Patent Publication Number: US-2011059628-A1

Title: Secure digital card with two micro-sd cards in striping data access

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The present invention relates to secure digital (SD) card. More particularly, the present invention relates to a SD card by a SD card adaptor with two micro-SD cards in striping data access through an invented controller. 
     2. Description of Related Art 
     A flash memory storage card is a portable storage medium, quite popularly used in digital still-image cameras, digital video cameras, mobile phones, or various portable electronic apparatuses. Flash memory storage card has a number of advantages over hard disks, such as being smaller, lighter, portable, silent, power-saving and faster to boot-up. 
     SD is an acronym for Secure Digital (SD) having 3 kinds of formats: SD, mini-SD, micro-SD. Micro-SD is the smallest memory card available commercially. SD is commonly used in digital still-image cameras, digital video cameras, and portable media players. Micro-SD is commonly used in cellular phones, handheld GPS devices, and expandable USB flash memory drives. In year 2008, it is estimated that micro-SD and SD cards occupy around 80% share of total flash card market. The price of micro-SD cards is down to almost the same price of SD cards of the same capacity. 
     How to make use the micro-SD more efficiently to achieve the better performance is at least concerned in the present invention. 
     SUMMARY OF THE INVENTION 
     The invention provides a SD card composed of two micro-SD cards, so that the storage capacity and the operation speed can be improved. 
     The invention provides a secure digital (SD) card adaptor, comprising a plurality of I/O pads, for communicating with an external device. Further, a first adapting structure is included for plugging in a first micro-SD card. A second adapting structure is included for plugging in a second micro-SD card. A controller is included for adapting the first adapting structure and the second adapting structure for data access by the external device via the I/O pads. Wherein, the controller configures a total storing space into a plurality of storage sections for alternatively mapping to the first adapting structure and the second adapting structure. 
     The invention also provides a secure digital (SD) card, including a containing case, a plurality of I/O pads, a first micro-SD card, a second micro-SD card, and a controller. The I/O pads is for communicating with an external device. The first micro-SD card has a plurality of first storage sections, being embedded or plugged into the containing case. The second micro-SD card has a plurality of second storage sections, being embedded or plugged into the containing case. The controller controls the first micro-SD card and the second micro-SD card to be accessed from the external device via the I/O pads. The controller configures the first storage sections and the second storage sections alternatively into a total storage space. 
     The invention also provides a method for constructing a secure digital (SD) card with dual micro-SD cards. The method includes providing a SD card adaptor, comprising a first adapting structure, a second adapting structure, and a controller. A first micro-SD card is plugged into the first adapting structure. A second micro-SD card is plugged into the second adapting structure. The controller serves as a bridge in a striping manner for the first micro-SD card and the second micro-SD card to communicate with an external device in data accessing. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
         FIG. 1  is a drawing, schematically illustrating a structure of a SD card with dual micro-SD cards, according to an embodiment of the present invention. 
         FIG. 2  is a drawing, schematically illustrating the controller in  FIG. 1 , according to an embodiment of the present invention. 
         FIG. 3  is a drawing, schematically the dimension and mechanical structure of the SD card with dual micro-SD cards, according to an embodiment of the present invention. 
         FIG. 4  is a drawing, schematically illustrating the data structure in mapping to the two micro-SD cards, according to an embodiment of the present invention. 
         FIG. 5  is a drawing, schematically the mechanical assembly structure of the SD card with dual micro-SD cards, according to an embodiment of the present invention. 
         FIG. 6  is a drawing, schematically illustrating the electronic circuit layout of the SD card with dual micro-SD cards, according to an embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention bridges two micro-SD cards into a SD card based on a striping mode that performs both capacity aggregation and speed aggregation. Several embodiments are provided for descriptions of the invention but not limit the invention. In addition, the embodiments can be further properly combined into another embodiment. 
