Patent Publication Number: US-8533560-B2

Title: Controller, data storage device and program product

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2011-044425, filed on Mar. 1, 2011; the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to a controller, a data storage device and a program product. 
     BACKGROUND 
     A data storage device is typically required to be set so as to perform, instead of a normal response sending user data, a predetermined response in response to a readout request for a certain logical block address (LBA) from a host device. In general, a data storage device is designed to perform a normal response in response to a readout request for a certain logical block address unless it is set to perform a predetermined response. However, with the configuration in which the setting for a logical block address is always checked before performing a normal response, it takes a long response time for the normal response. Here, it may be considered to perform reading out of user data from a recording medium and checking of the setting for a logical block address in parallel. In this case, however, it is still necessary to wait for the check result of the setting for the logical block address before sending the user data to the host device. Therefore, the response time for the normal response may be depended on the time for checking the setting for the logical block address and may become longer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram showing a schematic configuration of a data storage device according to a first embodiment; 
         FIG. 2  illustrates an example of a storage area according to the first embodiment; 
         FIG. 3A  illustrates an example of manipulation target data containing an error detecting code according to the first embodiment; 
         FIG. 3B  illustrates an example of recovery manipulation target data resulting from bit string manipulation according to the first embodiment; 
         FIG. 3C  illustrates an example of recovered data resulting from bit string recovery manipulation according to the first embodiment; 
         FIG. 4A  illustrates an example of manipulation target data containing an error correcting code according to the first embodiment; 
         FIG. 4B  illustrates an example of recovery manipulation target data resulting from bit string manipulation according to the first embodiment; 
         FIG. 4C  illustrates an example of recovered data resulting from bit string recovery manipulation according to the first embodiment; 
         FIG. 5  illustrates an example of special data containing a magic number according to the first embodiment; 
         FIG. 6  illustrates an example of a writing process according to the first embodiment; 
         FIG. 7  illustrates an example of a special data setting process according to the first embodiment; 
         FIG. 8  illustrates an example of a readout process according to the first embodiment; 
         FIG. 9  is a diagram showing a schematic configuration of a data storage device according to a second embodiment; 
         FIG. 10  illustrates an example of a storage area according to the second embodiment; 
         FIG. 11  illustrates an example of a writing process according to the second embodiment; 
         FIG. 12  illustrates an example of a special data setting process according to the second embodiment; and 
         FIG. 13  illustrates an example of a readout process according to the second embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, a controller includes a bit string manipulating unit and a special data setting unit. The bit string manipulating unit manipulates a bit string of manipulation target data based on a predetermined rule. The special data setting unit generates a magic number based on a special data setting request from a host interface, obtains an error detecting code for the magic number, and sends the magic number and the error detecting code as manipulation target data to the bit string manipulating unit to obtain a manipulated manipulation target data. The special data setting unit also extracts logical block address information from the special data setting request, and instructs an access unit to write the magic number in the manipulated manipulation target data to a user data storage area and to write the error detecting code in the manipulated manipulation target data to a redundant area in a storage area located by the logical block address information. 
     A controller, a data storage device and a program according to exemplary embodiments will be described below in detail with reference to the drawings. 
     First Embodiment 
     Configuration 
     In a first embodiment, a controller, a data storage device and a program will be exemplified.  FIG. 1  illustrates a schematic configuration of a data storage device  100  according to the first embodiment. As illustrated in  FIG. 1 , the data storage device  100  includes a controller  110 , a first generating unit  121 , a first determining unit  122 , a host interface  130 , an access unit  150 , and a storage unit  160 . The controller  110  includes a bit string manipulating unit  111 , a bit string recovering unit  112 , a special data setting unit  113 , a writing unit  114  and a readout unit  115 . The controller  110  is interconnected with the access unit  150  and the host interface  130  via a data bus  140 , for example. In the following description, special data refer to data for performing a predetermined response including a transmission of a predetermined acknowledge to a host device. 
     The storage unit  160  has a plurality of storage areas. Data associated with each logical block address of the data storage device  100  are stored in each of the storage areas. Note that, in the first embodiment, the logical block addresses of the data storage device  100  may be associated with physical addresses (physical block addresses) of the storage areas in the storage unit  160  in any form. For example, the logical block addresses and the physical block addresses may be statically fixed, or the associations between the logical block addresses and the physical block addresses may be managed by an address translation table. The address translation table can be dynamically modified at predetermined timings. 
       FIG. 2  illustrates an example of a storage area in the storage unit  160 . As illustrated in  FIG. 2 , each storage area  161  includes a user data storage area  162  in which user data are stored and a redundant area  163  in which redundant data are stored. The redundant data may be an error detecting code or an error correcting code, for example. 
     The access unit  150  supports a writing process and a readout process to/from the storage unit  160  performed by the controller  110 . The host interface  130  performs an interface process between the data storage device  100  and the host device (not illustrated). 
     More specifically, the host interface  130  receives a setting request for a logical block address from the host device. The setting request requests to set a predetermined response instead of a normal response with user data when a readout request for a logical block address of the data storage device  100  is issued by the host device. Herein, the setting request is referred to as a special data setting request. The special data setting request includes logical block address information and special data identification information for identifying the type of the predetermined response, for example. Upon receiving the special data setting request from the host device, the host interface  130  sends the received special data setting request to the special data setting unit  113 . 
     The host interface  130  also receives a write request from the host device. The write request includes logical block address information of a storage area to write to and data to be written (hereinafter referred to as write target data), for example. Upon receiving the write request from the host device, the host interface  130  sends the received write request to the writing unit  114 . 
     Furthermore, the host interface  130  receives a readout request from the host device. The readout request includes logical block address information of a storage area to read out from, for example. Upon receiving the readout request from the host device, the host interface  130  sends the received readout request to the readout unit  115 . In addition, upon receiving a readout acknowledge from the readout unit  115  in response to the readout request, the host interface  130  sends the received readout acknowledge to the host device. The readout acknowledge includes readout target data requested by the host device or readout state information. The readout state information is information indicating a readout state. The information indicating a readout state may be information indicating a readout error, for example. 
     The first generating unit  121  receives data from which an error detecting code is generated from a request source of the error detecting code. The request source of the error detecting code may be the special data setting unit  113 , the writing unit  114 , or the like. The first generating unit  121  generates an error detecting code from the received data based on a predetermined method. The first generating unit  121  then sends the generated error detecting code to the request source. Note that the error detecting code may be replaced with an error correcting code herein. 
     The first determining unit  122  receives error detection target data and an error detecting code associated therewith from a request source of error determination. The request source of the error determination may be the readout unit  115 , for example. The first determining unit  122  performs an error determination process of determining whether or not an error is present in the received error detection target data and error detecting code based on a predetermined method. The first determining unit  122  then sends the result of the error determination process to the request source. When the error detecting code is replaced with the error correcting code, the error determination process is replaced with “an error determination process of determining whether or not error correction of the received error correction target data and error correcting code is possible based on a predetermined method”. 
     The bit string manipulating unit  111  receives manipulation target data from a request source of bit string manipulation. The manipulation target data include special data associated with a predetermined response and an error detecting code associated with the bit string of the special data, for example. The request source of the bit string manipulation may be the special data setting unit  113 , for example. The bit string manipulating unit  111  performs a bit string manipulation process of manipulating the bit string of the received manipulation target data according to a predetermined rule. The predetermined rule can be a rule of bit string manipulation resulting in error detection, and also a rule of bit string manipulation that allows a bit string resulting from the bit string manipulation to be recovered to the original bit string. An example of the predetermined rule may be inverting a predetermined bit value (0 or 1). However, the predetermined rule is not limited thereto. The bit string manipulating unit  111  then sends the manipulation target data resulting from the bit string manipulation to the request source. When the error detecting code is replaced with the error correcting code, the predetermined rule can be a rule “making error correction of a bit string resulting from the bit string manipulation impossible and allowing the bit string resulting from the bit string manipulation to be recovered to the original bit string”. An example of the predetermined rule may be inverting a predetermined bit value (0 or 1) for the number of bits in excess of the error correcting capability. However, the predetermined rule is not limited thereto. 
     The bit string recovering unit  112  receives recovery manipulation target data from a request source of the bit string recovery manipulation. The request source of the bit string recovery manipulation may be the readout unit  115 , for example. The recovery manipulation target data are manipulation target data resulting from the bit string manipulation, for example. Specifically, the recovery manipulation target data include special data resulting from the bit string manipulation and the error detecting code. The bit string recovering unit  112  performs a bit string recovery manipulation process of applying recovery manipulation to the bit string of the recovery manipulation target data according to a predetermined rule. The bit string recovery manipulation refers to recovery of the bit string of recovery manipulation target data to an original state before the bit string manipulation if the bit string results from manipulation by the bit string manipulating unit  111 . If the bit string manipulation process is as the aforementioned example (inverting a predetermined bit value), the bit string recovery manipulation process can be inverting the predetermined bit value once again. As a result, the bit string resulting from the bit string manipulation can be recovered to the original bit string. Note that the bit string recovery manipulation process can be modified in various manners depending on the bit string manipulation process performed by the bit string manipulating unit  111 . The bit string recovering unit  112  then sends the recovery manipulation target data resulting from the bit string recovery manipulation to the request source. When the error detecting code is replaced with the error correcting code, the predetermined bit value is inverted once again for the number of bits in excess of the error correcting capability in the bit string recovery manipulation process corresponding to the example of inverting the predetermined bit value for the number of bits in excess of the error correcting capability in the bit string manipulation process. As a result, the bit string resulting from the bit string manipulation can be recovered to the original bit string. 
