CONTROLLER, SEMICONDUCTOR STORAGE DEVICE AND METHOD OF CONTROLLING DATA WRITING

• US 20140244903A1
• Filed: 06/05/2013
• Published: 08/28/2014
• Est. Priority Date: 02/28/2013
• Status: Active Grant

• Current Assignee: Kioxia Corporation
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: YANO, Hirokuni, TADOKORO, Mitsunori
• Granted Patent: US 8,990,458 B2
• Time in Patent Office: Days
• US Class Current: 711/103
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/7202 Allocation control and policies
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling
• CPC Class Codes: G11C 11/5621 using charge storage in a floating gate
• CPC Class Codes: G11C 11/5628 Programming or writing circuits; Data input circuits
• CPC Class Codes: G11C 16/0483 comprising cells having several storage transistors connected in series
• CPC Class Codes: G11C 2211/5641 Multilevel memory having cells with different number of storage levels

Abstract

According to one embodiment, a memory controller includes a mode selection part that selects one of a MLC-mode and a SLC-mode, after a write command is decoded by a command decode part, and a write part that executes a data writing to a storage memory by using one of the MLC-mode and the SLC-mode selected by the mode selection part. The mode selection part is configured to check whether a first data wrote from a host to a buffer memory is a time-continuous data that is wrote continuously during a predetermined period, execute the data writing of a second data from the buffer memory to the storage memory in the MLC-mode, when the first data is the time-continuous data, and execute the data writing of the second data from the buffer memory to the storage memory in the SLC-mode, when the first data is not the time-continuous data.

Claims

1. A memory controller configured to control a storage memory, the memory controller comprising:

a command decode part;

a mode selection part that selects one of a MLC-mode and a SLC-mode, after a write command is decoded by the command decode part; and

a write part that executes a data writing to the storage memory by using one of the MLC-mode and the SLC-mode selected by the mode selection part,

wherein the mode selection part is configured to;

check whether a first data wrote from a host to a buffer memory is a time-continuous data that is wrote continuously during a predetermined period;

execute the data writing of a second data from the buffer memory to the storage memory in the MLC-mode, when the first data is the time-continuous data; and

execute the data writing of the second data from the buffer memory to the storage memory in the SLC-mode, when the first data is not the time-continuous data.

2. The controller of claim 1,

wherein the mode selection part is configured to:

determine that the first data is the time-continuous data, when a number of free blocks as a free space in the storage memory is smaller than a first threshold value.

3. The controller of claim 2, further comprising:

a compaction part that executes a compaction of a third data wrote in the storage memory, and

an interval check part that checks an interval of write commands from the host,

wherein the compaction part is configured to;

continue the compaction until the number of the free blocks in the storage memory is equal to or larger than a second threshold value, when the interval is smaller than a predetermined value.

4. The controller of claim 3,

wherein the first threshold value is equal to or smaller than the second threshold value.

5. The controller of claim 3,

wherein the compaction part is configured to:

continue the compaction until the number of the free blocks in the storage memory is equal to or larger than a third threshold value larger than the second threshold value, when the interval of the write commands from the host is equal to or larger than the predetermined value.

6. The controller of claim 5,

wherein the compaction part is configured to:

reduce at least one of the second and third threshold value, when an average of write/erase times of all blocks in the storage memory is equal to or larger than a predetermined value.

7. The controller of claim 5,

wherein the compaction part is configured to:

inhibit the compaction, when an average of write/erase times of all blocks in the storage memory is equal to or larger than a predetermined value.

8. The controller of claim 1,

wherein the mode selection part is configured to:

determine that the first data is the time-continuous data, when an interval of write commands from the host is smaller than a predetermined value.

9. The controller of claim 1,

wherein the mode selection part is configured to:

always select the MLC-mode, when an average of write/erase times of all blocks in the storage memory is equal to or larger than a predetermined value.

10. The controller of claim 1,

further comprising a block management part that is configured to:

categorize each of all blocks in the storage memory as one of three statements of a SLC-active block, a MLC-active block and a free block, and

manage the three statements by a block management table.

11. The controller of claim 1,

further comprising a block management part that is configured to:

manage a number of write/erase times of each of all blocks in the storage memory by a block management table.

12. A semiconductor storage device comprising:

the memory controller of claim 1;

the buffer memory that temporary stores the first data from the host; and

the storage memory that stores the second data from the buffer memory,

wherein the controller controls the buffer memory and the storage memory.

13. The device of claim 12,

wherein the buffer memory is a RAM with a write speed faster than that of the storage memory.

14. The device of claim 12,

wherein the storage memory is a NAND flash memory.

15. A method of controlling a data writing using the controller of claim 1, the method comprising:

checking whether a first data wrote from a host to a buffer memory is a time-continuous data that is wrote continuously during a predetermined period;

executing the data writing of a second data from the buffer memory to the storage memory in the MLC-mode, when the first data is the time-continuous data; and

executing the data writing of the second data from the buffer memory to the storage memory in the SLC-mode, when the first data is not the time-continuous data.

16. The method of claim 15, further comprising:

determining that the first data is the time-continuous data, when a number of free blocks as a free space in the storage memory is smaller than a first threshold value.

17. The method of claim 16, further comprising:

continuing the compaction until the number of the free blocks in the storage memory is equal to or larger than a second threshold value, when an interval of write commands from the host is smaller than a predetermined value.

18. The method of claim 17,

wherein the first threshold value is equal to or smaller than the second threshold value.

19. The method of claim 17, further comprising:

continuing the compaction until the number of the free blocks in the storage memory is equal to or larger than a third threshold value larger than the second threshold value, when the interval of the write commands from the host is equal to or larger than the predetermined value.

20. The method of claim 15, further comprising:

determining that the first data is the time-continuous data, when an interval of write commands from the host is smaller than a predetermined value.