Nonvolatile memory with independent access capability to associated buffer Number:7,334,080 from the United States Patent and Trademark Office (PTO) owispatent

Title: Nonvolatile memory with independent access capability to associated buffer

Abstract: A non-volatile storage device (1) has non-volatile memory units (FARY0 to FARY3), buffer units (BMRY0 to BMRY3) and a control unit (CNT), and the control unit can control a first access processing between an outside and the buffer unit and a second access processing between the non-volatile memory unit and the buffer unit upon receipt of directives from the outside separately from each other. The control unit can independently carry out an access control over the non-volatile memory unit and the buffer unit in accordance with the directives sent from the outside, respectively. Therefore, it is possible to set up next write data to the buffer unit simultaneously with the erase operation of the non-volatile memory unit or to output once read storage information to the buffer unit at a high speed as in a cache memory operation in accordance with the directive sent from the outside. Consequently, it is possible to reduce the overhead of a data transfer for reading/writing data from/to the non-volatile storage device.

Patent Number: 7,334,080 Issued on 02/19/2008 to Takase,   et al.

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Inventors:	Takase; Yoshinori (Tokyo, JP), Yoshida; Keiichi (Takarazuka, JP), Horii; Takashi (Higashimurayama, JP), Nozoe; Atsushi (Hino, JP), Tamura; Takayuki (Higashiyamato, JP), Fujisawa; Tomoyuki (Takarazuka, JP), Matsubara; Ken (Higashimurayama, JP)
Assignee:	Renesas Technology Corp. (Tokyo, JP) Hitachi ULSI Stystems Co., Ltd. (Tokyo, JP)
Appl. No.:	10/510,150
Filed:	November 15, 2002
PCT Filed:	November 15, 2002
PCT No.:	PCT/JP02/11953
371(c)(1),(2),(4) Date:	May 03, 2005
PCT Pub. No.:	WO03/085676
PCT Pub. Date:	October 16, 2003

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Foreign Application Priority Data

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Apr 05, 2002 [JP]			PCT/JP02/03417

Current U.S. Class:	711/103 ; 711/155
Current International Class:	G06F 12/00 (20060101)

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References Cited [Referenced By]

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U.S. Patent Documents

5297029	March 1994	Nakai et al.
5422856	June 1995	Sasaki et al.
6366977	April 2002	Mizoguchi
7080193	July 2006	Roohparvar
2004/0172499	September 2004	Roohparvar
2004/0177216	September 2004	Asari et al.
2005/0132129	June 2005	Venkiteswaran

Foreign Patent Documents

	5-282882		Oct., 1993		JP
	6-259320		Sep., 1994		JP
	11-85609		Mar., 1999		JP
	11-149788		Jun., 1999		JP
	2001-325796		Nov., 2001		JP

Primary Examiner: Nguyen; T
Attorney, Agent or Firm: Miles & Stockbridge P.C.

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Claims

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What is claimed is:

1. A non-volatile storage device comprising: a plurality of banks; and a control unit, wherein each bank has a non-volatile memory unit and a buffer unit corresponding thereto, the non-volatile memory unit of each bank can carry out an access operation independently, and the control unit is adapted to control, separately from each other, a first access processing between an outside of the non-volatile storage device and one of the buffer units and a second access processing between at least one non-volatile memory unit and the corresponding buffer unit, based upon receipt of a directive from the outside, the first access processing performing an access to one buffer unit, and the second access processing selectably performing one of an access to one non-volatile memory unit and an access to a plurality of non-volatile memory units.

2. The non-volatile storage device of claim 1, wherein the directive of the first access processing serves to write data input from the outside to the one buffer unit or to read data from the one buffer unit to the outside.

3. The non-volatile storage device of claim 2, wherein the directive for writing or the directive for reading is given by a change in one or a plurality of control signals input from the outside.

4. The non-volatile storage device of claim 3, wherein said non-volatile storage device can output, to the outside, state directive information for indicating that the second access processing is being carried out.

5. The non-volatile storage device of claim 1, wherein said directive of the second access processing is given in accordance with an access command which is one of a first access command for giving a directive to read data from the corresponding buffer unit and to write the data to the at least one non-volatile memory unit, a second access command for giving a directive to read data from the at least one non-volatile memory unit and to write the data to the corresponding buffer unit, or a third access command for giving a directive to erase data of the at least one non-volatile memory unit.

6. The non-volatile storage device of claim 1, wherein the control unit can recognize an address command supplied from the outside, and the control unit recognizes a specification of a storage region of one of the buffer units and a storage region of one of the non-volatile memory units in accordance with the address command.

7. The non-volatile storage device of claim 6, wherein said control unit recognizes a specification of one or a plurality of the buffer units in accordance with the address command, and gives an access to one or a plurality of the non-volatile memory units corresponding to one or a plurality of the buffer units specified in accordance with the address command through the second access processing.

8. The non-volatile storage device of claim 6, wherein the address command has first specification information, second specification information and third specification information, the first specification information specifying a non-volatile memory unit and tacitly specifying a buffer unit corresponding to the non-volatile memory unit thus specified, the second specification information specifying an accessing object address in the specified non-volatile memory unit, and the third specification information specifying an accessing object address of the specified buffer unit.