     Specific examples of a series of processes from the bit string manipulation to the bit string recovery manipulation will be described in detail referring to  FIGS. 3A to 4C . As described above, the processes of the bit string manipulation and the bit string recovery manipulation are not limited to the specific examples described below. 
     First, a specific example of a series of processes from the bit string manipulation to the bit string recovery manipulation using an error detecting code will be described referring to  FIGS. 3A to 3C .  FIG. 3A  illustrates an example of manipulation target data. As illustrated in  FIG. 3A , manipulation target data  11  include special data  12  having a bit length equal to the length of the user data storage area  162  of the storage area  161  in the storage unit  160  and an error detecting code  13  that is composed of several lower bits, for example. The error detecting code  13  is a value generated from the special data  12  based on a predetermined method. 
     In the bit string manipulation process, upon receiving the manipulation target data  11  ( FIG. 3A ) from the request source, the bit string manipulating unit  111  inverts the value of a predetermined bit (second lowest bit  13   a , for example) thereof. As a result, recovery manipulation target data  11 A in which a correct error detecting code  13  has been changed to an error detecting code  13 A including an error are obtained as illustrated in  FIG. 3B . The number of bits to be manipulated may be more than one. Moreover, data to be input to the bit string manipulating unit  111  may be at least one of the special data  12  and the error detecting code  13  in the manipulation target data  11 . In other words, the bit string to be manipulated may be at least one of the special data  12  and the error detecting code  13 , and only the bit string to be manipulated needs to be input to the bit string manipulating unit  111 . 
     In the bit string recovery manipulation process, on the other hand, upon receiving the recovery manipulation target data  11 A as illustrated in  FIG. 3B , the bit string recovering unit  112  inverts the value of the predetermined bit  13   a  thereof again. As a result, recovered data  11 B in which the value of the predetermined bit  13   a  has been recovered are obtained as illustrated in  FIG. 3C . As is apparent by comparing  FIGS. 3A and 3C , the bit string of the recovered data  11 B ( FIG. 3C ) is the same as that of the manipulation target data  11  ( FIG. 3A ). Specifically, as a result of the bit string recovery manipulation process, the bit string of the recovery manipulation target data  11 A is restored to the bit string of the manipulation target data  11  before the bit string manipulation. Note that the data to be input to the bit string recovering unit  112  only need to be a bit string of at least one of the special data  12  and the error detecting code  13  that is manipulation target. 
     While the bit string of the error detecting code  13  is manipulation target in this specific example, the manipulation target is not limited thereto. For example, the bit string of the special data  12  may be the manipulation target. Alternatively, both the bit string of the error detecting code  13  and the bit string of the special data  12  may be manipulation target. In other words, modifications can be made in any manner as long as an error is detected when the recovery manipulation target data  11 A resulting from the bit string manipulation are input to the first determining unit  122 , and no error is detected (i.e., data are correct) when the recovered data  11 B resulting from the bit string recovery manipulation are input to the first determining unit  122 . 
     Next, a specific example of a series of processes from the bit string manipulation to the bit string recovery manipulation using an error correcting code will be described referring to  FIGS. 4A to 4C .  FIG. 4A  illustrates an example of manipulation target data. As illustrated in  FIG. 4A , manipulation target data  21  include special data  12  and an error correcting code  23  that is composed of several lower bits. The error correcting code  23  is a value generated from the special data  12  based on a predetermined method. 
     In the bit string manipulation process, upon receiving the manipulation target data  21  ( FIG. 4A ) from the request source, the bit string manipulating unit  111  inverts values of predetermined bits (second to fourth lowest bits  23   a , for example) of the bit string thereof for the number of the predetermined bits in excess of the error correcting capability. As a result, recovery manipulation target data  21 A in which a correct error correcting code  23  has been changed to an error correcting code  23 A including an error in excess of the error correcting capability are obtained as illustrated in  FIG. 4B . Note that data to be input to the bit string manipulating unit  111  may be at least one of the special data  12  and the error correcting code  23  in the manipulation target data  21 . In other words, the bit string to be manipulated may be at least one of the special data  12  and the error correcting code  23 , and only the bit string to be manipulated needs to be input to the bit string manipulating unit  111 . 
     In the bit string recovery manipulation process, on the other hand, upon receiving the recovery manipulation target data  21 A as illustrated in  FIG. 4B , the bit string recovering unit  112  inverts the values of the predetermined bits  23   a  thereof again. As a result, recovered data  21 B in which the values of the predetermined bits  23   a  have been recovered are obtained as illustrated in  FIG. 4C . As is apparent by comparing  FIGS. 4A and 4C , the bit string of the recovered data  21 B ( FIG. 4C ) is the same as that of the manipulation target data  21  ( FIG. 4A ). Specifically, as a result of the bit string recovery manipulation process, the bit string of the recovery manipulation target data  21 A is restored to the bit string of the manipulation target data  21  before the bit string manipulation. Note that data to be input to the bit string recovering unit  112  only need to be a bit string of at least one of the special data  12  and the error correcting code  23  that is manipulation target. 
     This specific example exemplifies a case in which the error correcting capability is two bits and the values of three bits in excess thereof are inverted. In this case, the bit string of the error correcting code  23  is also manipulation target as in the case of the error detecting code  13 . However, the manipulation target is not limited thereto. For example, the bit string of the special data  12  may be the manipulation target. Alternatively, both the bit string of the error correcting code  23  and the bit string of the special data  12  may be manipulation target. In other words, modifications can be made in any manner as long as error correction is not possible when the manipulated data  21 A resulting from the bit string manipulation are input to the first determining unit  122 , and error correction is possible when the recovered data  21 B resulting from the bit string recovery manipulation are input to the first determining unit  122 . 
     The description refers back to  FIG. 1 . The writing unit  114  receives a write request from the host interface  130 . The writing unit  114  extracts write target data from the received write request. The writing unit  114  then sends the extracted write target data to the first generating unit  121 , and obtains an error detecting code associated with the write target data. The data to be sent to the first generating unit  121  may further include data other than the write target data. For example, the data to be sent to the first generating unit  121  may further include a bit string indicating logical block address information extracted from the received write request and a predetermined bit string. 
     The writing unit  114  extracts the logical block address information of a storage area to write to from the received write request. The writing unit  114  instructs the access unit  150  to write the write target data and the error detecting code to the storage area  161  in the storage unit  160  associated with the extracted logical block address information. 
     The special data setting unit  113  receives a special data setting request from the host interface  130 . The special data setting unit  113  extracts special data identification information for identifying the type of the predetermined response from the special data setting request. The special data setting unit  113  also generates special data including an identification bit string that is a bit string corresponding to the extracted type of the predetermined response. 
     The identification bit string refers to a bit string associated uniquely with each of a plurality of types of response. The identification bit string is also called a magic number. The identification bit string allows a specific target (specific type of response) to be identified uniquely from a plurality of targets to be identified (a plurality of types of response). 
       FIG. 5  illustrates an example of special data including a magic number. As illustrated in  FIG. 5 , special data  32  are composed of a bit string having the same size as the user data storage area  162  in the storage area  161  illustrated in  FIG. 2 . If the type of the predetermined response can be expressed by three bits, the upper three bits of the special data  32  are used for the magic number  32   a , for example. The remaining bits of the special data  32  may be all “0” constituting NULL data  32   b . Alternatively, the special data  32  may be modified in various manners as long as the special data  32  can be composed of values that can be managed or predicted by the controller  110 . 
     The description refers back to  FIG. 1 . The special data setting unit  113  sends the generated special data  32  to the first generating unit  121  and obtains an error detecting code associated with the bit string of the special data  32 . The data sent to the first generating unit  121  may further include data other than the special data  32 . For example, the data may further include a bit string indicating logical block address information extracted from the received special data setting request and a predetermined bit string. 
     The special data setting unit  113  also sends the special data  32  and the error detecting code  13  to the bit string manipulating unit  111 , and obtains the special data  32  and the error detecting code  13  resulting from bit string manipulation. 
     Furthermore, the special data setting unit  113  extracts the logical block address information from the received special data setting request. The special data setting unit  113  instructs the access unit  150  to write the special data and the error detecting code  13  resulting from the bit string manipulation to the storage area  161  in the storage unit  160  associated with the extracted logical block address information. 
     The readout unit  115  receives a readout request from the host interface  130 . The readout unit  115  extracts logical block address information from the received readout request. The readout unit  115  instructs the access unit  150  to readout data stored in the storage area  161  in the storage unit  160  associated with the logical block address indicated by the extracted logical block address information and thus obtains the readout data. 
     The readout unit  115  then sends, to the first determining unit  122 , data that were stored in the user data storage area  162  as error detection target data and data that were stored in the redundant area  163  as an error detecting code associated with the error detection target data out of the readout data. If data other than the write target data  11  or the special data  32  are further contained in the data to be sent by the writing unit  114  and the special data setting unit  113  to the first generating unit  121 , the further contained data are also sent to the first determining unit  122 . For example, if a bit string indicating logical block address information contained in a write request or a special data setting request is further contained, the bit string indicating the logical block address information extracted from the readout request is further sent to the first determining unit  122 . For another example, if a predetermined bit string is further contained, the predetermined bit string is also sent to the first determining unit  122 . The readout unit  115  then obtains a first determination result sent from the first determining unit  122 . 
