Memory management to save power

A method for controlling a memory that comprises a plurality of writable memory units, each memory unit being configurable:

• in a retention state wherein the memory unit retains data until a subsequent power-off of the memory unit, and in a non-retention state wherein the memory unit does not retain data and consumes less power than in the retention state;
• wherein the method comprises the following steps:
• configuring any memory unit of the memory having undergone at least one write access since its last power-up to be in the retention state;
• and
• configuring at least one memory unit of the memory that has not undergone any write access since its last power-up to be in the non-retention state;
• and
• refusing to authorize individual configuration of the state of a writable memory unit of the memory by means of a user command requesting a configuration of the memory in a selected mode of a plurality of modes.

A system, comprising:

• a memory including a plurality of writable memory units, wherein each writable memory unit is configurable to operate:
• in a retention state where the writable memory unit will retain data until a subsequent power-off of the memory unit;
• and
• in a non-retention state where the writable memory unit does not retain data and consumes less power than in the retention state;
• and
• a controller including a write register for each writable memory unit, wherein the register stores data indicating whether the memory unit has undergone at least one write access since its last power-up;
• wherein the controller is configured to:
• configure any writable memory unit of the memory having undergone at least one write access since its last power-up to be in the retention state;
• and
• configure at least one writable memory unit of the memory that has not undergone any write access since its last power-up to be in the non-retention state;
• wherein the controller is further configured, in response to a received write request in the memory, to:
• identify ones of the writable memory units targeted by said received write request;
• write to the identified writable memory units;
• set the data in the corresponding write registers to indicate that the memory unit has undergone at least one write access since its last power-up;
• and
• determine a current operating mode of the memory and:
• configure each of the identified ones of the writable memory units in the retention state if the current operating mode is a STOP mode where writable memory units can be in different states;
• and
• if the current operating mode is not the STOP mode, then do not configure each of the identified ones of the writable memory units in the retention state.

A system, comprising:

• a memory including a plurality of writable memory units, wherein each writable memory unit is configurable to operate:
• in a retention state where the writable memory unit will retain data until a subsequent power-off of the memory unit;
• and
• in a non-retention state where the writable memory unit does not retain data and consumes less power than in the retention state;
• and
• a controller including a write register for each writable memory unit, wherein the register stores data indicating whether the memory unit has undergone at least one write access since its last power-up;
• wherein the controller is configured to:
• configure any writable memory unit of the memory having undergone at least one write access since its last power-up to be in the retention state;
• and
• configure at least one writable memory unit of the memory that has not undergone any write access since its last power-up to be in the non-retention state;
• wherein the controller is further configured, in response to a received erase request in the memory to:
• identify ones of the writable memory units to be emptied by said received erase request;
• and
• set the data in the corresponding write registers to indicate that the memory unit has not undergone at least one write access since its last power-up.

A method for controlling a memory that comprises a plurality of writable memory units, each memory unit being configurable:

• in a retention state wherein the memory unit retains data until a subsequent power-off of the memory unit, and in a non-retention state wherein the memory unit does not retain data and consumes less power than in the retention state;
• wherein the method comprises the following steps:
• configuring any memory unit of the memory having undergone at least one write access since its last power-up to be in the retention state;
• configuring at least one memory unit of the memory that has not undergone any write access since its last power-up to be in the non-retention state;
• storing data indicating whether the memory unit has undergone at least one write access since its last power-up in a write register for each writable memory unit;
• receiving a memory write request;
• identifying ones of the writable memory units targeted by said memory write request;
• writing to the identified writable memory units;
• setting the data in the corresponding write registers to indicate that the memory unit has undergone at least one write access since its last power-up;
• determining a current operating mode of the memory;
• configuring each of the identified ones of the writable memory units in the retention state if the current operating mode is a STOP mode where writable memory units can be in different states;
• and
• if the current operating mode is not the STOP mode, then not configuring each of the identified ones of the writable memory units in the retention state.

A method for controlling a memory that comprises a plurality of writable memory units, each memory unit being configurable:

• in a retention state wherein the memory unit retains data until a subsequent power-off of the memory unit, and in a non-retention state wherein the memory unit does not retain data and consumes less power than in the retention state;
• wherein the method comprises the following steps:
• configuring any memory unit of the memory having undergone at least one write access since its last power-up to be in the retention state;
• configuring at least one memory unit of the memory that has not undergone any write access since its last power-up to be in the non-retention state;
• storing data indicating whether the memory unit has undergone at least one write access since its last power-up in a write register for each writable memory unit;
• receiving a memory erase request;
• identifying ones of the writable memory units to be emptied by said memory erase request;
• and
• setting the data in the corresponding write registers to indicate that the memory unit has not undergone at least one write access since its last power-up.