Obtaining data in a nonvolatile memory device through the use of descriptors

1. A data storage device comprising:

a nonvolatile memory device;

a descriptor generator configured to generate a descriptor;

a memory controller configured to generate a command to be transferred, based on the descriptor, to the nonvolatile memory device; and

a buffer including a plurality of clusters,

wherein the descriptor generator generates both a first read descriptor and a first cache output descriptor to obtain first data stored in the nonvolatile memory device, queues the first cache output descriptor when transmitting the first read descriptor to the memory controller, and determines whether to transmit the first cache output descriptor to the memory controller by referring to a state of the clusters, and

wherein the memory controller transmits a first read command to the nonvolatile memory device based on the first read descriptor, and transmits a first cache output command to the nonvolatile memory device based on the first cache output descriptor.

2. The data storage device according to claim 1 , wherein, before referring to the state of the clusters, the descriptor generator determines whether a subsequent read operation on the nonvolatile memory device is scheduled or not.

3. The data storage device according to claim 1 , wherein the descriptor generator transmits the first cache output descriptor to the memory controller when a number of free clusters included in the buffer remains unchanged for a predetermined time.

4. The data storage device according to claim 3 , wherein the descriptor generator keeps the first cache output descriptor queued when the number of free clusters does not remain unchanged for a predetermined time, and checks again the number of free clusters when a subsequent read operation on the nonvolatile memory device is not scheduled.

5. The data storage device according to claim 1 , wherein, when a subsequent read operation on second data stored in the nonvolatile memory device is scheduled before referring to the state of the clusters, the descriptor generator successively transmits a second read descriptor for the second data and the first cache output descriptor to the memory controller.

6. The data storage device according to claim 5 , wherein the memory controller successively transmits a second read command and the first cache output command to the nonvolatile memory device based on the second read descriptor and the first cache output descriptor.

7. The data storage device according to claim 6 , wherein the nonvolatile memory device performs a read operation on the second data in response to the second read command when performing a cache output operation on the first data in response to the first cache output command.

8. A method for operating a data storage device, comprising:

generating, by a descriptor generator, both a first read descriptor and a first cache output descriptor to obtain first data stored in a nonvolatile memory device;

queueing, by the descriptor generator, the first cache output descriptor when transmitting the first read descriptor to a memory controller;

transmitting a first read command to the nonvolatile memory device based on the first read descriptor, by the memory controller;

determining, by the descriptor generator, whether to transmit the first cache output descriptor to the memory controller by referring to a state of clusters included in a buffer; and

transmitting, by the memory controller, a first cache output command to the nonvolatile memory device based on the first cache output descriptor transmitted from the descriptor generator.

9. The method according to claim 8 , further comprising:

determining, before referring to the state of the clusters, whether a subsequent read operation on the nonvolatile memory device is scheduled or not, by the descriptor generator.

10. The method according to claim 8 , wherein the transmitting of the first cache output descriptor comprises:

transmitting, by the descriptor generator, the first cache output descriptor to the memory controller when a number of free clusters included in the buffer remains unchanged for a predetermined time.

11. The method according to claim 10 , wherein the transmitting of the first cache output descriptor comprises:

keeping, by the descriptor generator, the first cache output descriptor queued when the number of free clusters does not remain unchanged for a predetermined time; and

checking again, by the descriptor generator, the number of free clusters when a subsequent read operation on the nonvolatile memory device is not scheduled.

12. The method according to claim 8 , further comprising:

successively transmitting, when a subsequent read operation on second data stored in the nonvolatile memory device is scheduled before referring to the state of the clusters, a second read descriptor for the second data and the first cache output descriptor to the memory controller, by the descriptor generator.

13. The method according to claim 12 , further comprising:

successively transmitting, by the memory controller, a second read command and the first cache output command to the nonvolatile memory device based on the second read descriptor and the first cache output descriptor.

14. The method according to claim 13 , further comprising:

performing a read operation on the second data in response to the second read command when performing a cache output operation on the first data in response to the first cache output command, where the read operation and the cache output operation are performed by the nonvolatile memory device.

15. A method for operating a data storage device, comprising:

generating both a first read descriptor and a first cache output descriptor to obtain first data stored in a nonvolatile memory device;

queueing the first cache output descriptor when transmitting the first read descriptor to a memory controller;

determining whether a subsequent read operation on second data stored in the nonvolatile memory device is scheduled or not; and

determining whether to transmit the first cache output descriptor to the memory controller by referring to a state of clusters included in a buffer when a subsequent read operation is not scheduled.

16. The method according to claim 15 , further comprising:

successively transmitting a second read descriptor for the second data and the first cache output descriptor to the memory controller when a subsequent read operation is scheduled.

17. The method according to claim 15 , wherein the transmitting of the first cache output descriptor comprises:

transmitting the first cache output descriptor to the memory controller when a number of free clusters included in the buffer remains unchanged for a predetermined time.

18. The method according to claim 17 , wherein the transmitting of the first cache output descriptor comprises:

keeping the first cache output descriptor queued when the number of free clusters does not remain unchanged for a predetermined time; and

checking again the number of free clusters when a subsequent read operation on the nonvolatile memory device is not scheduled.