     If the first determination result obtained from the first determining unit  122  shows that no error is detected, the readout unit  115  sends, to the host interface  130 , a readout acknowledge containing the data that were stored in the user data storage area  162  out of the data read out from the storage area  161 . The readout acknowledge may be the entire readout data. When the error correcting code is used instead of the error detecting code, and if the obtained first determination result shows that an error correction process is possible, the readout unit  115  corrects the error of the readout data. The readout unit  115  also sends, to the host interface  130 , a readout acknowledge containing the data that were stored in the user data storage area  162  out of the error corrected data. Specifically, in response to a readout request for a logical block address that is not associated with any special data  32  and for which no error is occurred in the bit string of data stored in the storage unit  160  or an error is occurred in the bit string of data stored in the storage unit  160  but the error is in a correctable range, the readout unit  115  can send a readout acknowledge to the host device through a normally required error detection process or error correction process. 
     However, as a result of an error occurred in the bit string (resulting from the bit string manipulation) of data stored in the storage unit  160  as the special data  32 , there may be a case in which the bit string in which the error is occurred becomes identical to the bit string resulting from the bit string recovery manipulation performed by the bit string recovering unit  112  by accident, or a case in which the error in the bit string in which the error is occurred becomes in a correctable range. In such cases, a readout acknowledge similar to that in a case where the first determination result shows that no error is detected or a case where the first determination result shows that an error correction process is possible is performed even in response to the readout request for the logical block address for which the special data  32  are set. Thus, there is a possibility that a predetermined acknowledge is not returned to the host device according to the predetermined response corresponding to the special data  32 . However, such cases occur as a result of an error occurred in data stored in the storage unit  160 . The possibility that an incorrect response is returned to the host device when an error occurs in data stored in the storage unit  160  is a matter of trade-off with the cost required for a rigorous design. Therefore, the operation need not necessarily be regarded as erroneous operation. As a result, the normal readout process can be performed at a higher speed. 
     If, on the other hand, the first determination result obtained from the first determining unit  122  shows that an error is detected or that the error correction process is not possible, the readout unit  115  sends the data read out from the storage area  161 , namely, the data that were stored in the user data storage area  162  and the data that were stored in the redundant area  163  to the bit string recovering unit  112 , and obtains data resulting from the bit string recovery manipulation from the bit string recovering unit  112 . 
     The readout unit  115  then sends, to the first determining unit  122 , the data resulting from the bit string recovery manipulation that were stored in the user data storage area  162  as error detection target data and the data resulting from the bit string recovery manipulation that were stored in the redundant area  163  as an error detecting code associated with the error detection target data out of the data obtained from the bit string recovering unit  112 . If data other than the write target data or the special data  32  are further contained in the data to be sent by the writing unit  114  and the special data setting unit  113  to the first generating unit  121 , the further contained data are also sent to the first determining unit  122 . For example, if a bit string indicating logical block address information contained in a write request or a special data setting request is further contained, the bit string indicating the logical block address information extracted from the readout request is further sent to the first determining unit  122 . For another example, if a predetermined bit string is further contained, the predetermined bit string is also sent to the first determining unit  122 . The readout unit  115  then obtains a second determination result sent from the first determining unit  122 . 
     If the second determination result obtained from the first determining unit  122  shows that no error is detected, the readout unit  115  assumes predetermined bits of the special data  32  that were stored in the user data storage area  162  out of the data resulting from the bit string recovery manipulation to be the magic number  32   a  to identify the special data identification information. When the error correcting code is used instead of the error detecting code, and if the obtained second determination result shows that an error correction process is possible, the readout unit  115  corrects the error of the data resulting from the bit string recovery manipulation. The readout unit  115  then assumes predetermined bits of the data that were stored in the user data storage area  162  out of the error corrected data to be the magic number  32   a  to identify the special data identification information. The readout unit  115  further sends a predetermined acknowledge corresponding to the identified special data identification information to the host interface  130 . Specifically, in response to a readout request for a logical block address associated with special data and for which no error is occurred in the bit string of data stored in the storage unit  160  or an error is occurred in the bit string of data stored in the storage unit  160  but the error is in a correctable range as a result of the bit string recovery manipulation, the readout unit  115  can send a predetermined acknowledge to the host device. 
     However, as a result of an error occurred in the bit string (that has not been subjected to the bit string manipulation) of data stored in the storage unit  160  as normal user data, there may be a case in which the bit string of the data in which the error is occurred becomes identical to the bit string resulting from the bit string manipulation performed by the bit string manipulating unit  111  by accident, or a case in which the bit string in which the error is occurred is subjected to the bit string recovery manipulation performed by the bit string recovering unit  112  and the error in the bit string resulting from the bit string recovery manipulation becomes in a correctable range. In such cases, a predetermined response is performed even in response to the readout request for the logical block address associated with the normal user data similarly to a case where the second determination result shows that no error is detected or that an error correction process is possible. Thus, there is a possibility that a readout acknowledge which is the normal user data is not returned to the host device. However, such cases occur as a result of an error occurred in data stored in the storage unit  160 . As described above, the possibility that an incorrect response is returned to the host device when an error occurs in data stored in the storage unit  160  is a matter of trade-off with the cost required for a rigorous design. Therefore, the operation need not necessarily be regarded as erroneous operation. 
     If, on the other hand, the second determination result obtained from the first determining unit  122  shows that an error is detected or that the error correction process is not possible, the readout unit  115  sends readout state information indicating a readout error as the readout acknowledge to the host interface  130 . 
     Operations 
     Next, an example of procedures according to the first embodiment will be described in detail with reference to the drawings.  FIG. 6  illustrates an example of the writing process according to the first embodiment.  FIG. 7  illustrates an example of a special data setting process according to the first embodiment.  FIG. 8  illustrates an example of the readout process according to the first embodiment. 
     Writing Process 
     First, an example of the writing process according to the first embodiment will be described in detail with reference to  FIG. 6 . As illustrated in  FIG. 6 , in the writing process, an error detecting code is first generated in response to a write request from the host device (step S 101 ). More specifically, the host interface  130  receives a write request from the host device. The write request includes logical block address information and write target data. Upon receiving the write request from the host device, the host interface  130  sends the received write request to the writing unit  114 . Upon receiving the write request from the host interface  130 , the writing unit  114  extracts the write target data from the write request. Subsequently, the writing unit  114  sends the extracted write target data to the first generating unit  121 . The data to be sent to the first generating unit  121  may further include data other than the write target data. For example, the data may further include a bit string indicating logical block address information extracted from the write request and a predetermined bit string. Upon receiving the write target data from which an error detecting code is to be generated from the writing unit  114  that is a request source, the first generating unit  121  generates the error detecting code from the received write target data based on a predetermined method. The generated error detecting code is sent by the first generating unit  121  to the writing unit  114  that is the request source. Then, the writing unit  114  obtains the error detecting code associated with the write target data from the first generating unit  121 . Note that the error detecting code may be replaced with an error correcting code. This also applies to the description below. 
     Next, the extracted write target data and the obtained error detecting code are written to the storage area  161  in the storage unit  160  (step S 102 ), and then the writing process ends. More specifically, the writing unit  114  extracts the logical block address information from the write request. The writing unit  114  instructs the access unit  150  to write the write target data that are also extracted and the obtained error detecting code to the storage area  161  in the storage unit  160  associated with the extracted logical block address information. The access unit  150  writes the write target data and the error detecting code input from the writing unit  114  to the storage area  161  in the storage unit  160  associated with the logical block address information that is also input from the writing unit  114 . 
     Special Data Setting Process 
     Next, an example of the special data setting process according to the first embodiment will be described in detail with reference to  FIG. 7 . As illustrated in  FIG. 7 , in the special data setting process, special data  32  including a magic number are first generated in response to a special data setting request from the host device (step S 201 ). More specifically, the host interface  130  receives a special data setting request from the host device. The special data setting request includes logical block address information of a storage area to write to and special data identification information for identifying the type of a predetermined response. Upon receiving the special data setting request from the host device, the host interface  130  sends the received special data setting request to the special data setting unit  113 . Upon receiving the special data setting request from the host interface  130 , the special data setting unit  113  extracts the special data identification information from the special data setting request. Subsequently, the special data setting unit  113  generates the special data  32  including the magic number that is a bit string corresponding to the extracted special data identification information as described above referring to  FIG. 5 . 
     Next, an error detecting code is generated by using the generated special data  32  (step S 202 ). More specifically, the special data setting unit  113  sends the generated special data  32  to the first generating unit  121 . Note that the data sent to the first generating unit  121  may further include data other than the special data  32 . For example, the data may further include a bit string indicating logical block address information extracted from the special data setting request and a predetermined bit string. Upon receiving the special data  32  from the special data setting unit  113  that is a request source, the first generating unit  121  generates an error detecting code from the received special data  32  based on a predetermined method. The generated error detecting code is sent from the first generating unit  121  to the special data setting unit  113  that is the request source. As a result, the special data setting unit  113  obtains the error detecting code associated with the bit string of the generated special data  32 . Data constituted by the bit string of the special data  32  and the bit string of the error detecting code will be hereinafter referred to as manipulation target data. 