9. The non-volatile storage device of claim 8, wherein the control unit regards a specification of the buffer unit based on the first specification information as a specification of another buffer unit which does not correspond to the specified non-volatile memory unit when responding to a specific directive of the second access processing.

10. The non-volatile storage device of claim 1, wherein the control unit can carry out the second access processing of the at least one non-volatile memory unit and the first access processing of another buffer unit which does not correspond to the at least one non-volatile memory unit at the same time.

11. The non-volatile storage device of claim 1, wherein the control unit can carry out an erase processing of the at least one non-volatile memory unit and the first access processing of the one buffer unit at the same time.

12. The non-volatile storage device of claim 1, wherein the control unit maintains storage information of the buffer units in such a state as to carry out a processing of responding to a directive of the second access processing of reading data from the corresponding buffer unit and writing the data to the non-volatile memory unit and to then wait for another directive of the first access processing or the second access processing.

13. The non-volatile storage device of claim 1, wherein the control unit maintains storage information of the buffer units in such a state as to carry out a processing of responding to a directive of the first access processing of reading data from the one buffer unit and outputting the data to the outside and to then wait for another directive of the first access processing or the second access processing.

14. The non-volatile storage device of claim 11, wherein the control unit initializes storage information corresponding to one of the buffer units in accordance with a buffer clear command.

15. The non-volatile storage device of claim 12, wherein the control unit initializes storage information corresponding to the one buffer unit before writing data input from the outside to the one buffer unit in response to the first access processing when writing that data.

16. The non-volatile storage device of claim 1, wherein the control unit can transfer data read from the at least one non-volatile memory unit and written to the corresponding buffer unit through the second access processing at plural times in a different timing from data transfer from that buffer unit to the outside through the first access processing to be carried out at plural times.

17. The non-volatile storage device of claim 1, wherein the control unit omits a second access processing of writing data from the at least one non-volatile memory unit to the corresponding buffer unit which sets the same address as that on the at least one non-volatile memory unit of data retained in the corresponding buffer unit to be an access processing object when a directive of the second access processing is given.

18. The non-volatile storage device of claim 17, further comprising address holding means for holding address information about an address on the at least one non-volatile memory unit of the data retained in the corresponding buffer unit, and comparing means for comparing the address information held in the address holding means with address information about an address of the at least one non-volatile memory unit which is set to be a data reading object in the second access processing.

19. The non-volatile storage device of claim 17, wherein the control unit varies a period of a busy state depending on omission of the second access processing when a directive for outputting data from the one buffer unit to the outside is given through the first access processing.

20. The non-volatile storage device of claim 1, wherein the control unit can write data, written from the outside to the one buffer unit by the first access processing at plural times, from the one corresponding buffer unit to the corresponding non-volatile memory unit through the second access processing carried out at plural times.

21. The non-volatile storage device of claim 1, wherein the control unit can write data, rewritten from the outside to the one buffer unit by the first access processing carried out at plural times, from the one buffer unit to the corresponding non-volatile memory unit through the second access processing.

22. The non-volatile storage device of claim 1, wherein each non-volatile memory unit can store multivalued information of 2 bits or more in one storage element and each buffer unit can store binary information of 1 bit in one storage element.

23. The non-volatile storage device of claim 22, wherein the control unit can regard storage information of one or more of the non-volatile memory units as binary information and can control a third access processing of omitting a converting operation from a multivalue to a binary.

24. The non-volatile storage device of claim 5, further comprising, on a signal path to be used for the first access processing, an address buffer for latching address information sent from the outside, a buffer unit address buffer for inputting an output of the address buffer and supplying the output to the one buffer unit, a buffer unit data buffer for latching data output from the one buffer unit, and a data buffer for latching data output from the buffer unit data buffer and outputting the data to the outside, the control unit generating, as a dummy clock, a latch timing of the buffer unit address buffer and a latch timing of the buffer unit data buffer while an address command is recognized synchronously with a first strobe signal and a second strobe signal, for giving a directive to read data to the outside in the first access processing, is then changed.

25. The non-volatile storage device of claim 1, wherein the non-volatile memory unit has an erase unit which is plural times as large as a write unit and each of the buffer units has a storage capacity of the write unit, and the control unit uses both the corresponding buffer unit of a bank to be a rewrite object and the corresponding buffer unit of a different bank, in a save region of rewrite object storage information corresponding to a directive of a rewrite operation, for storage information of the erase unit.

26. The non-volatile storage device of claim 1, wherein said non-volatile storage device is formed on one semiconductor chip.

27. The non-volatile storage device of claim 1, further comprising another circuit module and wholly formed on one semiconductor chip.

28. A non-volatile storage device comprising: a plurality of memory banks; and a control unit, each memory bank having a non-volatile memory unit and a buffer unit corresponding thereto, access to object regions of the buffer unit and the non-volatile memory unit being specified based on an address command, the control unit being adapted to control, separately from each other, a first access processing operation between an outside of the non-volatile storage device and one of the buffer units and a second access processing operation between at least one non-volatile memory unit and the corresponding buffer unit, based upon receipt of directives from the outside, and the control unit further being adapted for controlling one first access processing in correspondence with second access processing, and for controlling a plurality of first access processings in correspondence with one second access processing.

