International Business Machines Corporation

Kraig R White

Scott J Hadderman

David E Douse

A DRAM memory has a reduced refresh rate in a sleep mode to conserve power. Error Correction Codes (ECC) are used to correct errors that may arise due to the reduced refresh rate. ECC encoding occurs at the time of entering the sleep mode and ECC decoding for error detection and correction need only take place upon wake up when resuming active mode. In addition, the memory system reassigns a portion of the memory for storing the additional parity bits required for the error correcting code (ECC).

Check bit free error correction for sleep mode data retention

A method and apparatus for operating a DRAM while varying the supply voltage provided thereto. A memory system is designed to attach to a DRAM. The DRAM is capable of maintaining data stored therein until supply voltage is varied beyond a predetermined voltage change level without the performance of a refresh operation. The system includes a power source coupled to the DRAM for providing supply voltage thereto and a refresh signal generator coupled to the DRAM for causing the DRAM to perform refresh operations wherein the charges associated with data bits stored within the DRAM memory cells are refreshed thereby maintaining the data integrity of data stored in the DRAM. The relative rates of supply voltage change and refresh signal provision are adjusted so as to ensure that refresh signals are provided to the DRAM prior to a point in time at which the change in supply voltage provided to the DRAM exceeds the predetermined voltage change level. Accordingly, it is possible to achieve reliable operation of the DRAM while the supply voltage provided thereto is varied.

Apparatus for varying the refresh rate for a DRAM in response to

A method and apparatus for operating a DRAM while varying the supply voltage provided thereto. A memory system is designed to attach to a DRAM. The DRAM is capable of maintaining data stored therein until supply voltage is varied beyond a predetermined voltage change level without the performance of a refresh operation. The system includes a power source coupled to the DRAM for providing supply voltage thereto and a refresh signal generation device coupled to the DRAM for causing the DRAM to perform refresh operations wherein the charges associated with data bits stored within the DRAM memory cells are refreshed thereby maintaining the data integrity of data stored in the DRAM. The relative rates of supply voltage change and refresh signal provision are adjusted so as to ensure that refresh signals are provided to the DRAM prior to a point in time at which the change in supply voltage provided to the DRAM exceeds the predetermined voltage change level. Accordingly, it is possible to achieve reliable operation of the DRAM while the supply voltage provided thereto is varied.

Maintaining data integrity in DRAM while varying operating voltages

An apparatus may be used with a computer system having a PCMCIA interface. The apparatus employs a DRAM device and logic for converting the PCMCIA SRAM control signals into DRAM control signals, so as to permit the communication of data and control signals between the computer system and the DRAM device. The apparatus further provides controls for refreshing the DRAM device, and for arbitrating between the functions of refreshing the DRAM and providing for communication between the DRAM and the computer system. The apparatus further provides the power management functions required for operating a DRAM device in a PCMCIA environment.

PCMCIA SRAM card function using DRAM technology

A method for operating an apparatus including a DRAM with a computer system having a PCMCIA interface. The method includes the steps of converting the PCMCIA SRAM control signals sent by the computer system across the PCMCIA interface into DRAM control signals, so as to permit the communication of data and control signals between the computer system and the DRAM device. The method further includes refreshing the DRAM device and arbitrating between the refreshing of the DRAM and providing for communication between the DRAM and the computer system. The method further teaches providing power management functions required for operating a DRAM device in a PCMCIA environment.

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Colchester, VT, United States of America

Kraig R White