     Next, values of predetermined bits in the manipulation target data constituted by the generated special data  32  and the obtained error detecting code are manipulated (step S 203 ). More specifically, the special data setting unit  113  sends the generated special data  32  and the obtained error detecting code as the manipulation target data to the bit string manipulating unit  111 . Upon receiving the manipulation target data from the special data setting unit  113  that is the request source, the bit string manipulating unit  111  manipulates the bit string of the received manipulation target data according to a predetermined rule as described above. Then, the bit string manipulating unit  111  sends the manipulated data resulting from the bit string manipulation to the special data setting unit  113  that is the request source. As a result, the special data setting unit  113  obtains the special data  32  and the error detecting code resulting from the bit string manipulation. Note that the error detecting code may be replaced with the error correcting code as described above. 
     Next, the special data  32  and the error detecting code resulting from the bit string manipulation are written to the storage unit  160  (step S 204 ), and then the special data setting process ends. More specifically, the special data setting unit  113  extracts the logical block address information from the special data setting request. The special data setting unit  113  instructs the access unit  150  to write the special data  32  and the error detecting code resulting from the bit string manipulation to the storage area  161  in the storage unit  160  associated with the extracted logical block address information. The access unit  150  writes the special data  32  and the error detecting code resulting from the bit string manipulation input from the special data setting unit  113  to the storage area  161  in the storage unit  160  associated with the logical block address information that is also input from the special data setting unit  113 . 
     Readout Process 
     Next, an example of the readout process according to the first embodiment will be described in detail with reference to  FIG. 8 . As illustrated in  FIG. 8 , in the readout process, data are first read out from the storage unit  160  in response to a readout request from the host device (step S 301 ). More specifically, the host interface  130  receives the readout request from the host device. The readout request includes logical block address information indicating a storage location of readout target data. Upon receiving the readout request from the host device, the host interface  130  sends the received readout request to the readout unit  115 . Upon receiving the readout request from the host interface  130 , the readout unit  115  extracts the logical block address information from the readout request. The readout unit  115  then instructs the access unit  150  to readout data stored in the storage area  161  in the storage unit  160  associated with the logical block address indicated by the extracted logical block address information. The access unit  150  reads out the data stored in the storage area  161  in the storage unit  160  associated with the logical block address indicated by the logical block address information input from the readout unit  115 , and returns the readout data to the readout unit  115 . As a result, the readout unit  115  obtains the readout target data. 
     Next, an error correction process is performed on the readout data (step S 302 ). More specifically, the readout unit  115  sends, to the first determining unit  122 , data that were stored in the user data storage area  162  as error detection target data and data that were stored in the redundant area  163  as an error detecting code out of the readout data. If data other than the data that were stored in the user data storage area  162  were further contained in the data sent from the writing unit  114  and the special data setting unit  113  to the first generating unit  121 , the further contained data are also sent to the first determining unit  122  at this point. For example, if a bit string indicating logical block address information contained in a write request or a special data setting request was further contained, the bit string indicating the logical block address information extracted from the readout request is further sent to the first determining unit  122 . If a predetermined bit string was further contained, the predetermined bit string is also sent to the first determining unit  122 . Upon receiving the error detection target data and the error detecting code from the readout unit  115  that is a request source, the first determining unit  122  determines whether or not an error is present in the bit strings of the received error detection target data and error detecting code based on a predetermined method. The first determining unit  122  then sends the result of the determination (first determination result) to the readout unit  115  that is the request source. As a result, the readout unit  115  obtains the first determination result sent from the first determining unit  122 . Note that the error detecting code may be replaced with the error correcting code as described above. 
     Next, it is determined whether or not an error is detected as a result of the error determination process in step S 302  (step S 303 ). More specifically, if the first determination result obtained from the first determining unit  122  shows that no error is detected (No in step S 303 ), the process proceeds to step S 304 . If, on the other hand, the obtained first determination result shows that an error is detected (Yes in step S 303 ), the process proceeds to step S 305 . When the error correcting code is used instead of the error detecting code, the readout unit  115  proceeds to step S 304  if the first determination result shows that an error correction process is possible (No in step S 303 ), while the readout unit  115  proceeds to step S 305  if the first determination result shows that the error correction process is not possible (Yes in step S 303 ). 
     In step S 304 , the data read out in step S 301  are sent to the host device as a readout acknowledge. More specifically, the readout unit  115  sends the data that were stored in the user data storage area  162  out of the data read out in step S 301  to the host interface  130  as the readout acknowledge. When the error correcting code is used instead of the error detecting code, the readout unit  115  corrects the error in the readout data. The readout unit  115  also sends data that were stored in the user data storage area  162  out of the error corrected data as the readout acknowledge to the host interface  130 . The readout acknowledge includes the readout target data requested by the host device or readout state information. The readout state information is information indicating a readout state. The information indicating a readout state may be information indicating a readout error, for example. Upon receiving the readout acknowledge from the readout unit  115 , the host interface  130  sends the readout acknowledge to the host device and then ends the readout process. 
     In step S 305 , the bit string of data read out in step S 301  is subjected to recovery manipulation. More specifically, the readout unit  115  sends the data (the data that were stored in the user data storage area  162  and the data that were stored in the redundant area  163 ) read out in step S 301  to the bit string recovering unit  112 . Upon receiving recovery manipulation target data from the readout unit  115  that is a request source, the bit string recovering unit  112  performs the recovery manipulation of the bit string of the manipulation target data as described above. The bit string recovering unit  112  then sends data resulting from the bit string recovery manipulation to the readout unit  115  that is the request source. As a result, the readout unit  115  obtains the data resulting from the bit string recovery manipulation. Note that the error detecting code can be replaced with the error correcting code as described above. 
     Next, an error detection process is performed on the data resulting from the bit string recovery manipulation (step S 306 ). More specifically, the readout unit  115  sends, to the first determining unit  122 , the data resulting from the bit string recovery manipulation that were stored in the user data storage area  162  as error detection target data and the data resulting from the bit string recovery manipulation that were stored in the redundant area  163  as an error detecting code out of the data resulting from the bit string recovery manipulation obtained from the bit string recovering unit  112 . If data other than the data stored in the user data storage area  162  were further contained in the data sent from the writing unit  114  and the special data setting unit  113  to the first generating unit  121 , the further contained data are also sent to the first determining unit  122  at this point. For example, if a bit string indicating logical block address information contained in a write request or a special data setting request was further contained, the bit string indicating the logical block address information extracted from the readout request is further sent to the first determining unit  122 . If a predetermined bit string was further contained, the predetermined bit string is also sent to the first determining unit  122 . Upon receiving the error detection target data and the error detecting code from the readout unit  115  that is the request source, the first determining unit  122  determines whether or not an error is present in the received error detection target data and error detecting code based on a predetermined method. The first determining unit  122  then sends the result of the determination (second determination result) to the readout unit  115  that is the request source. Note that the error detecting code may be replaced with the error correcting code as described above. 
     Next, it is determined whether or not an error is detected as a result of the error determination process in step S 306  (step S 307 ). More specifically, if the second determination result obtained from the first determining unit  122  shows that no error is detected (No in step S 307 ), the process proceeds to step S 308 . If, on the other hand, the obtained second determination result shows that an error is detected (Yes in step S 307 ), the process proceeds to step S 309 . When the error correcting code is used instead of the error detecting code, the readout unit  115  proceeds to step S 308  if the second determination result shows that an error correction process is possible (No in step S 307 ), while the readout unit  115  proceeds to step S 309  if the second determination result shows that the error correction process is not possible (Yes in step S 307 ). 
     In step S 308 , a predetermined response is performed according to a magic number  32   a  in the special data  32  obtained as a result of the bit string recovery manipulation in step S 305 . More specifically, the readout unit  115  assumes predetermined bits in the data that were stored in the user data storage area  162  out of the data resulting from the bit string recovery manipulation obtained in step S 305  to be the magic number  32   a  to identify the special data identification information. When the error correcting code is used instead of the error detecting code, the readout unit  115  corrects the error in the data resulting from the bit string recovery manipulation obtained in step S 305 , and assumes predetermined bits in the data that were stored in the user data storage area  162  out of the error corrected data to be the magic number  32   a  to identify the special data identification information. Subsequently, the readout unit  115  sends a predetermined acknowledge as a readout acknowledge according to the identified special data identification information to the host interface  130 . Upon receiving the predetermined acknowledge from the readout unit  115 , the host interface  130  sends the predetermined acknowledge as the readout acknowledge to the host device and then ends the readout process. 
     In step S 309 , on the other hand, a readout error is returned to the host device. More specifically, the readout unit  115  sends readout state information indicating a readout error as the readout acknowledge to the host interface  130 . Upon receiving the readout acknowledge from the readout unit  115 , the host interface  130  sends the readout error to the host device and then ends the readout process. 
     With the above described configuration and operations, the information on logical block addresses for which special data are set need not be managed separately according to the first embodiment. This allows the used memory capacity to be reduced. Moreover, in the readout process for a logical block address for which no special data are set, if no error is detected in data stored in the storage unit  160 , a readout acknowledge can be sent to the host device only through a normally required error detection process. As a result, the normal readout process can be performed at a higher speed. 
     Furthermore, in the first embodiment, special data are associated with a certain logical block address by recording a magic number indicating that the stored data are special data in the storage area  161  in the storage medium associated with the logical block address. This eliminates the need of an additional recording medium for managing associations and the need of assigning the storage areas  161  in the storage unit  160  as storage areas for managing associations. 
     An example of a data storage device that is contrasted with the first embodiment will be described below. When a readout request for a certain logical block address is issued from a host device, the data storage device that is contrasted performs in parallel an address determination process of determining whether or not a predetermined response is set for the logical block address and a data readout process of reading out user data associated with the address from a recording medium. Then, if the result of address determination is true, the data storage device discards the user data that are read out in parallel and performs a predetermined response instead. If, on the other hand, the result of address determination is false, the data storage device returns the user data that are read out in parallel to the host. 