29. The non-volatile storage device of claim 28, wherein the control unit utilizes the buffer unit corresponding to the memory bank specified in accordance with the address command in the first access processing, and utilizes the same buffer unit or the corresponding buffer unit of another memory bank according to contents of a directive in the second access processing.

30. The non-volatile storage device of claim 28, wherein the control unit controls a read set-up operation for an accessing object region of the non-volatile memory unit specified in accordance with an address command every time the address command is input within a limit based on the number of memory banks, and controls to read storage information from the non-volatile memory unit subjected to the read set-up and to write the storage information to the corresponding buffer unit when a read access command for giving a directive of a read operation as the second access processing is input.

31. The non-volatile storage device of claim 28, wherein the control unit controls a write operation for writing data to a corresponding buffer unit of a memory bank specified in accordance with an address command every time the address command is input and the data are input in accordance with a directive of the first access processing continuously within a limit based on the number of memory banks, and carries out a control to write the data possessed by the corresponding buffer unit to the non-volatile memory unit of the specified memory bank when a write access command giving a directive of the write operation as the second access processing is input.

32. The non-volatile storage device of claim 28, wherein the control unit controls an erase operation of a storage region for a corresponding non-volatile memory unit of a memory bank specified in accordance with an address command by inputting the address command and then inputting an erase command continuously within a limit based on the number of memory banks.

33. A non-volatile storage device comprising: a control unit; a non-volatile storage unit; and a buffer circuit, the non-volatile storage unit being divided into a plurality of non-volatile storage regions, the buffer circuit being divided into a plurality of buffer regions each corresponding to one of the non-volatile storage regions, the control unit accepting a plurality of operation directive commands from an outside of the non-volatile storage device, the operation directive commands having: a first operation directive command for giving a directive of an access operation between the buffer circuit and the outside; and a second operation directive command for giving a directive of an access operation between the buffer circuit and the non-volatile storage unit, the first operation directive command being for performing an access operation to one or a plurality of the buffer regions, and the second operation directive command being for performing an access operation to one or a plurality of the non-volatile storage regions.

34. The non-volatile storage device of claim 33, wherein the control unit has a command accepting state for accepting any of the operation directive commands, and accepts an arbitrary one of the operation directive commands to carry out processing corresponding to the accepted one operation directive command.

35. The non-volatile storage device of claim 34, wherein the operation directive commands further have a third operation directive command for specifying an address to select one of the non-volatile storage regions, and the second operation directive command gives a directive to carry out an access operation between one of the non-volatile storage regions, which is selected in accordance with the third operation directive command, and the buffer circuit.

36. The non-volatile storage device of claim 35, wherein the control unit selects one of the non-volatile storage regions in accordance with the third operation directive command and also selects one of the buffer regions corresponding to the selected non-volatile storage region, the first operation directive command gives a directive for carrying out an access operation between the one buffer region selected in accordance with the third operation directive command and the outside, and the second operation directive command gives a directive for carrying out an access operation between the one buffer region and the one non-volatile storage region, which are selected in accordance with the third operation directive command.

37. The non-volatile storage device of claim 36, wherein the control unit is brought into the command accepting state corresponding to a completion of a part of the access processing to a non-volatile storage region specified by the second operation directive command, and before all the access processings to the one non-volatile storage region are completed, can perform an acceptance of the third operation directive command, and an acceptance of the first or second operation directive command when the one buffer region and the one non-volatile storage region which are selected in accordance with the third operation directive command are different from the non-volatile storage region in which the access processing is carried out.

38. The non-volatile storage device of claim 37, wherein the first operation directive command includes a first write operation command for giving a directive to write data to the buffer circuit and a first read operation command for giving a directive to read data from the buffer circuit, and the second operation directive command includes a second write operation command for giving a directive to write data from the buffer circuit to the non-volatile storage unit and a second read operation command for giving a directive to read data from the non-volatile storage unit to the buffer circuit.

39. The non-volatile storage device of claim 38, wherein the first operation directive command further includes a first erase operation command for giving a directive to erase data written to the buffer circuit, and the second operation directive command further includes a second erase operation command for giving a directive to erase data written to the non-volatile storage unit.

40. The non-volatile storage device of claim 39, wherein after accepting the third operation directive command specifying a first non-volatile storage region of the non-volatile storage unit and then accepting the second erase operation command, and starting to erase data written to the first non-volatile storage region and before completing erasure of the data, the control unit can accept another third operation directive command specifying a second non-volatile storage region of the non-volatile storage unit and the first operation directive command or the second operation directive command.

41. The non-volatile storage device of claim 39, wherein after accepting the third operation directive command specifying a first non-volatile storage region of the non-volatile storage unit and then accepting the second read command, and completing to read data from the non-volatile storage unit to the buffer circuit, the control unit can accept the first operation directive command at least once, and furthermore, can carry out an operation for accepting the second write command.

42. The non-volatile storage device of claim 41, wherein after accepting the second read command and before accepting the second write command, the control unit carries out an acceptance of the other third operation directive command specifying a second non-volatile storage region of the non-volatile storage unit and an acceptance of the first operation directive command or the second operation directive command at least once and can then carry out an operation for accepting the third operation directive command specifying the first non-volatile storage region.

