Soft read for NVM that is subject to destructive reads
Techniques and mechanisms for supporting error correction of data accessed in a non-volatile (NVM) memory. In an embodiment, a memory controller performs reads each of the same codeword from the NVM, wherein a first read is based on a first reference voltage, and a second read is based on a second reference voltage. Based on the first read and the second read, confidence values are assigned each to respective bits of the codeword. Error correction comprises applying a weights to respective bits of the codeword based on the confidence values. In other embodiments, a relatively low confidence value is assigned to codeword bits that have a different value for the first read and the second read.
1 . An electronic apparatus, comprising:
one or more substrates; and
a controller coupled to the one or more substrates, the controller including circuitry to:
control access to a nonvolatile memory with a destructive read characteristic and memory cells programmed to a high resistance state that corresponds to a first threshold voltage and a low resistance state that correspond to a second threshold voltage;
perform a first read of a codeword from the nonvolatile memory at a first reference voltage of a low confidence zone, wherein the low confidence zone is between the first and second threshold voltages;
perform a second read of the codeword from the nonvolatile memory at a second reference voltage of the low confidence zone, wherein the second threshold voltage is lower than the first reference voltage;
assign a first confidence value to first bits of the codeword based on a determination that the first bits have a different value for the first read of the codeword and the second read of the codeword, wherein the first confidence value is to be lower than a second confidence value which is to be assigned to second bits of the codeword that have a same value for the first read of the codeword and the second read of the codeword; and
apply weights in an error code correction decoder based on the first confidence value and the second confidence value, wherein the circuitry is to apply a first weight to bits of the codeword that correspond to the first reference voltage, and wherein the first weight is greater than a second weight which is to be applied to bits of the codeword that correspond to the second reference voltage.
2 . The electronic apparatus of claim 1 , wherein the circuitry is further to:
correct an error in the codeword based on the first confidence value and the second confidence value.
3 . The electronic apparatus of claim 1 , wherein the circuitry is further to:
determine respective levels of the first reference voltage and the second reference voltage.
4 . The electronic apparatus of claim 3 , wherein the circuitry is further to:
assign a log-likelihood ratio (LLR) value to one or more bits of the codeword based on one of the first confidence value or the second confidence value.
5 . The electronic apparatus of claim 4 , wherein the circuitry is to:
assign a LLR value of zero to the first bits.
6 . An electronic system, comprising:
nonvolatile memory with a destructive read characteristic and memory cells programmed to a high resistance state that corresponds to a first threshold voltage and a low resistance state that correspond to a second threshold voltage; and
a controller communicatively coupled to the nonvolatile memory, the controller including circuitry to:
perform a first read of a codeword from the nonvolatile memory at a first reference voltage of a low confidence zone, wherein the low confidence zone is between the first and second threshold voltages;
perform a second read of the codeword from the nonvolatile memory at a second reference voltage of the low confidence zone, wherein the second threshold voltage is lower than the first reference voltage;
assign a first confidence value to first bits of the codeword based on a determination that the first bits have a different value for the first read of the codeword and the second read of the codeword, wherein the first confidence value is to be lower than a second confidence value which is to be assigned to second bits of the codeword that have a same value for the first read of the codeword and the second read of the codeword; and
apply weights in an error code correction decoder based on the first confidence value and the second confidence value, wherein the circuitry is to apply a first weight to bits of the codeword that correspond to the first reference voltage, and wherein the first weight is greater than a second weight which is to be applied to bits of the codeword that correspond to the second reference voltage.
7 . The electronic system of claim 6 , wherein the circuitry is further to:
correct an error in the codeword based on the first confidence value and the second confidence value.
8 . The electronic system of claim 6 , wherein the circuitry is further to:
determine respective levels of the first reference voltage and the second reference voltage.
9 . The electronic system of claim 8 , wherein the circuitry is further to:
assign a log-likelihood ratio (LLR) value to one or more bits of the codeword based on one of the first confidence value or the second confidence value.
10 . The electronic system of claim 9 , wherein the circuitry is further to:
assign a LLR value of zero to the first bits.
11 . A method, comprising:
controlling access to a nonvolatile memory with a destructive read characteristic and memory cells programmed to a high resistance state that corresponds to a first threshold voltage and a low resistance state that correspond to a second threshold voltage;
performing a first read of a codeword from the nonvolatile memory at a first reference voltage of a low confidence zone, wherein the low confidence zone is between the first and second threshold voltages;
performing a second read of the codeword from the nonvolatile memory at a second reference voltage of the low confidence zone, wherein the second threshold voltage is lower than the first reference voltage;
assigning a first confidence value to first bits of the codeword based on a determination that the first bits have a different value for the first read of the codeword and the second read of the codeword, wherein the first confidence value is lower than a second confidence value assigned to second bits of the codeword that have a same value for the first read of the codeword and the second read of the codeword; and
applying weights in an error code correction decoder based on the first confidence value and the second confidence value, comprising applying a first weight to bits of the codeword that correspond to the first reference voltage, and wherein the first weight is greater than a second weight which is to be applied to bits of the codeword that correspond to the second reference voltage.
12 . The method of claim 11 , further comprising:
correcting an error in the codeword based on the first confidence value and the second confidence value.
13 . The method of claim 11 , further comprising:
determining respective levels of the first reference voltage and the second reference voltage.
14 . The method of claim 13 , further comprising:
assigning a log-likelihood ratio (LLR) value to one or more bits of the codeword based on one of the first confidence value or the second confidence value.