Non-volatile memory access control

• US 6,868,473 B2
• Filed: 10/30/2002
• Issued: 03/15/2005
• Est. Priority Date: 10/30/2002
• Status: Expired due to Fees

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Scientific-Atlanta Incorporated (Cisco Systems, Inc.)
• Inventors: Bacon, Kinney C., Johnson, Lee R.
• Primary Examiner(s): Sparks, Donald
• Assistant Examiner(s): Farrokh, Hashem
• Application Number:
  US10/283,714
• Publication Number:
  US 20040088511A1
• Time in Patent Office: 867 Days
• Field of Search: 711103-104, 711152-154, 711/158, 711163-164, 711/167, 365/185.01, 365/185.18, 365/185.29, 365/185.33, 365/222
• US Class Current: 711/103
• CPC Class Codes: G11C 16/349 Arrangements for evaluating degradation, retention or wearout, e.g. by counting erase cycles

Abstract

A system is described for controlling access to non-volatile memory. The system can include logic configured to determine whether to delay access to the non-volatile memory.

Claims

1. A method for controlling access to non-volatile memory, said method comprising the steps of:

receiving a request for access to non-volatile memory;

responsive to receiving the request, determining whether to delay access to the non-volatile memory; and

maintaining a counter for a block of the non-volatile memory, wherein the counter includes a threshold counter value that divides the counter into a delayed access portion and a non-delayed access portion, wherein counter values in the delayed access portion results in a defined delay in access in response to an access request, wherein counter values at the threshold counter value and in the non-delayed access portion results in no defined delay in access in response to an access request.

2. The method of claim 1, further including the step of delaying access to the non-volatile memory by a defined delay value if a current counter value is above a threshold counter value.

3. The method of claim 2, wherein the defined delay value is determined by subtracting the threshold counter value from a current counter value, dividing the difference by the difference between a total counter value and the threshold counter value, and multiplying the quotient by a lifecycle tick, wherein the lifecycle tick is determined by dividing a design life of the non-volatile memory by maximum specified access cycles.

4. The method of claim 1, further including the step of delaying access within a lifecycle tick until up to a maximum delay equal to the lifecycle tick, wherein the lifecycle tick is determined by dividing a design life of the non-volatile memory by maximum specified access cycles.

5. The method of claim 1, further including the step of incrementing the counter after each access.

6. The method of claim 1, further including the step of decrementing the counter after each lifecycle tick, wherein the lifecycle tick is determined by dividing a design life of the non-volatile memory by maximum specified access cycles.

7. The method of claim 1, further including the step of comparing data in a block of the non-volatile memory and data in a storage component, between which access is implemented.

8. The method of claim 7, further including the step of ignoring the request for access if the data in the storage component has the same value as the data in the compared block in the non-volatile memory.

9. The method of claim 1, wherein access includes at least one of reading from the non-volatile memory, erasing data in the non-volatile memory and writing to the non-volatile memory, erasing data in the non-volatile memory, and writing to the non-volatile memory.

10. The method of claim 1, further including the steps of determining not to delay access upon receiving an indication of a controlled shutdown to be implemented, and transferring data to at least a portion of the non-volatile memory to save the data.

11. A method for controlling access to non-volatile memory, said method comprising the steps of:

receiving a request for access to non-volatile memory; and

responsive to receiving the request, enabling access to the non-volatile memory in intervals of lifecycle ticks, wherein the lifecycle ticks are determined by dividing a design life of the non-volatile memory by maximum specified access cycles.

12. The method of claim 11, wherein access includes at least one of reading from the non-volatile memory, erasing data in the non-volatile memory and writing to the non-volatile memory, erasing data in the non-volatile memory, and writing to the non-volatile memory.

13. A method for controlling access to non-volatile memory, said method comprising the steps of:

receiving a request for access to a block of non-volatile memory;

maintaining a counter for a block of the non-volatile memory, wherein the counter includes a threshold counter value that divides the counter into a delayed access portion and a non-delayed access portion, wherein counter values in the delayed access portion results in a defined delay in access in response to an access request, wherein counter values at the threshold counter value and in the non-delayed access portion results in no defined delay in access in response to an access request;

responsive to receiving the request, determining whether to delay access to the non-volatile memory;

delaying access to the non-volatile memory by a defined delay value if a current counter value is above the threshold counter value, wherein the defined delay value is determined by subtracting the threshold counter value from a current counter value, dividing the difference by the difference between a total counter value and the threshold counter value, and multiplying the quotient by a lifecycle tick, wherein the lifecycle tick is determined by dividing a design life of the non-volatile memory by maximum specified access cycles;

incrementing the counter after each access;

decrementing the counter after each lifecycle tick; and

delaying access within the lifecycle tick until up to a maximum delay equal to the lifecycle tick.