43. The non-volatile storage device of claim 38, wherein the control unit can carry out an operation for accepting the second write command after accepting the third operation directive command for specifying the first non-volatile storage region of the non-volatile storage unit and then accepting the first write command at least once.

44. The non-volatile storage device of claim 43, wherein the control unit can carry out an operation for accepting the first operation directive command at least once after accepting the first write command at least once.

45. The non-volatile storage device of claim 43, wherein the control unit can carry out the operation for accepting the second write command at least once after accepting the write command at least once.

46. The non-volatile storage device of claim 39, wherein the control unit accepts the second read command after accepting the third operation directive command for specifying a first address included in the first non-volatile storage region of the non-volatile storage unit, reads data in a first data volume from an address specified in accordance with the third operation directive command from the non-volatile storage unit to the buffer circuit in accordance with the second read command, and can then accept, at least once, the third operation directive command and the first operation directive, command which specify an address included in the first non-volatile storage region of the non-volatile storage unit and contained within a range of addresses of the first data volume.

47. The non-volatile storage device of claim 39, wherein when accepting the second read command after accepting the third operation directive command for specifying a first address included in the first non-volatile storage region of the non-volatile storage unit, reading data in a first data volume from an address specified in accordance with the third operation directive command from the non-volatile storage unit to the buffer circuit in accordance with the second read command, and further accepting the third operation directive command for specifying a second address included in the first non-volatile storage region of the non-volatile storage unit and contained within a range of addresses of the first data volume from the first address, and accepting the second read command, the control unit does not carry out a read operation from the non-volatile storage unit to the buffer circuit in a processing of the second read command.

48. The non-volatile storage device of claim 39, wherein the control unit does not erase data written to the buffer circuit in a completion of the second write command but erases the data written to the buffer circuit in accordance with the first erase operation command.

49. The non-volatile storage device of claim 35, further comprising a first buffer region of the buffer circuit which preferentially corresponds to a first non-volatile storage region and the second buffer region of a buffer circuit which preferentially corresponds to a second non-volatile storage region, the first buffer region being adapted to carry out an access operation together with the second non-volatile storage region, and the second buffer region being adapted to carry out an access operation together with the first non-volatile storage region.

50. The non-volatile storage device of claim 49, wherein the first operation directive command includes a first write operation command for carrying out an access operation between the first buffer region and the outside to give a directive to write data to the buffer circuit, a first read operation command for giving a directive to read data from the buffer circuit, and a first erase operation command for giving a directive to erase data written to the buffer circuit, and the second operation directive command includes a second write operation command for carrying out an access operation between a buffer region of the buffer circuit selected in accordance with the third operation directive command and the non-volatile storage unit to give a directive to write data from the buffer circuit to the non-volatile storage unit, a second read operation command for giving a directive to read data from the non-volatile storage unit to the buffer circuit, and a second erase operation command for giving a directive to erase data written to the non-volatile storage unit, the second write operation command having a main second write operation command for giving a directive to write data to the non-volatile storage region which preferentially corresponds to the buffer region of the buffer circuit which is selected, and a subordinate second write operation command for giving a directive to write data to a non-volatile storage region which is not the non-volatile storage region preferentially corresponding to the buffer region of the buffer circuit which is selected, and the second read operation command having a main second read operation command for giving a directive to read data from the non-volatile storage region which preferentially corresponds to the buffer region of the buffer circuit which is selected, and a subordinate second read operation command for giving a directive to read data from a non-volatile storage region which is not the non-volatile storage region preferentially corresponding to the buffer region of the buffer circuit which is selected.

51. The non-volatile storage device of claim 50, wherein data are read or written at a time on a first data volume unit in accordance with the second read command or the second write command, data are erased at a time on a unit of a second data volume which is larger than the first data volume in accordance with the second erase command, and when a first address is specified in accordance with the third operation directive command and a directive of the second erase command is given, first data included in an address range of the first data volume from the first are written to the non-volatile storage region preferentially corresponding to the buffer region of the buffer circuit which is selected and/or second data sent from a second address which is not included in the address range of the first data volume are written to the non-volatile storage region which is not the non-volatile storage region preferentially corresponding to the buffer region of the buffer circuit which is selected.

52. A non-volatile storage device comprising: a control unit; and a non-volatile storage unit, the non-volatile storage unit having a plurality of storage regions, and a plurality of buffer circuits each corresponding to one of the storage regions, the buffer circuits being connected to an outside of the non-volatile storage device, the buffer circuits being adapted to access the outside independently based on a control to be carried out by the control unit, and at least one of the storage regions being adapted to carry out an access operation independently with the corresponding buffer circuit based on the control to be carried out by the control unit.

53. A non-volatile storage device comprising: a non-volatile memory unit; a buffer unit; and a control unit, the non-volatile memory unit being divided into a plurality of memory banks each of which can independently carry out an access operation, the buffer unit being divided into a plurality of regions corresponding to the respective memory banks, and the control unit being adapted to independently carry out an access control in accordance with a directive given from an outside of the non-volatile storage device with respect to the non-volatile memory unit and the buffer unit, and giving an access directive to one or a plurality of the regions of the buffer unit in accordance with the directive given from the outside and then carrying out an access control between the non-volatile memory unit and the buffer unit with respect to one or a plurality of the memory banks corresponding to one or a plurality of the regions.