     Examples of the “predetermined response” to be performed by the data storage device when the special data are set can include the following patterns of functions: 
     (1) return a predetermined value in the same format as the normal response with user data; and 
     (2) return a predetermined state in a format different from that of the normal response with user data. 
     In pattern (1), if a readout request for a logical block address is issued by the host device after the data storage device is instructed to initialize data recorded at the logical block address by the host device, for example, the data storage device returns to the host device a predetermined value indicating that data are initialized in the same format as the normal response with user data. 
     In pattern (2), if a readout request for a logical block address is issued by the host device after the data storage device is instructed that reading out of data at the logical block address shall results in an error by the host device, for example, the data storage device returns to the host device a predetermined value indicating an error state in a format different from that of the normal response with user data. 
     The functions as in the patterns (1) and (2) can also be implemented by using the following technique. Information on defective areas (bad sectors) in the recording medium is recorded in a predetermined storage area in the recording medium. For processing a readout request for an address, it is determined whether or not the address is associated with a defective area based on the information stored in the predetermined storage area. If the address is associated with a defective area, a predetermined response is performed. In a process of setting so that a predetermined response is to be performed in response to a readout request for a certain logical block address by using the above configuration, information representing association between the logical block address and the predetermined response is stored in the predetermined storage area. For processing a readout request for a logical block address, information stored in a predetermined area is referred to and it is determined whether or not a predetermined response is set for the logical block address. If a predetermined response is set, the storage device can implement a function of performing the predetermined response according to the information. 
     In this manner, the functions as described above can also be implemented by separately managing logical block addresses for which it is set to perform a predetermined response in response to a readout request. However, the following disadvantages may be caused as a result of separately managing associations of special data as described above. The special data are set for each logical block address. Therefore, as the maximum value of available logical block addresses increases with the increase in the capacity of the data storage device, the amount of information to be managed is also increased. 
     Accordingly, either one of the following two approaches as described as examples below may be employed: 
     (1) set an upper limit to the number of logical block addresses for which special data can be set; or 
     (2) manage management information in a flat data structure such as a table and read out necessary information as needed from a storage medium. 
     However, there may be the following disadvantages in each of the approaches (1) and (2). According to the approach (1), the amount of management information can be reduced by setting an upper limit to the number of logical block addresses for which special data can be set. In this approach, however, the number of special data that can be set is limited. Moreover, it is practical in this approach to manage management information in a data structure such as a list. However, since a process of searching the list is needed to determine whether or not special data are set for a logical block address, it may take much time for the process as a result. 
     In the approach (2), a table for managing management information is stored in a storage medium. In response to a readout request from a host device, necessary information in the table is read out from the storage medium as needed. With such a configuration, it is possible to reduce required amount of memory. Moreover, in the approach (2), the process of searching the list is not necessary unlike the approach (1). However, it may take much time for the process of reading out from the storage medium. In addition, an area for saving the management information has to be reserved additionally in the storage medium. 
     In a data storage device such as a hard disk drive (HDD) that requires relatively much time for reading out from a storage medium, problems such as a problem that the response time for the normal response is depended on the time taken for address determination are less likely to occur by adopting the approach (1). This is because the time for the address determination process can be hidden behind the time for the data readout process by performing the address determination process and the data readout process in parallel in a data storage device in which the time for the data readout process is normally longer than the time for the address determination process such as an HDD that requires relatively much time for reading out from a storage medium. 
     However, in a data storage device such as a solid state drive (SSD) that requires relatively less time for reading out from a storage medium, the time for the address determination process cannot be hidden behind the time for the data readout process in some cases. In such case, the response time for the normal response may be longer than in a data storage device that does not have a special data setting function. 
     In the first embodiment, in contrast, the information on logical block addresses for which special data are set need not be managed separately. This allows the used memory capacity to be reduced. Moreover, in the readout process for a logical block address in which no special data are set, if no error is detected in data stored in the storage unit  160 , a readout acknowledge can be sent to the host device only through a normally required error detection process. As a result, the normal readout process can be performed at a higher speed. 
     Furthermore, in the first embodiment, special data are associated with a certain logical block address by recording a magic number indicating that the stored data are special data in the storage area  161  in the storage medium associated with the logical block address. This eliminates the need of an additional recording medium for managing associations and the need of assigning the storage areas  161  in the storage unit  160  as storage areas for managing associations. 
     Second Embodiment 
     Next, a controller, a data storage device and a program according to a second embodiment will be exemplified. In the following description, components similar to those in the first embodiment will be designated by the same reference numerals and redundant description thereof will not be repeated. 
     In the first embodiment as described above, an incorrect response may be returned to the host device in a case where, as a result of an error occurred in a bit string of data stored in the storage unit  160  as special data  32 , the bit string of the data resulting from the bit string manipulation in which the error is occurred becomes identical to the bit string resulting from the bit string recovery manipulation performed by the bit string recovering unit  112  by accident, or the bit string in which the error is occurred becomes in a correctable range, or in a case where, as a result of an error occurred in a bit string of data stored in the storage unit  160  as normal user data, the bit string of data in which the error is occurred becomes identical to the bit string resulting from the bit string manipulation performed by the bit string manipulating unit  111  by accident, or the bit string in which the error is occurred is subjected to the bit string recovery manipulation performed by the bit string recovering unit  112  and the error of the bit string resulting from the bit string recovery manipulation becomes in a correctable range, although the incorrect response need not necessarily be regarded as an erroneous operation. Therefore, the second embodiment provides an example in which two or more error detecting codes are used so as to avoid occurrence of such cases. 
     Configuration 
       FIG. 9  illustrates a schematic configuration of a data storage device  200  according to the second embodiment. As is apparent from comparison between  FIG. 9  and  FIG. 1 , the data storage device  200  ( FIG. 9 ) has a configuration similar to that of the data storage device  100  ( FIG. 1 ). In the data storage device  200 , however, the controller  110  and the host interface  130  in the data storage device  100  are replaced with a controller  210  and a host interface  230 , respectively. In addition, the data storage device  200  further includes a second generating unit  221  and a second determining unit  222 . 
     The controller  210  has a configuration similar to that of the controller  110  illustrated in  FIG. 1 , in which the special data setting unit  113 , the writing unit  114  and the readout unit  115  are replaced with a special data setting unit  213 , a writing unit  214  and a readout unit  215 , respectively. The controller  210  is interconnected with the access unit  150  and the host interface  230  via the data bus  140 , for example. 
     The host interface  230  is similar to the host interface  130  except that the host interface  230  cooperates with functional units of the writing unit  214  instead of the writing unit  114 , the special data setting unit  213  instead of the special data setting unit  113 , and the readout unit  215  instead of the readout unit  115 . Therefore, detailed description thereof will not be repeated. 
     The second generating unit  221  receives data from which an error detecting code (which will be referred to as a second error detecting code for convenience sake) is generated from a request source of the error detecting code. The second generating unit  221  generates the second error detecting code from the received data based on a predetermined method. The second generating unit  221  then sends the generated second error detecting code to the request source. Note that the error detecting code may be replaced with an error correcting code herein. If the second error detecting code is generated by the same method as the error detecting code (which will be referred to as a first error detecting code for convenience sake) generated by the first generating unit  121 , the first generating unit  121  may be used in place of the function of the second generating unit  221 . In this case, the second generating unit  221  can be omitted. 
     The second determining unit  222  receives error detection target data and a second error detecting code associated therewith from a request source of error determination. The second determining unit  222  performs an error determination process of determining whether or not an error is present in the received error detection target data and second error detecting code based on a predetermined method. The second determining unit  222  then sends the result of the error determination process to the request source. When the error detecting code is replaced with the error correcting code, the error determination process is replaced with “an error determination process of determining whether or not error correction of the received error correction target data and error correcting code is possible based on a predetermined method”. If the method of error determination performed by the second determining unit  222  is the same as that performed by the first determining unit  122 , the first determining unit  122  may be used in place of the function of the second determining unit  222 . In this case, the second determining unit  222  can be omitted. 
     The writing unit  214  receives a write request from the host interface  230 . The writing unit  214  extracts write target data from the received write request. The writing unit  214  then sends the extracted write target data to the first generating unit  121 , and obtains a first error detecting code associated with the write target data. The data to be sent to the first generating unit  121  may further include data other than the write target data. For example, the data may further include a bit string indicating logical block address information extracted from the received write request and a predetermined bit string. 
     The writing unit  214  also sends the extracted write target data and the obtained first error detecting code to the second generating unit  221 , and obtains a second error detecting code associated with the bit strings thereof. The data to be sent to the second generating unit  221  may further include data other than the write target data and the first error detecting code. For example, the data may further include a bit string indicating logical block address information extracted from the received write request and a predetermined bit string. 
     The writing unit  214  further extracts the logical block address information of a storage area to write to from the received write request. The writing unit  214  instructs the access unit  150  to write the write target data and the first and second error detecting codes to the storage area  161  in the storage unit  160  associated with the extracted logical block address information.  FIG. 10  illustrates an example of data alignment in the storage area  161  in the storage unit  160 . As illustrated in  FIG. 10 , the write target data are stored in a user data storage area  162  of a storage area  161  in the storage unit  160 . The first error detecting code is stored in a first redundant area  163   a  in a redundant area  163  of the storage area  161 , and the second error detecting code is stored in a second redundant area  163   b  in the redundant area  163 . However, the data alignment in each storage area  161  is not limited to that illustrated in  FIG. 10 . 
