DYNAMIC MEMORY ARCHITECTURE EMPLOYING PASSIVE EXPIRATION OF DATA

• US 20090019341A1
• Filed: 07/12/2007
• Published: 01/15/2009
• Est. Priority Date: 10/29/2004
• Status: Active Grant

• Current Assignee: Globalfoundries US Incorporated (GlobalFoundries, Inc.)
• Original Assignee: Philip George Emma, Robert Kevin Montoye, William Robert Reohr
• Inventors: Montoye, Robert Kevin, Reohr, William Robert, Emma, Philip George
• Granted Patent: US 8,020,073 B2
• Time in Patent Office: Days
• US Class Current: 714/769
• CPC Class Codes: G06F 11/1064 in cache or content addressable memories
• CPC Class Codes: G06F 12/0893 Caches characterised by their organisation or structure
• CPC Class Codes: G06F 2212/1056 Simplification
• CPC Class Codes: G11C 11/406 Management or control of the refreshing or charge-regeneration cycles
• CPC Class Codes: G11C 11/4096 Input/output [I/O] data management or control circuits, e.g. reading or writing circuits, I/O drivers or bit-line switches
• CPC Class Codes: G11C 2029/0411 Online error correction
• CPC Class Codes: G11C 2207/2245 Memory devices with an internal cache buffer
• CPC Class Codes: G11C 2211/4062 Parity or ECC in refresh operations
• CPC Class Codes: G11C 7/1006 Data managing, e.g. manipulating data before writing or reading out, data bus switches or control circuits therefor
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management

Abstract

Apparatus for passively tracking expired data in a dynamic memory includes a time stamp memory configurable for storing information relating to a refresh status of one or more corresponding data entries in the dynamic memory. The apparatus further includes a timer configurable for defining a desired window of time in which a refresh operation of data in the dynamic memory is to occur in order to ensure that the data is valid. Control circuitry is coupled to the time stamp memory and to the timer. The control circuitry is operative to manage the information stored in the time stamp memory relating to the refresh status of the one or more corresponding data entries in the dynamic memory.

Claims

1. Apparatus for passively tracking expired data in a dynamic memory, the apparatus comprising:

a time stamp memory configurable for storing information relating to a refresh status of one or more corresponding data entries in the dynamic memory;

a timer configurable for defining a desired window of time in which a refresh operation of data in the dynamic memory is to occur in order to ensure that the data is valid; and

control circuitry coupled to the time stamp memory and to the timer, the control circuitry being operative to manage the information stored in the time stamp memory relating to the refresh status of the one or more corresponding data entries in the dynamic memory.

2. The apparatus of claim 1, wherein the window of time defined by the timer is substantially equal to a data retention time associated with one or more corresponding memory cells in the dynamic memory.

3. The apparatus of claim 1, wherein the dynamic memory comprises at least one dynamic random access memory cache.

4. The apparatus of claim 1, wherein the control circuitry is operative:

(i) to receive a requested address;

(ii) to determine whether the requested address corresponds to one or more data entries in the dynamic memory; and

(iii) when the requested address corresponds to one or more data entries in the dynamic memory, to set a time stamp in the time stamp memory associated with the one or more data entries.

5. The apparatus of claim 1, wherein the control circuitry comprises a counter configurable for counting to a count value corresponding to a number of data entries in the dynamic memory, the control circuitry, in response to the timer reaching a desired time value, being operative:

(i) to initialize the counter to index one of the data entries in the dynamic memory;

(ii) to read an entry in the time stamp memory indexed by the counter to determine the refresh status of a corresponding data entry in the dynamic memory;

(iii) to reset the refresh status of the entry in the time stamp memory indexed by the counter;

(iv) when a refresh of the entry has occurred within the window of time defined by the timer, to increment the count value of the counter to index a next successive entry in the time stamp memory;

(v) when a refresh of the entry has not occurred within the window of time defined by the timer, to invalidate the data in the dynamic memory corresponding to the entry indexed by the counter; and

(vi) to repeat steps (ii) through (v) until substantially all of the data entries in the dynamic memory have been read.

6. The apparatus of claim 5, wherein the desired limit is substantially equal to a data retention time of one or more memory cells in the dynamic memory.

7. A method for passively tracking expired data in a dynamic memory, the method comprising the steps of:

receiving an input data word;

generating an encoded data word based on the input data word and storing the encoded data word as a data entry in the dynamic memory;

in response to a requested address, reading a data entry from the dynamic memory corresponding to the requested address;

decoding the data entry corresponding to the requested address and detecting whether there are any errors in the data word read from the dynamic memory; and

generating an error signal when at least one error is detected in the data word read from the dynamic memory, the error signal indicating that the data word read from the dynamic memory comprises expired data.