54. A non-volatile storage device comprising: a non-volatile memory unit; a buffer unit; and a control unit, the control unit being adapted to control, independently of each other, a first access processing between an outside of the non-volatile storage device and the buffer unit, a second access processing between the non-volatile memory unit and the buffer unit, and an initialization processing of the buffer unit upon receipt of directives from the outside, and carrying out no initialization on the buffer unit depending on a completion of the first access processing and the second access processing but bringing the buffer unit into an initialized state depending on the initialization processing of the buffer unit.

55. The non-volatile storage device of claim 54, wherein the non-volatile memory unit has a plurality of non-volatile memory cells, each of the non-volatile memory cells having a first state indicative of an erase state and a second state indicative of a write state, and wherein the initialized state of the buffer unit corresponds to the first state of the non-volatile memory cells.

56. The non-volatile storage device of claim 55, wherein each non-volatile memory cell has a threshold voltage, and the state of each non-volatile memory cell is determined depending on whether a threshold voltage of that non-volatile memory cell is included in an erase voltage distribution indicative of the erase state or a write voltage distribution indicative of the write state.

57. The non-volatile storage device of claim 56, wherein the second access processing includes a data read operation from the non-volatile memory unit to the buffer unit, the first access processing includes a data output operation from the buffer unit to the outside, and the data output operation can be carried out at plural times after one data read operation.

58. The non-volatile storage device of claim 57, wherein the control unit carries out the initialization processing of the buffer unit before the data read operation.

59. The non-volatile storage device of claim 56, wherein the second access processing includes a data write operation from the buffer unit to the non-volatile memory unit, the first access processing includes a data input operation from the outside to the buffer unit, and one data write operation can be carried out after the data input operation executed at plural times.

60. The non-volatile storage device of claim 59, wherein the control unit carries out the initialization processing of the buffer unit after the data write.

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Description

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CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from PCT international application PCT/JP02/11953 filed on Nov. 15, 2002, the content of which is hereby incorporated by reference into this application.

BACKGROUND OF THE INVENTION

The present invention relates to a non-volatile storage device having a non-volatile memory unit and a buffer unit thereof, and to an effective technology for an application to a flash memory having a multibank, for example.

BACKGROUND ART

JP-A-11-85609 has described a flash memory having a non-volatile memory unit and a buffer unit thereof. According to the publication, the memory unit can carry out read/write only on a unit of 8 bits or 16 bits, while it is necessary to exchange data on a unit of a single or plural sector(s) such as 512 bytes together with a host device, and therefore, the buffer unit is provided and utilized as a cache memory. The buffer unit to be utilized as the cache memory is simply used tacitly in an inner part when a command such as an erase, a program (hereinafter referred to also as a write) or a read for the flash memory is to be executed. In short, the buffer unit is not intended for a direct operation from the outside of the flash memory. In this respect, the inventor made considerations and found the following matters. First of all, the utilization of the buffer unit is not originally required in an erase operation for the non-volatile memory unit and cannot be applied to other uses. For this reason, an on-chip buffer unit cannot be effectively used practically during the erase operation. Moreover, the operation cannot be carried out in such a manner that storage information stored once in the buffer unit is to be read to an outside at a high speed independently of the operation of the non-volatile memory unit. In relation thereto, JP-A-6-259320 and JP-A-11-149788 have described a non-volatile storage device comprising a non-volatile memory unit and a buffer unit for holding data from an outside and serving to carry out such a control as to utilize the buffer unit as a cache memory. For a non-volatile storage device having a multibank, however, the inventor has found that there is room for further reducing the overhead of a data transfer between the outside and the flash memory in order to increase the speed of an access operation.

It is an object of the invention to provide a non-volatile storage device capable of effectively using a buffer unit practically during an erase operation for a non-volatile memory unit.

It is another object of the invention to provide a non-volatile storage device capable of quickly reading storage information read from the non-volatile memory unit and retained in the buffer unit to an outside independently of the operation of the non-volatile memory unit.

It is a further object of the invention to provide a non-volatile storage device capable of reducing the overhead of a data transfer between the outside and the no-volatile memory unit.

The above and other objects and novel features of the invention will be apparent from the following description of the specification and the accompanying drawings.

SUMMARY OF THE INVENTION

[1] <<Independent Access Control>> A non-volatile storage device according to the invention has a plurality of banks (BNK0 to BNK3) and a control unit (CNT), wherein the banks (BNK0 to BNK3) have non-volatile memory units (FARY0 to FARY3) and buffer units (BMRY0 to BMRY3) corresponding thereto. The non-volatile memory unit of each bank can be caused to carry out an access operation independently. The control unit can carry out a control upon receipt of a directive (22, 23) of a first access processing between an outside and the buffer unit and a directive (21, 24) of a second access processing between the non-volatile memory unit and the buffer unit from the outside separately from each other. The first access processing includes an access to one buffer unit, and the second access processing includes an access to one non-volatile memory unit and an access to a plurality of non-volatile memory units and can be caused to select either of the accesses.

