified.
15. The method of claim 10 , wherein the series of soft outputs and corresponding bit decisions is a series of log likelihood ratios and corresponding bit decisions.
16. The method of claim 10 , wherein the method further comprises:
asserting an erasure pointer based on the error indication and synchronized to a symbol that corresponds to the error condition.