System and method for controlling power states of a memory device via detection of a chip select signal

• US 6,618,791 B1
• Filed: 09/29/2000
• Issued: 09/09/2003
• Est. Priority Date: 09/29/2000
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Williams, Michael W., Dodd, James M.
• Primary Examiner(s): Verbrugge, Kevin
• Application Number:
  US09/677,138
• Time in Patent Office: 1,075 Days
• Field of Search: 711/105
• US Class Current: 711/105
• CPC Class Codes: G06F 1/3225 of memory devices
• CPC Class Codes: G06F 1/3275 Power saving in memory, e.g. RAM, cache
• CPC Class Codes: G11C 5/143 Detection of memory cassette insertion or removal; Continuity checks of supply or ground lines; Detection of supply variations, interruptions or levels G11C5/148 takes precedence; Switching between alternative supplies G11C5/141 takes precedence
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management
• CPC Class Codes: Y02D 30/50 in wire-line communication networks, e.g. low power modes or reduced link rate

Abstract

A memory system and a method for controlling power states of a memory device, or a portion thereof, are provided. The memory system includes memory devices, such as DRAMs, a memory controller, chip select lines, and logic for detecting chip select signals from the chip select lines. Each memory device, or a portion therein, is connected to the memory controller by a chip select line. Each chip select line allows the transmission of a chip select signal to a corresponding memory device, or a corresponding portion of the memory device, to select the corresponding memory device, or a portion thereof, to receive commands. Logic is provided to detect the chip select signal. When the logic detects a chip select signal provided to a corresponding memory device, or a portion thereof, that is in a power state lower than its idle state, the memory device, or a portion thereof, is automatically moved from the lower power state to a higher power state.

Claims

1. A memory system, comprising:

at least one memory device for storing data;

a memory controller that sends data and signals to the at least one memory device;

a chip select line that connects the memory controller and the at least one memory device, or a portion thereof, the chip select line allowing the transmission of a chip select signal to the at least one memory device, or the portion thereof, the chip select signal selecting the at least one memory device, or the portion thereof, to sample commands; and

an edge detection device implementing logic for detecting an edge of an assertion of the chip select signal, wherein when the logic detects the edge of the chip select signal provided to the at least one memory device, or the portion thereof, that is in a power state lower than its active state, the at least one memory device, or the portion thereof, is automatically moved from the lower power state to a higher power state, and all clock inputs to the at least one memory device, or the portion thereof, are disabled to conserve power when the at least one memory device, or the portion thereof, is in the lower power state.

2. The memory system of claim 1, wherein the lower power state to the higher power state is selected from the group of a power-down state to an active state, a power-down state to an idle state, an idle state to an active state, a self-refresh state to an active state, a self-refresh state to an idle state, and a self-refresh state to a power-down state.

3. The memory system of claim 1, further comprising a command communication path for transmitting commands from the memory controller to the at least one memory device, wherein when the chip select signal is provided to the at least one memory device, or the portion thereof, that is in the lower power state, a command on the command communication path is sampled while the at least one memory device, or the portion thereof, is being moved to the higher power state.

4. The memory system of claim 3, wherein the sampled commands are operation commands selected from the group consisting of a read command, a write command, a pre-charge command, and an activate command.

5. The memory system of claim 3, further comprising a latency adding device for introducing an added latency after the logic detects the chip select signal and the at least one memory device, or a portion thereof, is moved to the higher power state, the added latency providing delay time before the sampled command is ready to be operated on the at least one memory device, or a portion thereof.

6. The memory system of claim 5, wherein the memory system determines parameters necessary for carrying out the sampled command during the added latency.

7. The memory system of claim 5, wherein a second normal operation command is sampled during the added latency.

8. The memory system of claim 1, further comprising a command communication path for transmitting commands from the memory controller to the at least one memory device, the commands including high to low commands encoded for moving the at least one memory device, or a portion thereof, from a higher state to a lower state, wherein when the chip select signal and a high to low command are both provided to the at least one memory device, or a portion thereof, that is in a higher power state, the at least one memory device, or a portion thereof, moves from the higher power state to a lower power state.

9. The memory system of claim 8, wherein the high to low commands include a power-down command and a self-refresh command, the higher power state to the lower power state being selected from the group of an active state to an idle state, an active state to a power-down state, an active state to a self-refresh state, an idle state to a power-down state, an idle state to a self-refresh state, and a power-down state to a self-refresh state.

10. The memory system of claim 8, wherein the commands transmitted through the command data bus are further selected from the group of a read command, a write command, a null command, a pre-charge command, and an activate command.

11. A memory device, comprising:

a chip select pin for receiving a chip select signal that selects the memory device, or a portion thereof, to receive a command to be operated on the memory device;

command pins for receiving the command; and

an edge detection device implementing logic for detecting an edge of an assertion of the chip select signal, wherein when the chip select signal is received by the memory device, or the portion thereof, that is in a power state lower than its active state, the logic detects the edge of the chip select signal and the command received by the memory device, the memory device, or the portion thereof, being automatically moved from the lower power state to a higher power state, and all clock inputs to the at least one memory device, or the portion thereof, are disabled to conserve power when the at least one memory device, or the portion thereof, is in the lower power state.

12. The memory device of claim 11, wherein the received command is a normal operation command selected from the group of a read command, a write command, a pre-charge command, and an activate command.

13. The memory device of claim 11, wherein an added latency is introduced after the logic detects the chip select signal and the memory device, or a portion thereof, is moved to the higher power state, the added latency providing delay time before the sampled command is ready to be operated on the memory device, or a portion thereof.

14. The memory device of claim 11, wherein the received command includes high to low commands encoded for moving the at least one memory device, or a portion thereof, from a higher state to a lower state, wherein when the chip select signal and a high to low command are both provided to the at least one memory device, or a portion thereof, that is in a higher power state, the at least one memory device, or a portion thereof, moves from the higher power state to a lower power state.