As described above, the control unit can carry out the access control over the non-volatile memory unit having a multibank and the buffer unit independently in accordance with the directives sent from an outside, respectively. Therefore, the non-volatile memory unit and the buffer unit can be operated in parallel and storage information read once onto the buffer unit can be output at a high speed as in the operation of a cache memory in accordance with a directive sent from the outside. Consequently, it is possible to reduce the overhead of a data transfer for reading/writing data from/to the non-volatile storage device having the multibank.

<<First Access Processing>> In a specific manner according to the invention, the directive of the first access processing serves to store (hereinafter referred to also as a write) data input from the outside to the buffer unit or to read data from the buffer unit to the outside. The directive for writing or the directive for reading is given by a change in one or a plurality of control signals (CLE, ALE, WEb, REb) input from the outside, for example. More specifically, the directive for writing is given in a write enable state in command latch disable and address latch disable. Moreover, the directive for reading is given in a read enable state in the command latch disable and the address latch disable. The state of a control signal such as the single or plural strobe signals can also be regarded as a command code. It is also possible to employ a different command code from the strobe signal for the directive of the first access processing.

In a specific manner according to the invention, state directive information (R/Bb) for indicating that the second access processing is being carried out is output to the outside. It is possible to easily control the directive timing of the read enable or the write enable which is sent from the outside.

<<Second Access Processing>> In a specific manner according to the invention, the directive of the second access processing is given in accordance with an access command. The access command has a first access command for giving a directive to read data from the buffer unit and to write the data to the non-volatile memory unit, a second access command for giving a directive to read the data from the non-volatile memory unit and to write the data to the buffer unit, or a third access command for giving a directive to erase the data of the non-volatile memory unit. In the invention, a word of write can be replaced with a word of store when a volatile memory unit such as a buffer unit is caused to hold information, and furthermore, can be replaced with a word of program when the non-volatile memory unit is caused to hold the information.

<<Plural Memory Banks>> In a specific manner according to the invention, the non-volatile memory unit and the buffer unit are caused to correspond to each other and plural sets of correspondences are provided as memory banks.

<<Address Command>> An address command (20) is employed for specifying an access address at this time, for example. The control unit can recognize an address command supplied from the outside, and the address command can specify a storage region of the buffer unit and a storage region of the non-volatile memory unit.

As a specific example, the address command can have first specification information, second specification information and third specification information. The first specification information specifies a non-volatile memory unit and tacitly specifies a buffer unit corresponding to the non-volatile memory unit thus specified. The second specification information specifies an accessing object address in the non-volatile memory unit which is specified. The third specification information specifies an accessing object address in the buffer unit which is specified.

Attention is paid to the utilization efficiency of the buffer unit. While the buffer unit can be specified freely in the first access processing, the buffer unit corresponding to the non-volatile memory unit is specified tacitly in the second access processing. In order to expand the specification, it is preferable that the control unit should regard the specification of the buffer unit based on the first specification information as the specification of another buffer unit which does not correspond to the non-volatile memory unit when responding to the specific directive of the second access processing.

<<Parallelization of First Access Processing and Second Access Processing>> In a specific manner according to the invention, the control unit can carry out the second access processing of the non-volatile memory unit and the first access processing of another buffer unit which does not correspond to the non-volatile memory unit at the same time depending on the directive states of the first and second access processings. Moreover, the control unit can carry out an erase processing of the non-volatile memory unit and the first access processing of the buffer unit at the same time. For example, during the erase operation of the non-volatile memory unit, write data are input to the buffer unit corresponding to the non-volatile memory unit. In short, during the access operation of the non-volatile memory unit, data to be used next are input to the buffer unit on a background thereof.

<<Maintenance of Storage Data of Buffer Unit>> When taking a different viewpoint of the parallelization of the access processing, the control unit maintains storage information of the buffer unit in such a state as to carry out a processing of responding to a directive of the second access processing of reading data from the buffer unit and writing the data to the non-volatile memory unit and to then wait for another directive of the first access processing or the second access processing. In the case in which the storage information held by the buffer unit are to be copied onto another place of the non-volatile memory unit or a retrial for a write error is to be carried out, consequently, the invention is convenient. Moreover, the control unit maintains storage information of the buffer unit in such a state as to carry out a processing of responding to a directive of the first access processing of reading data from the buffer unit and outputting the data to an outside and to then wait for another directive of the first access processing or the second access processing. Consequently, the storage information read once to the buffer unit can be output at a high speed as in the operation of a cache memory in accordance with a directive sent from the outside.

The control unit initializes storage information of the buffer unit in accordance with a buffer clear command in such a manner that unnecessary data can be deleted when the storage information is to be maintained in the buffer unit. In order to prevent unnecessary data remaining in the buffer unit from being written erroneously in the write, moreover, the storage information of the buffer unit is initialized before the write of data input from the outside to the buffer unit when the write is to be carried out in response to the first access processing.

<<Read Cache Operation of Buffer Unit>> In a specific manner according to the invention, the control unit can transfer data read from the non-volatile memory unit and written to the buffer unit through the second access processing at plural times in a different timing from the buffer unit to the outside through the first access processing to be carried out at plural times which is designated from the outside. Consequently, the buffer unit can be caused to carry out a read cache operation by a control sent from the outside.