     The special data setting unit  213  receives a special data setting request from the host interface  230 . The special data setting unit  213  extracts special data identification information for identifying the type of a predetermined response from the special data setting request. The special data setting unit  213  also generates special data  32  (see  FIG. 4A ) including a bit string of magic number corresponding to the type of the extracted predetermined response. The method for generating the special data  32  is the same as in the special data setting unit  113  in the first embodiment. 
     The special data setting unit  213  sends the generated special data  32  to the first generating unit  121  and obtains a first error detecting code associated with the bit string of the special data  32 . The data sent to the first generating unit  121  may further include data other than the special data  32 . For example, the data may further include a bit string indicating logical block address information extracted from the received special data setting request and a predetermined bit string. 
     The special data setting unit  213  then sends the special data  32  and the first error detecting code to the bit string manipulating unit  111 , and obtains the special data  32  and the first error detecting code resulting from bit string manipulation. 
     The special data setting unit  213  further sends the special data  32  and the first error detecting code resulting from the bit string manipulation to the second generating unit  221  and obtains a second error detecting code associated with the bit strings thereof. The data to be sent to the second generating unit  221  may further include data other than the special data  32  and the first error detecting code resulting from the bit string manipulation. For example, the data may further include a bit string indicating logical block address information extracted from the received special data setting request and a predetermined bit string. 
     Furthermore, the special data setting unit  213  extracts the logical block address information from the received special data setting request. The special data setting unit  213  instructs the access unit  150  to write the special data  32  and the first error detecting code resulting from the bit string manipulation and the second error detecting code to the storage area  161  in the storage unit  160  associated with the extracted logical block address information. 
     The special data  32  resulting from the bit string manipulation are stored in the user data storage area  162  in  FIG. 10 . The first error detecting code resulting from the bit string manipulation is stored in the first redundant area  163   a  in the redundant area  163  of the storage area  161 , and the second error detecting code is stored in the second redundant area  163   b  in the redundant area  163 . However, the data alignment in each storage area  161  is not limited to that illustrated in  FIG. 10 . 
     The readout unit  215  receives a readout request from the host interface  230 . The readout unit  215  extracts logical block address information from the received readout request. The readout unit  215  instructs the access unit  150  to readout data stored in the storage area  161  in the storage unit  160  associated with the logical block address indicated by the extracted logical block address information, and obtains data read out in response thereto. 
     The alignment of the data read out by the readout unit  215  is a predetermined alignment such as the alignment illustrated in  FIG. 10 , for example. Accordingly, in the description below, data read out from the user data storage area  162  are referred to as first data, data read out from the first redundant area  163   a  are referred to as second data, and data read out from the second redundant area  163   b  are referred to as third data out of the data read out by the readout unit  215 . Note that the first data are the write target data that are not subjected to the bit string manipulation or the special data  32  resulting from the bit string manipulation. The second data are the first error detecting code that is not subjected to the bit string manipulation or the first error detecting code resulting from the bit string manipulation. The third data are the second error detecting code that is not subjected to the bit string manipulation. 
     The readout unit  215  sends, to the second determining unit  222 , the first data and the second data as error detection target data and the third data as an error detecting code associated with the error detection target data out of the readout data. If data other than the first and second data were further contained in the data sent from the writing unit  214  and the special data setting unit  213  to the second generating unit  221 , the further contained data are also sent to the second determining unit  222  at this point. For example, if a bit string indicating logical block address information contained in a write request or a special data setting request was further contained, the bit string indicating the logical block address information extracted from the readout request is further sent to the second determining unit  222 . For another example, if a predetermined bit string was further contained, the predetermined bit string is also sent to the second determining unit  222 . The readout unit  215  then obtains a third determination result sent from the second determining unit  222 . 
     If the third determination result obtained from the second determining unit  222  shows that an error is detected or that the error correction process is not possible, the readout unit  215  sends readout state information indicating a readout error as the readout acknowledge to the host interface  230 . 
     If, on the other hand, the third determination result obtained from the second determining unit  222  shows that no error is detected, the readout unit  215  sends, to the first determining unit  122 , the first data as error detection target data and the second data as the error detecting code associated with the error detection target data out of the data read out from the storage area  161 . When the error correcting code is used instead of the error detecting code generated by the second generating unit  221 , and if the third determination result shows that the error correction process is possible, the readout unit  215  corrects the error of the readout data. The error corrected data will be hereinafter referred to as first error corrected data. The readout unit  215  also sends, to the first determining unit  122 , the first data as error correction target data and the second data as an error detecting code associated with the error detection target data out of the first error corrected data. If data other than the first data were further contained in the data sent from the writing unit  214  and the special data setting unit  213  to the first generating unit  121 , the further contained data are also sent to the first determining unit  122  at this point. For example, if a bit string indicating logical block address information contained in a write request or a special data setting request was further contained, the bit string indicating the logical block address information extracted from the readout request is further sent to the first determining unit  122 . For another example, if a predetermined bit string was further contained, the predetermined bit string is also sent to the first determining unit  122 . The readout unit  215  obtains a fourth determination result sent from the first determining unit  122 . 
     If the fourth determination result obtained from the first determining unit  122  shows that no error is detected, the readout unit  215  sends a readout acknowledge containing the first data as the data requested by the host device out of the data read out from the storage area  161  to the host interface  230 . When the error correcting code is used instead of the error detecting code generated by the second generating unit  221 , and if the obtained fourth determination result shows that the error correction process is possible, the readout unit  215  sends, to the host interface  230 , a readout acknowledge containing the first data as the data requested by the host device out of the first error corrected data. This is because an error occurred in data recorded in the storage unit  160  is no longer present in the first error corrected data obtained by correcting the error. On the other hand, if the bit string has been manipulated, a result showing that the error correction process is not possible can always be obtained in the fourth determination result from the first determining unit  122 . Therefore, if a result showing that the error correction process is possible is obtained, the error correction process need not be performed. 
     However, as a result of an error occurred in the bit string of the data stored in the storage unit  160  as the special data  32 , there may be a case in which the first data (the bit string of magic number resulting from the bit string manipulation) and the second data (the first error detecting code resulting from the bit string manipulation) become identical to the bit strings resulting from the bit string recovery manipulation performed by the bit string recovering unit  112  by accident. Even in such case, the third determination result from the second determining unit  222  shows that an error is detected or that the error correction is not possible and a readout error is returned to the host device, or the third determination result shows that the error is in a correctable range and the error is corrected. Accordingly, the readout acknowledge containing the first data read out from the storage area  161  as the data will never be returned to the host interface  230 . Specifically, in response to a readout request for a logical block address that is not associated with any special data  32  and for which no error is occurred, a readout acknowledge can be sent to the host device through a normally required error detection process as described above. As a result, the normal readout process can be performed at a higher speed. 
     If, on the other hand, the fourth determination result obtained from the first determining unit  122  shows that an error is detected, the readout unit  215  sends the first data and the second data out of the data read out from the storage area  161  to the bit string recovering unit  112 , and obtains data resulting from the bit string recovery manipulation therefrom. When the error correcting code is used instead of the error detecting code, and if the fourth determination result shows that the error correction process is not possible, the readout unit  215  sends the first data and the second data out of the first error corrected data to the bit string recovering unit  112 , and obtains data resulting from the bit string recovery manipulation. 
     The readout unit  215  also sends, to the first determining unit  122 , data associated with the location of the first data out of the obtained data resulting from the bit string recovery manipulation as error detection target data and data associated with the location of the second data out of the obtained data resulting from the bit string recovery manipulation as an error detecting code associated with the error detection target data. If data other than the first data were further contained in the data sent from the writing unit  214  and the special data setting unit  213  to the first generating unit  121 , the further contained data are also sent to the first determining unit  122  at this point. For example, if a bit string indicating logical block address information contained in a write request or a special data setting request was further contained, the bit string indicating the logical block address information extracted from the readout request is further sent to the first determining unit  122 . For another example, if a predetermined bit string was further contained, the predetermined bit string is also sent to the first determining unit  122 . The readout unit  215  obtains a fifth determination result sent from the first determining unit  122 . 
     The readout unit  215  confirms that the fifth determination result obtained from the first determining unit  122  shows that no error is detected. When the error correcting code is used instead of the error detecting code generated by the first generating unit  121 , the readout unit  215  confirms that the fifth determination result shows that the error correction process is possible. 
     However, as a result of an error occurred in a bit string of the data stored in the storage unit  160  as normal user data, there may be a case in which the first data (write target data) and the second data (the first error detecting code) become identical to the bit strings resulting from the bit string manipulation performed by the bit string manipulating unit  111  by accident. Even in such case in the second embodiment, the third determination result shows that an error is detected or that the error correction is not possible and a readout error is returned to the host device, or the third determination result shows that an error is in a correctable range and the error is corrected. Accordingly, an error is never detected in the confirmation process unlike the first embodiment. In addition, even in a case where an error is occurred in a bit string of data stored in the storage unit  160  differently from the result of the bit string manipulation performed by the bit string manipulating unit  111 , the third determination result shows that an error is detected or that the error correction is not possible and a readout error is returned to the host device, or the third determination result shows that an error is in a correctable range and the error is corrected. Accordingly, an error is never detected in the confirmation process unlike the first embodiment. When the error correcting code is used instead of the error detecting code, a result showing that the error correction process is possible is confirmed as the fifth determination result, but no error is detected in the fifth determination result for the reason described above. Therefore, the error correction process subsequent to the fifth determination result can be omitted. Specifically, the process of sending predetermined data to the first determining unit  122  by the readout unit  215  so as to obtain the fifth determination result and the process of confirming the fifth determination result by the readout unit  215  may be omitted. 