     For an aspect of the invention, the present invention constructs a SD Flash card with two micro-SD cards by a dual micro-SD to SD adaptor. There are 3 kinds of SD memory cards which are classified by storage capacity: (1) Standard Capacity SD Memory Card (SDSC) which is up to and including 2 GB, (2) High Capacity SD Memory Card (SDHC) which is more than 2 GB and up to and including  3 2 GB, (3) Extended Capacity SD Memory Card (SDXC) which is more than 32 GB and up to and including 2 TB. SD1.0 defines DS (Default Speed) card type up to 25 MHz (12.5 MB/s) 3.3V signaling. SD2.0 defines HS (High Speed) card type up to 50 MHz (25 MB/s) 3.3V signaling. SD3.0 defines 2 new UHS-I (Ultra High Speed Phase I) card types: UHS50 (up to SDR50/DDR50, 100 Mhz 50 MB/s 1.8V signaling) and UHS104 (up to SDR104, 208 Mhz 1.8V signaling). UHS-I is not applied to SDSC card but can be applied to SDHC and SDXC card. The present invention proposes a controller that can be installed on the proposed adaptor of the same form factor as SD to bridge two micro-SD cards of speed type either DS, HS, UHS50 or UHS104 to UHS104. However, the present invention is not limited to these types of SD interface speeds. The controller performs striping access function to achieve almost double throughput performance in sequential read/write for the target SD interface speed. The first example is that two 2 GB micro-SDSC (DS type) cards of 10 MB/s sequential read/write throughput can be bridged to a 4 GB SDHC (HS type) card of 20 MB/s sequential read/write throughput. The second example is that two 8 GB micro-SDHC (HS type) cards of 20 MB/s sequential read and 15 MB/s sequential write throughput can be bridged to either a 16 GB SDHC (UHS104 type) card of 40 MB/s sequential read and 30 MB/s sequential write throughput. The third example is that two 32 GB micro-SDHC (UHS104 type) cards of 60 MB/s sequential read and 35 MB/s sequential write throughput can be bridged to a 64 GB SDXC (UHS104 type) card of 90 MB/s sequential read and 70 MB/s sequential write throughput. 
       FIG. 1  is a drawing, schematically illustrating a structure of a SD card with dual micro-SD cards, according to an embodiment of the present invention. In  FIG. 1 , the SD card  100  includes a controller  110 , a first micro-SD card  120  and a second micro-SD card  130 . The form factor of the SD card  100  in the present invention is same as a normal SD card. However, the storage capacity of the SD card  100  is the sum of the micro-SD cards  120  and  130 . The controller  110  is serving as a bridge which combines the two micro-SD cards  120  and  130  as if they are one single memory SD card. In other words, the SD card adaptor can be plugged in with the two micro-SD cards  120  and  130 . Here in the example, the two micro-SD cards  120  and  130  are plugged into the adaptor. However, the micro-SD cards  120  and  130  can also be directly embedded in the adaptor without changing the operation mechanism as described in the following description. The controller  110  implemented on the adaptor can combine the two micro-SD cards  120  and  130  into a single memory space. The controller  110  configures storage sections of the first and second micro-SD cards  120  and  130 . 
       FIG. 2  is a drawing, schematically illustrating the controller in  FIG. 1 , according to an embodiment of the present invention. In  FIG. 2 , the controller  110  includes a first control unit  111 , such as SD device interface controller, a second control unit  112 , such as micro SD device interface controller, a third control unit  113 , such as another micro SD device interface controller. In addition, a striping engine  114  and a buffer unit  115 , such as striping data buffer are included in the controller  110 . The first control unit  111  serves as an interface between an external device, such as a host of digital camera et al. (not shown in the drawing) and the two micro-SD cards  120  and  130  for communication. The second controller  112  is in association with the first control unit  111  for accessing the first micro-SD card  120 . The third controller  113  is in association with the first control unit  111  for accessing the second micro-SD card  130 . The buffer unit  115  is for buffering data being accessed by the external device. The striping engine  114  is for mapping the total storage space with the first storage sections and the second storage sections. In other words, the controller  110  can bridge the two micro-SD cards  120  and  130  into a single SD card  100 , which is recognized as a single SD card by the external device. 
       FIG. 3  is a drawing, schematically the dimension and mechanical structure of the SD card with dual micro-SD cards, according to an embodiment of the present invention. In  FIG. 3 , the case of the SD card  100  can be in the dimension as a standard size of a SD card, formed by two covers. For example in  FIG. 3(   a ), the SD card carries the two micro-SD cards  202  and  204 . The cover in  FIG. 3(   b ) exposes the I/O terminals  200  according the usual specification of the SD card. 
     Alternatively, before the micro-SD cards are plugged in, the SD case is like a SD card adaptor, including a plurality of I/O pads, for communicating with an external device. In addition, a first adapting structure is included for plugging an external first micro-SD card. A second adapting structure is included for plugging an external second micro-SD card. A controller is included for connecting the first adapting structure and the second adapting structure so as to a data accesses from the external device by the I/O pads. Wherein, the controller configures a total storing space into a plurality of storage sections for alternatively mapping to the first adapting structure and the second adapting structure. 
     In considering the dimension of the dual microSD to SD adaptor and the micro-SD card, because the SD dimension is 32 mm×24 mm×2.1 mm and the micro-SD dimension is 15 mm×11 mm×1.0 mm, it is feasible for a SD adaptor to contain two micro-SD cards and a striping controller. 
     Two 8 GB microSDHC (HS mode) cards of 20 MB/s sequential read and 15 MB/s sequential write throughput can be bridged to a 16 GB SDHC (HS mode) card of 20 MB/s sequential read/write throughput. By jump option of, for example, “UHS104 mode”, the two 8 GB microSD cards can be bridged to a 16 GB SDHC (UHS104 mode) card of 40 MB/s sequential read and 30 MB/s sequential write throughput. 