Moreover, the control unit omits a second access processing of writing data from the non-volatile memory unit to the buffer unit which sets the same address as that on the non-volatile memory unit of data retained in the buffer unit to be an access processing object when a directive of the second access processing is given. Consequently, the non-volatile storage device can carry out an address comparison by itself, thereby causing the buffer unit to perform the read cache operation. For the address comparing operation, for example, there are provided address holding means for holding address information about an address on the non-volatile memory unit of the data retained in the buffer unit, and comparing means for comparing the address information held in the address holding means with address information about an address of the non-volatile memory unit which is set to be a data reading object in the second access processing.

The read cache operation control of the buffer unit by the control unit is equivalent to a control for varying a period of a busy state based on a signal indicating, as the busy state, that the second access processing is being carried out depending on presence of the omission of the second access processing when a directive for outputting data written from the non-volatile memory unit to the buffer unit in the second access processing from the buffer unit to the outside is given through the first access processing.

<<Copy and Rewrite of Utilization of Buffer Unit>> In a specific manner according to the invention, the control unit can write data written from the outside to the buffer unit by the first access processing at plural times from the buffer unit to the non-volatile memory unit through the second access processing carried out at plural times. Consequently, it is possible to efficiently carry out copy and write retrial processings.

<<Decision of Write Data over Buffer Unit>> In a specific manner according to the invention, the control unit can write data rewritten from the outside onto the buffer unit by the first access processing carried out at plural times from the buffer unit to the non-volatile memory unit through the second access processing. For example, a processing efficiency can be enhanced when a read/modify/write operation is to be repeated many times for the same sector data.

<<Binary Mode>> In a specific manner according to the invention, the non-volatile memory unit can store multivalued information of 2 bits or more in one storage element and the buffer unit can store binary information of 1 bit in one storage element. At this time, the control unit can regard storage information of the non-volatile memory unit as binary information and can control a third access processing of omitting a converting operation from a multivalue to a binary. Consequently, a time required for reading data to an outside is shortened. If the object of the third access processing is set to be management domain data for the sector of file data, for example, it is possible to quickly decide the presence of the validity or alternative of a sector, thereby contributing to an increase in the speed of a file access.

<<Independent Clock Generation>> In a specific manner according to the invention, there is provided, on a signal path to be used for the first access processing, an address buffer for latching address information sent from the outside, a buffer unit address buffer for inputting an output of the address buffer and supplying the output to the buffer unit, a buffer unit data buffer for latching data output from the buffer unit, and a data buffer for latching data output from the buffer unit data buffer and outputting the data to the outside. Attention is paid to the structure in which a comparatively large number of pipeline stages from the address input to the data output are provided. At this time, the control unit independently generates a clock and creates a latch timing of the buffer unit address buffer and a latch timing of the buffer unit data buffer while an address command is recognized synchronously with a first strobe signal and a second strobe signal for giving a directive to read data to the outside in the first access processing is then changed. Even if the number of the pipeline stages from the address input to the data output is comparatively large, a countermeasure can be taken.

<<Rewrite Operation>> In a specific manner according to the invention, when there are provided plural sets of non-volatile memory units and buffer units corresponding to each other, an erase unit of the non-volatile memory unit is plural times as large as a write unit and each of the buffer units has a storage capacity on the write unit, the control unit uses both the non-volatile memory unit to be a rewrite object and the buffer unit of a different non-volatile memory unit in a save region of rewrite object storage information corresponding to a directive of a rewrite operation for storage information on the erase unit. Also in the case in which an erase unit for the non-volatile memory unit is greater than a write unit, consequently, the rewrite can be carried out.

<<LSI>> In a specific manner according to the invention, the non-volatile storage device is constituted as a memory LSI formed on one semiconductor chip, a microcomputer LSI formed on one semiconductor chip together with other circuit modules such as a CPU or a system LSI.

[2] <<Independent Access Control>> A non-volatile storage device according to another aspect of the invention comprises a plurality of memory banks (BNK0 to BNK3) and a control unit (CNT), and the memory banks have non-volatile memory units (FARY0 to FARY3) and buffer units (BMRY0 to BMRY3). Accessing object regions of the buffer unit and the non-volatile memory unit are specified based on an address command (20). The control unit can carry out a control upon receipt of a directive (22, 23) of a first access processing between an outside and the buffer unit and a directive (21, 24) of a second access processing between the non-volatile memory unit and the buffer unit from the outside separately from each other. Furthermore, the control unit can control one of the first access processing corresponding to one of the second access processing and can control a plurality of the first access processings corresponding to one of the second access processing.

As described above, the control unit can carry out an access control over the non-volatile memory unit and the buffer unit independently in accordance with directives sent from an outside, respectively. Therefore, the non-volatile memory unit and the buffer unit can be operated in parallel and storage information read once onto the buffer unit can be output at a high speed as in the operation of a cache memory in accordance with a directive sent from the outside.

The control unit is caused to utilize the buffer unit of the memory bank specified in accordance with the address command in the first access processing, and can freely specify the buffer unit in the first access processing. In the second access processing, the control unit is caused to utilize the buffer unit of the memory bank specified in accordance with the address command or the buffer unit of another memory bank corresponding to contents of a directive in the second access processing.