     The readout unit  215  also assumes data associated with the location of the first data out of the data resulting from the bit string recovery manipulation obtained from the first determining unit  122  to be a magic number to identify the special data identification information. The readout unit  215  sends a predetermined acknowledge corresponding to the identified special data identification information to the host interface  230 . 
     Operations 
     Next, an example of procedures according to the second embodiment will be described in detail with reference to the drawings.  FIG. 11  illustrates an example of a writing process according to the second embodiment.  FIG. 12  illustrates an example of a special data setting process according to the second embodiment.  FIG. 13  illustrates an example of a readout process according to the second embodiment. 
     Writing Process 
     First, an example of the writing process according to the second embodiment will be described in detail with reference to  FIG. 11 . As illustrated in  FIG. 11 , in the writing process, a first error detecting code is first generated in response to a write request from the host device (step S 401 ). More specifically, the host interface  230  receives a write request from the host device. The write request includes logical block address information and write target data. Upon receiving the write request from the host device, the host interface  230  sends the received write request to the writing unit  214 . Upon receiving the write request from the host interface  230 , the writing unit  214  extracts the write target data from the received write request. Subsequently, the writing unit  214  sends the extracted write target data to the first generating unit  121 . The data to be sent to the first generating unit  121  may further include data other than the write target data. For example, the data may further include a bit string indicating logical block address information extracted from the write request and a predetermined bit string. Upon receiving the write target data from which the first error detecting code is to be generated from the writing unit  214  that is a request source, the first generating unit  121  generates the error detecting code from the received write target data based on a predetermined method. The generated first error detecting code is sent by the first generating unit  121  to the writing unit  214  that is the request source. Then, the writing unit  214  obtains the first error detecting code associated with the write target data from the first generating unit  121 . Note that the error detecting code may be replaced with the error correcting code in the description including the description below. 
     Next, a second error detecting code is generated (step S 402 ). More specifically, the writing unit  214  sends the extracted write target data and the obtained first error detecting code to the second generating unit  221 . The data to be sent to the second generating unit  221  may further include data other than the write target data and the first error detecting code. For example, the data may further include a bit string indicating logical block address information extracted from the write request and a predetermined bit string. Upon receiving the write target data and the first error detecting code from which the second error detecting code is to be generated from the writing unit  214  that is a request source, the second generating unit  221  generates the second error detecting code from the bit strings thereof based on a predetermined method. The generated second error detecting code is sent by the second generating unit  221  to the writing unit  214  that is the request source. Then, the writing unit  214  obtains the second error detecting code associated with the write target data and the first error detecting code from the second generating unit  221 . If the second error detecting code is generated by the same method as the first error detecting code, the second error detecting code may be generated by using the first generating unit  121  in place of the second generating unit  221 . In this case, the second generating unit  221  can be omitted. 
     Next, the extracted write target data and the obtained first and second error detecting codes are written to the storage area  161  in the storage unit  160  (step S 403 ), and then the writing process ends. More specifically, the writing unit  214  extracts the logical block address from the write request. The writing unit  214  instructs the access unit  150  to write the write target data that are also extracted and the obtained first and second error detecting codes to the storage area  161  in the storage unit  160  associated with the extracted logical block address information. The access unit  150  writes the write target data and the first and second error detecting codes input from the writing unit  214  to the storage area  161  in the storage unit  160  associated with the logical block address information that is also input from the writing unit  214 . As described with reference to  FIG. 10 , the write target data are stored in the user data storage area  162  in the storage area  161 . The first error detecting code is stored in the first redundant area  163   a  in the redundant area  163  of the storage area  161 , and the second error detecting code is stored in the second redundant area  163   b  in the redundant area  163 . However, the storage areas are not limited thereto. 
     Special Data Setting Process 
     Next, an example of the special data setting process according to the second embodiment will be described in detail with reference to  FIG. 12 . As illustrated in  FIG. 12 , in the special data setting process, special data  32  including a magic number are first generated in response to a special data setting request from the host device (step S 501 ). More specifically, the host interface  230  receives a special data setting request. The special data setting request includes logical block address information of a storage area to write to and special data identification information for identifying the type of a predetermined response. Upon receiving the special data setting request from the host device, the host interface  230  sends the received special data setting request to the special data setting unit  213 . Upon receiving the special data setting request from the host interface  230 , the special data setting unit  213  extracts the special data identification information from the special data setting request. Subsequently, the special data setting unit  213  generates the special data  32  including the magic number that is a bit string corresponding to the extracted special data identification information. The method for generating the special data  32  is the same as in the special data setting unit  113 . 
     Next, a first error detecting code is generated by using the generated special data  32  (step S 502 ). More specifically, the special data setting unit  213  sends the generated special data  32  to the first generating unit  121 . Note that the data sent to the first generating unit  121  may further include data other than the special data  32 . For example, the data may further include a bit string indicating logical block address information extracted from the special data setting request and a predetermined bit string. Upon receiving the special data  32  from the special data setting unit  213  that is the request source, the first generating unit  121  generates the first error detecting code from the received special data  32  based on a predetermined method. The generated first error detecting code is sent from the first generating unit  121  to the special data setting unit  213  that is the request source. As a result, the special data setting unit  213  obtains the first error detecting code associated with the bit string of the generated special data  32 . 
     Next, values of predetermined bits in the manipulation target data constituted by the generated special data  32  and the obtained first error detecting code are manipulated (step S 503 ). More specifically, the special data setting unit  213  sends the generated special data  32  and the obtained first error detecting code as the manipulation target data to the bit string manipulating unit  111 . Upon receiving the manipulation target data from the special data setting unit  213  that is the request source, the bit string manipulating unit  111  manipulates the bit string of the received manipulation target data according to a predetermined rule as described above. Then, the bit string manipulating unit  111  sends the manipulation target data resulting from the bit string manipulation to the special data setting unit  213  that is the request source. As a result, the special data setting unit  213  obtains the special data  32  and the first error detecting code resulting from the bit string manipulation. Note that the error detecting code may be replaced with the error correcting code as described above. 
     Next, a second error detecting code is generated from the special data  32  and the first error detecting code resulting from the bit string manipulation (step S 504 ). More specifically, the special data setting unit  213  sends the special data  32  and the first error detecting code resulting from the bit string manipulation to the second generating unit  221 . The data to be sent to the second generating unit  221  may further include data other than the obtained special data  32  and first error detecting code resulting from the bit string manipulation. For example, the data may further include a bit string indicating logical block address information extracted from the special data setting request and a predetermined bit string. Upon receiving the special data  32  and the first error detecting code resulting from the bit string manipulation from the special data setting unit  213  that is the request source, the second generating unit  221  generates the second error detecting code from the received special data  32  and first error detecting code based on a predetermined method. The generated second error detecting code is sent from the second generating unit  221  to the special data setting unit  213  that is the request source. As a result, the special data setting unit  213  obtains the second error detecting code associated with the special data  32  and the first error detecting code resulting from the bit string manipulation. If the second error detecting code is generated by the same method as the first error detecting code, the first generating unit  121  may be used in place of the function of the second generating unit  221 . 
     Next, the special data  32  and the first error detecting code resulting from the bit string manipulation and the obtained second error detecting code are written to the storage area  161  in the storage unit  160  (step S 505 ), and then the writing process ends. More specifically, the special data setting unit  213  extracts the logical block address information from the special data setting request. The special data setting unit  213  instructs the access unit  150  to write the special data  32  and the first error detecting code resulting from the bit string manipulation and the obtained second error detecting code to the storage area  161  in the storage unit  160  associated with the extracted logical block address information. The access unit  150  writes the special data  32  and the first error detecting code resulting from the bit string manipulation and the obtained second error detecting code to the storage area  161  in the storage unit  160  associated with the extracted logical block address information. The special data  32  resulting from the bit string manipulation are stored in the user data storage area  162 . In addition, as illustrated in  FIG. 10 , the first error detecting code resulting from the bit string manipulation is stored in the first redundant area  163   a  in the redundant area  163 , and the second error detecting code is stored in the second redundant area  163   b  in the redundant area  163 . However, the storage areas are not limited thereto. 
     Readout Process 
     Next, an example of the readout process according to the second embodiment will be described in detail with reference to  FIG. 13 . As illustrated in  FIG. 13 , in the readout process, data are first read out from the storage unit  160  in response to a readout request from the host device (step S 601 ). More specifically, the host interface  230  receives the readout request from the host device. The readout request includes logical block address information indicating a storage location of readout target data. Upon receiving the readout request from the host device, the host interface  230  sends the received readout request to the readout unit  215 . Upon receiving the readout request from the host interface  230 , the readout unit  215  extracts the logical block address information from the received readout request. The readout unit  215  then instructs the access unit  150  to readout data stored in the storage area  161  in the storage unit  160  associated with the logical block address indicated by the extracted logical block address information. The access unit  150  reads out the data stored in the storage area  161  in the storage unit  160  associated with the logical block address indicated by the logical block address information input from the readout unit  215 , and returns the readout data to the readout unit  215 . As a result, the readout unit  215  obtains the readout target data. 