14. A system for controlling access to non-volatile memory, said system comprising:

a non-volatile memory having an access block;

a counter for the access block;

access manager logic configured to receive a request for access to the access block of the non-volatile memory and, responsive to receiving the request, determine whether to delay access to the access block of the non-volatile memory; and

wherein the access manager logic further includes counter manager logic configured to track the counter for the access block, wherein the counter includes a threshold counter value that divides the counter into a delayed access portion and a non-delayed access portion, wherein counter values in the delayed access portion results in a defined delay in access in response to an access request, wherein counter values at the threshold counter value and in the non-delayed access portion results in no defined delay in access in response to an access request.

15. The system of claim 14, wherein the access manager logic is further configured to delay access to the non-volatile memory by a defined delay value if a current counter value is above a threshold counter value.

16. The system of claim 15, wherein the access manager logic further includes delay determiner logic, wherein the delay determiner logic is configured to calculate the defined delay value by subtracting the threshold counter value from a current counter value, dividing the difference by the difference between a total counter value and the threshold counter value, and multiplying the quotient by a lifecycle tick, wherein the lifecycle tick is determined by dividing a design life of the non-volatile memory by maximum specified access cycles.

17. The system of claim 14, wherein the access manager logic is further configured to delay access within a lifecycle tick until up to a maximum delay equal to the lifecycle tick, wherein the lifecycle tick is determined by dividing a design life of the non-volatile memory by maximum specified access cycles.

18. The system of claim 14, wherein the counter is incremented after each access.

19. The system of claim 14, wherein the counter is decremented after a lifecycle tick, wherein the lifecycle tick is determined by dividing a design life of the non-volatile memory by maximum specified access cycles.

20. The system of claim 14, wherein the access manager logic is further configured to compare data in a block of the non-volatile memory and data in a storage component, between which access is implemented.

21. The system of claim 20, wherein the access manager logic is further configured to ignore the request for access if the data in the storage component has the same value as the data in the compared block in the non-volatile memory.

22. The system of claim 14, wherein access includes at least one of reading from the non-volatile memory, erasing data in the non-volatile memory and writing to the non-volatile memory, erasing data in the non-volatile memory, and writing to the non-volatile memory.

23. The system of claim 14, wherein the access manager logic is further configured to determine not to delay access upon receiving an indication of a controlled shutdown to be implemented, and transferring data to at least a portion of the non-volatile memory to save the data.

24. A system for controlling access to non-volatile memory, said system comprising:

a non-volatile memory having at least one access block;

a counter for the access block; and

access manager logic configured to receive a request for access to the access block of the non-volatile memory and, responsive to receiving the request, enable access to the access block of the non-volatile memory in intervals of lifecycle ticks, wherein the lifecycle ticks are determined by dividing a design life of the non-volatile memory by maximum specified access cycles.

25. The system of claim 24, wherein access includes at least one of reading from the non-volatile memory, erasing data in the non-volatile memory and writing to the non-volatile memory, erasing data in the non-volatile memory, and writing to the non-volatile memory.

26. A system for controlling access to non-volatile memory, said system comprising:

a non-volatile memory having an access block;

a counter for the access block, wherein the counter includes a threshold counter value that divides the counter into a delayed access portion and a non-delayed access portion, wherein counter values in the delayed access portion results in a defined delay in access in response to an access request, wherein counter values at the threshold counter value and in the non-delayed access portion results in no defined delay in access in response to an access request, wherein the counter is incremented after each access, wherein the counter is decremented after each lifecycle tick, wherein the lifecycle tick is determined by dividing a design life of the non-volatile memory by maximum specified access cycles;

access manager logic including counter manager logic and delay determiner logic, wherein the counter manager logic is configured to track the counter for the access block, wherein the access manager logic is configured to receive a request for access to the access block of the non-volatile memory and, responsive to receiving the request, determine whether to delay access to the access block of the non-volatile memory, wherein the access manager logic is further configured to delay access to the access block of the non-volatile memory by a defined delay value if a current counter value is above the threshold counter value, wherein the access manager logic is further configured to delay access within a lifecycle tick until up to a maximum delay equal to the lifecycle tick, wherein the delay determiner logic is configured to calculate the defined delay value by subtracting the threshold counter value from a current counter value, dividing the difference by the difference between a total counter value and the threshold counter value, and multiplying the quotient by the lifecycle tick.

27. A system for controlling access to non-volatile memory on a computer-readable medium, said system comprising:

logic configured to receive a request for access to non-volatile memory;

logic configured to determine whether to delay access to an access block of the non-volatile memory in response to an access request; and

wherein the logic configured to determine is further configured to delay access to the access block of the non-volatile memory by a defined delay value if a current counter value is above a threshold counter value, wherein the logic configured to determine is further configured to delay access within a lifecycle tick until up to a maximum delay equal to a lifecycle tick, wherein the lifecycle tick is determined by dividing a design life of the non-volatile memory by maximum specified access cycles.