<<Multibank Read>> In a specific manner according to the invention, the control unit controls a read set-up operation for the accessing object region of the non-volatile memory unit specified in accordance with an address command every time the address command is input within a limit of the number of times of a dependence on the number of the memory banks, and controls to read storage information from the non-volatile memory unit subjected to the read set-up and to write the storage information to the buffer unit when a read access command for giving a directive of a read operation as the second access processing is input. Consequently, it is possible to carry out a read operation for a multibank.

<<Multibank Write>> In a specific manner according to the invention, the control unit controls a write operation for write data to the buffer unit of the memory bank specified in accordance with an address command every time the address command is input and write data are input in accordance with a directive of the first access processing continuously within a limit of the number of times of a dependence on the number of the memory banks, and carries out a control to write the write data possessed by the buffer unit to the non-volatile memory unit of the corresponding memory bank when a write access command for giving a directive of the write operation as the second access processing is input. Consequently, it is possible to carry out a write operation for a multibank.

<<Multibank Erase>> In a specific manner according to the invention, the control unit controls an erase operation of a storage region for the non-volatile memory unit of the memory bank specified in accordance with an address command by inputting the address command and then inputting an erase command continuously within a limit of the number of times of a dependence on the number of the memory banks. Consequently, it is possible to carry out an erase operation for a multibank.

[3] <<Independent Access Control>> A non-volatile storage device according to a further aspect of the invention has a control unit, a non-volatile storage unit and a buffer circuit, the non-volatile storage unit being divided into a plurality of non-volatile storage regions, and the buffer circuit being divided into a plurality of buffer regions corresponding to the non-volatile storage regions. The control unit accepts a plurality of operation directive commands from an outside. The operation directive commands have a first operation directive command (22, 23) for giving a directive of an access operation between the buffer circuit and the outside and a second operation directive command (21, 24) for giving a directive of an access operation between the buffer circuit and the non-volatile storage unit. The first operation directive command can give a directive of an access operation to the buffer region, and the second operation directive command can select either an access operation to one of the non-volatile storage region or an access operation to a plurality of the non-volatile storage regions, thereby giving a directive.

The control unit has a command accepting state capable of accepting the operation directive command, and accepts the operation directive command to carry out a processing corresponding to each operation directive command and then brings the command accepting state.

<<Address Command>> In a specific manner according to the invention, the non-volatile storage unit is divided into a plurality of storage regions, the operation directive command has a third operation directive command (20) for specifying an address to select one of the storage regions of the non-volatile storage unit, and the second operation directive command gives a directive to carry out an access operation between the storage region of the non-volatile storage unit which is selected in accordance with the third operation directive command and the buffer circuit.

<<Multibank>> The buffer circuit is divided into a plurality of regions corresponding to the storage regions. At this time, the control unit selects the storage region of the non-volatile storage unit in accordance with the third operation directive command and also selects the region of the buffer circuit corresponding to the storage region of the non-volatile storage unit thus selected. The first operation directive command gives a directive for carrying out an access operation between the region of the buffer circuit selected in accordance with the third operation directive command and the outside. The second operation directive command gives a directive for carrying out an access operation between the region of the buffer circuit and the storage region of the non-volatile storage unit which are selected in accordance with the third operation directive command.

<<Parallelization Processing of Multibank>> The control unit is brought into the command accepting state corresponding to a completion of a part of the access processing to one of the storage regions of the non-volatile storage unit in accordance with the second operation directive command, and before all the access processings to one of the storage regions are completed, can carry out an acceptance of the third operation directive command, and an acceptance of the first or second operation directive command when the buffer circuit region and the storage region of the non-volatile storage unit which are selected in accordance with the third operation directive command are different from the region in which the access processing is carried out.

<<Write/Read Operation Directive Command>> The first operation directive command includes a first write operation command for giving a directive to write data to the buffer circuit and a first read operation command for giving a directive to read data from the buffer circuit, for example. The second operation directive command includes a second write operation command for giving a directive to write data from the buffer circuit to the non-volatile storage unit and a second read operation command for giving a directive to read data from the non-volatile storage unit to the buffer circuit, for example.

<<Erase Operation Directive Command>> The first operation directive command further includes a first erase operation command for giving a directive to erase data written to the buffer circuit. The second operation directive command further includes a second erase operation command for giving a directive to erase data written to the non-volatile storage unit.

<<Command Acceptance parallelized with Erase>> After accepting the third operation directive command for specifying a first storage region of the non-volatile storage unit and then accepting the second erase operation command, and starting to erase data written to the first storage region and before completing the erase of the data, it is possible to accept the third operation directive command for specifying a second storage region of the non-volatile storage unit and the first operation directive command or the second operation directive command.

<<Decision of Write Data over Buffer Circuit>> After accepting the third operation directive command for specifying a first storage region of the non-volatile storage unit and then accepting the second read command, and completing to read data from the non-volatile storage unit to the buffer circuit, it is possible to accept the first operation directive command at least once, and furthermore, to carry out an operation for accepting the second write command.

<<Parallelization Processing>> After accepting the second read command and before accepting the second write command, it is possible to carry out an acceptance of the third operation directive command for specifying a second storage region of the non-volatile storage unit and an acceptance of the first operation directive command or the second operation directive command at least once and to then carry out an operation for accepting the third operation directive command for specifying the first storage region.

<<Decision of Write Data over Buffer Circuit>> It is possible to carr