     Next, an error detection process using the second error detecting code is performed on the readout data (step S 602 ). More specifically, the readout unit  215  sends, to the second determining unit  222 , the first data and the second data as error detection target data and the third data as the second error detecting code out of the readout data. If data other than the first and second data were further contained in the data sent from the writing unit  214  and the special data setting unit  213  to the second generating unit  221 , the further contained data are also sent to the second determining unit  222  at this point. For example, if a bit string indicating logical block address information contained in a write request or a special data setting request was further contained, the bit string indicating the logical block address information extracted from the readout request is further sent to the second determining unit  222 . For another example, if a predetermined bit string was further contained, the predetermined bit string is also sent to the second determining unit  222 . Upon receiving the first and second data from the readout unit  215  that is the request source, the second determining unit  222  determines whether or not an error is present in the received first and second data based on a predetermined method. The second determining unit  222  then sends the result of the determination (third determination result) to the readout unit  215  that is the request source. As a result, the readout unit  215  obtains the third determination result sent from the second determining unit  222 . Note that the error detecting code may be replaced with the error correcting code as described above. 
     Next, it is determined whether or not an error is detected as a result of the error determination process in step S 602  (step S 603 ). More specifically, if the third determination result obtained from the second determining unit  222  shows that an error is detected (Yes in step S 603 ), the process proceeds to step S 604 . If, on the other hand, the obtained third determination result shows that no error is detected (No in step S 603 ), the process proceeds to step S 605 . When the error correcting code is used instead of the error detecting code, the readout unit  215  proceeds to step S 604  if the third determination result shows that the error correction process is not possible (Yes in step S 603 ), while the readout unit  215  proceeds to step S 605  if the third determination result shows that the error correction process is possible (Yes in step S 603 ). 
     In step S 604 , a readout error is sent in response to the readout request from the host device. More specifically, the readout unit  215  sends readout state information indicating a readout error as the readout acknowledge to the host interface  230 . Upon receiving the readout acknowledge from the readout unit  215 , the host interface  230  sends the readout error to the host device and then ends the readout process. 
     In step S 605 , an error detection process using the first error detecting code that is the second data is performed on the first data and the second data out of the readout data. More specifically, the readout unit  215  sends, to the first determining unit  122 , the first data as error detection target data and the second data as the first error detecting code out of the readout data. When the error correcting code is used instead of the error detecting code generated by the second generating unit  221 , the readout unit  215  corrects the error in the first and second data. The error corrected first and second data will be hereinafter referred to as first error corrected data. The readout unit  215  also sends, to the first determining unit  122 , the first data as the error correction target data and the second data as the first error detecting code out of the first error corrected data. If data other than the first data were further contained in the data sent from the writing unit  214  and the special data setting unit  213  to the first generating unit  121 , the further contained data are also sent to the first determining unit  122  at this point. For example, if a bit string indicating logical block address information contained in a write request or a special data setting request was further contained, the bit string indicating the logical block address information extracted from the readout request is further sent to the first determining unit  122 . For another example, if a predetermined bit string was further contained, the predetermined bit string is also sent to the first determining unit  122 . Upon receiving the error detection target data and the first error detecting code from the readout unit  215  that is the request source, the first determining unit  122  determines whether or not an error is present in the received error detection target data and first error detecting code based on a predetermined method. The first determining unit  122  then sends the result of the determination (fourth determination result) to the readout unit  215  that is the request source. Note that the error detecting code may be replaced with the error correcting code as described above. 
     Next, it is determined whether or not an error is detected as a result of the error determination process in step S 605  (step S 606 ). More specifically, if the fourth determination result obtained from the first determining unit  122  shows that no error is detected (No in step S 606 ), the process proceeds to step S 607 . If, on the other hand, the obtained fourth determination result shows that an error is detected (Yes in step S 606 ), the process proceeds to step S 608 . When the error correcting code is used instead of the error detecting code, the readout unit  215  proceeds to step S 607  if the fourth determination result shows that the error correction process is possible (No in step S 606 ), while the readout unit  215  proceeds to step S 608  if the fourth determination result shows that the error correction process is not possible (Yes in step S 606 ). 
     In step S 607 , the data read out in step S 601  are sent to the host device as a readout acknowledge. More specifically, the readout unit  215  sends the first data as the readout acknowledge out of the data read out in step S 601  to the host interface  230 . When the error correcting code is used instead of the error detecting code generated by the second generating unit  221 , the readout unit  215  corrects the error in the readout data to obtain the first error corrected data as described above. Accordingly, the readout unit  215  sends the first data out of the first error corrected data as the readout acknowledge to the host interface  230 . Upon receiving the readout acknowledge from the readout unit  215 , the host interface  230  sends the readout acknowledge to the host device and then ends the readout process. 
     In step S 608 , the bit string of data read out in step S 601  is subjected to recovery manipulation. More specifically, if the fourth determination result obtained in step S 605  shows that an error is detected, the readout unit  215  sends the first and second data out of the data read out in step S 601  to the bit string recovering unit  112 . When the error correcting code is used instead of the error detecting code generated by the second generating unit  221 , the readout unit  215  sends the first and second data out of the first error corrected data to the bit string recovering unit  112  if the fourth determination result shows that the error correction process is not possible. Upon receiving the first and second data that are recovery manipulation target from the readout unit  215  that is the request source, the bit string recovering unit  112  performs the recovery manipulation of the bit string of the data as described above. The bit string recovering unit  112  then sends data resulting from the bit string recovery manipulation to the readout unit  215  that is the request source. As a result, the readout unit  215  obtains the data resulting from the bit string recovery manipulation. Note that the error detecting code can be replaced with the error correcting code as described above. 
     Next, an error detection process using the first error detecting code is performed on the data resulting from the bit string recovery manipulation (step S 609 ). More specifically, the readout unit  215  sends, to the first determining unit  122 , data associated with the location of the first data as error detection target data and data associated with the location of the second data as the first error detecting code out of the data resulting from the bit string recovery manipulation obtained from the bit string recovering unit  112 . If data other than the first data were further contained in the data sent from the writing unit  214  and the special data setting unit  213  to the first generating unit  121 , the further contained data are also sent to the first determining unit  122  at this point. For example, if a bit string indicating logical block address information contained in a write request or a special data setting request was further contained, the bit string indicating the logical block address information extracted from the readout request is further sent to the first determining unit  122 . For another example, if a predetermined bit string was further contained, the predetermined bit string is also sent to the first determining unit  122 . Upon receiving the error detection target data and the first error detecting code from the readout unit  215  that is the request source, the first determining unit  122  determines whether or not an error is present in the received error detection target data and first error detecting code based on a predetermined method. The first determining unit  122  then sends the result of the determination (fifth determination result) to the readout unit  215  that is the request source. Note that the error detecting code may be replaced with the error correcting code as described above. 
     Next, it is confirmed that no error is detected in the fifth determination result obtained in step S 609  (step S 610 ). More specifically, the readout unit  215  confirms that the fifth determination result obtained from the first determining unit  122  shows that no error is detected. When the error correcting code is used instead of the error detecting code generated by the first generating unit  121 , the readout unit  215  confirms that the fifth determination result shows that the error correction process is possible. Moreover, the process of sending data to the first determining unit  122  by the readout unit  215  so as to obtain the fifth determination result (step S 609 ) and the process of confirming the fifth determination result by the readout unit  215  (step S 610 ) may be omitted. 
     Next, a predetermined response is performed according to a magic number  32   a  in the special data  32  obtained as a result of the bit string recovery manipulation in step S 608  (step S 611 ). More specifically, the readout unit  215  assumes the bit string of data associated with the location of the first data out of the data resulting from the bit string recovery manipulation obtained in step S 608  to be the magic number  32   a  to identify the special data identification information. Subsequently, the readout unit  215  sends a predetermined acknowledge as a readout acknowledge according to the identified special data identification information to the host interface  230 . Upon receiving the readout acknowledge from the readout unit  215 , the host interface  230  sends the predetermined acknowledge as the readout acknowledge to the host device, and then ends the readout process. 
     With the configuration and operations as described above, the second error detecting code is given to the special data and the first error detecting code in the second embodiment. Thus, it is possible to prevent the possibility that an incorrect response is returned to the host device in a case where, as a result of an error occurred in the bit string of data stored in the storage unit  160  as special data  32 , the bit string resulting from the bit string manipulation in which the error is occurred becomes identical to the bit string resulting from the bit string recovery manipulation performed by the bit string recovering unit  112  by accident, or the bit string in which the error is occurred becomes in a correctable range, or in a case where, as a result of an error occurred in a bit string of data stored in the storage unit  160  as normal user data, the bit string of data in which the error is occurred becomes identical to the bit string resulting from the bit string manipulation performed by the bit string manipulating unit  111  by accident, or the bit string in which the error is occurred is subjected to the bit string recovery manipulation performed by the bit string recovering unit  112  and the error of the bit string resulting from the bit string recovery manipulation becomes in a correctable range, although the incorrect response need not necessarily be regarded as an erroneous operation. Since the other components, operations and effects are similar to those in the first embodiment, detailed description thereof is not repeated here. 
     The operations in the embodiment described above may be implemented by software or hardware. When the operations are implemented by software, the controller, the data storage device and the program are implemented by reading out and executing a predetermined program by an information processing device such as a CPU, for example. The predetermined program may be recorded on a recording medium such as a CD-ROM, a DVD-ROM or a flash memory, or may be recorded on a storage device connected to a network. The information processing device reads out or downloads and executes the predetermined program. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirits of the inventions.