     By the SD3.0 standard specification, UHS-I mode can be applied to SDHC card. The present invention can upgrade the two microSDHC cards of HS mode to a SDHC card of UHS104 mode to get double performance, compared with the normal single micro-SD to SD adaptor. 
     From the data structure, the storage space can be configured to alternatively distribute to the two micro-SD card.  FIG. 4  is a drawing, schematically illustrating the data structure in mapping to the two micro-SD cards, according to an embodiment of the present invention. 
     In  FIG. 4 , the total storage space  300 , recognized by the external device, can be provided in the SD card with dual micro-SD cards. The storage space  300  can be configured into a plurality of storage sections in A 1 , B 1 , A 2 , B 2 , A 3 , B 3 , . . . etc. The micro-SD card  202  is also configured into storage sections in A 1 , A 2 , A 3 , . . . , etc. The micro-SD card  204  is also configured into storage sections in B 1 , B 2 , B 3 , . . . , etc. As a result, the storage sections in the storage space  300 , recognized by the external device, are alternatively mapped to micro-SD card  202  and micro-SD card  204 . 
     Further in example, the buffer unit  115  can be used to respectively buffer the data to be written to the micro-SD cards  202  and  204 . This also indicated that the two micro-SD cards  202  and  204  can be written in a parallel manner. 
       FIG. 5  is a drawing, schematically the mechanical assembly structure of the SD card with dual micro-SD cards, according to an embodiment of the present invention. In  FIG. 5 , the mechanical assembly structure of the SD card  100  includes a secure digital (SD) card adaptor and two micro-SD cards  202  and  204 . The SD card adaptor has a plurality of I/O pads  200 , shown in  FIGS. 3 and 6 , for communicating with an external device. The SD card adaptor includes a first adapting structure  206  for plugging a micro-SD card  202 . The SD card adaptor also includes a second adapting structure  208  for plugging another micro-SD card  204 . After the two micro-SD cards  202 ,  204  are plugged into the adapting structures  206 ,  208 , the SD card with dual micro-SD cards is formed and treated as a single SD card in actual use. The adapting structures  206 ,  208  include the insert holes for containing the micro-SD card and the interconnect structure for connection to the controller. The SD card adaptor  100  can also have no the adapting structures  206  and  208  in the case of that the two micro-SD cards  202  and  204  are installed in a non-removable manner into the case of SD card adaptor. 
       FIG. 6  is a drawing, schematically the electronic circuit layout of the SD card with dual micro-SD cards, according to an embodiment of the present invention. In  FIG. 6 , after plugging the two micro-SD cards,  202 ,  204 , they are fixed in the inner space. The SD-card adaptor also has the I/O pads  200  for connecting with the external device for data communication. A controller  110  is implemented in the SD-card adaptor for connecting the first adapting structure  206  and the second adapting structure  208  so as to have a data accesses from the external device by the I/O pads  200 . The controller  110  configures a total storing space into a plurality of storage sections for alternatively mapping to the first adapting structure  204  and the second adapting structure  208  when the micro-SD cards are plugged in. 
     From the aspect in construction the SD card with dual micro-SD cards, the invention for example provides a method for constructing a secure digital (SD) card with dual micro-SD cards. The method includes providing a SD card adaptor, comprising a first adapting structure, a second adapting structure, and a controller. A first micro-SD card is plugged into the first adapting structure. A second micro-SD card is plugged into the second adapting structure. The controller serves as a bridge for the two micro-SD card and the second micro-SD card to communicate with an external device in data accessing. 
     For the more embodiments in various modifications for better detail, The SD card adaptor is configured based on striping manner. The size of each of the storage sections is a chunk size determined by the striping engine. 
     Further, if just one micro-SD card is in use, the operation still remains as shown in  FIG. 4  but ignore the space in A 1 , A 2 , A 3 . . . , etc., or B 1 , B 2 , B 3  . . . etc. This is just a choice without changing the configuration of the present invention. 
     For the further embodiments, for example, the controller can automatically recognize the plugged two micro-SD cards and achieving an operation speed for accessing the two micro-storage cards. The two micro-SD cards may have the same operation speed or different operations speeds. 
     For the further embodiments, for example, the first micro-SD card and the second micro-SD card have a same storage capacity or different storage capacities. 
     For the further embodiments, for example, the first micro-SD card and the second micro-SD card are in a same spec-type or different spec-types. 
     For the further embodiments, for example, each of the micro-SD cards has a SD interface speed type, such as DS, HS, UHS50 or UHS104. 
     For the further embodiments, for example, the first micro-SD card and the second micro-SD card are operated at the same SD interface speed. 
     For the further embodiments, for example, the first micro-SD card and the second micro-SD card are operated at different SD interface speeds. 
     For the further embodiments, for example, the first micro-SD card and the second micro-SD card are parallel in internal access operation. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing descriptions, it is intended that the present invention covers modifications and variations of this invention if they fall within the scope of the following claims and their equivalents.