Abstract:
A system, apparatus and method are provided for discerning a host interface, the system including a host having at least one interface, a device in signal communication with the at least one interfaces an interface identifier for identifying a specification of the at least one interface, the interface identifier having at least one electrical characteristic sensor in signal communication with the at least one interface, at least two switches coupled to the at least one interface, each switch in signal communication with a corresponding pull resistor coupled to a pull voltage, and a selectable device interface in signal communication with the host for communicating with the host in response to the electrical characteristic sensor the apparatus including an interface identifier having at least two switches coupled to an interface, each switch in signal communication with a corresponding pull resistor coupled to a pull voltage; and the method including connecting at least one pull resistor to the interface, sequentially applying at least one pull voltage to the at least one pull resistor, measuring at least one loaded electrical characteristic of the interface while the sequentially applied at least one pull voltage is applied to the at least one pull resistor, comparing the at least one loaded electrical characteristic with at least one predetermined value, and identifying a specification of the interface in accordance with the comparison.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present disclosure relates to device to host interfaces, and more particularly relates to device interfaces with host-type recognition. Devices such as smart cards, Subscriber Identification Module (SIM) cards, and flash cards first connect to a host and then operate in accordance with an application. The types of hosts to which the devices can be connected continue to increase. For example, a card device may be alternately connected to a mobile phone an MP3 player, a Portable Media Player (PMP), and the like. 
         [0002]    As shown in  FIG. 1  a conventional interface system  10  includes a host  12  and a device  16 . The host  12  includes a host interface  14 . The device  16  includes a fixed device interface  18 , and a controller  20  connected to the device interface. In operation the device  16  is connected to the host  12 . The host  12  and the device  16  communicate with each other via the host interface  14  and the fixed device interface  18 . The host interface  14  and the fixed device interface  18  have to have the same interface specification. 
         [0003]    It is desirable to connect the device to an increasing variety of types of hosts and still enable to device to operate in accordance with an application. Unfortunately, since the typical host does not support all types of interfaces, the host can only communicate with the specific devices that use the same type of interface as the host. Devices such as smart cards, SIM cards and flash cards can be designed to support a plurality of interfaces. However, if the device cannot match its interface to the host interface, the device cannot communicate with a host having a fixed interface of a different type. The present disclosure addresses these and other issues. 
       SUMMARY OF THE INVENTION 
       [0004]    These and other drawbacks and disadvantages of the prior art are addressed by an apparatus and method for discerning a host interface. 
         [0005]    An exemplary system for discerning a host interface includes a host having at least one interface, a device in signal communication with the at least one interface, an interface identifier for identifying a specification of the at least one interface, the interface identifier having at least one electrical characteristic sensor in signal communication with the at least one interface, at least two switches coupled to the at least one interface, each switch in signal communication with a corresponding pull resistor coupled to a pull voltage, and a selectable device interface in signal communication with the host for communicating with the host in response to the electrical characteristic sensor. 
         [0006]    An exemplary apparatus for discerning a host interface includes an interface identifier having at least two switches coupled to an interface, each switch in signal communication with a corresponding pull resistor coupled to a pull voltage. 
         [0007]    An exemplary method for discerning a host interface includes connecting at least one pull resistor to the interface, sequentially applying at least one pull voltage to the at least one pull resistor measuring at least one loaded electrical characteristic of the interface while the sequentially applied at least one pull voltage is applied to the at least one pull resistor, comparing the at least one loaded electrical characteristic with at least one predetermined value, and identifying a specification of the interface in accordance with the comparison. 
         [0008]    The present disclosure will be understood from the following description of exemplary embodiments, which is to be read in connection with the accompanying drawings. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The present disclosure presents an apparatus and method for discerning a host interface in accordance with the following exemplary figures, wherein like elements may be indicated by like reference characters, and in which: 
           [0010]      FIG. 1  shows a schematic block diagram for a conventional host to device interface system; 
           [0011]      FIG. 2  shows a schematic block diagram for a host to device interface system in accordance with an exemplary embodiment of the present disclosure; 
           [0012]      FIG. 3  shows a partial schematic circuit diagram of a host to device interface system for MMC, ISO or USB host interfaces in accordance with an exemplary embodiment of the present disclosure; 
           [0013]      FIG. 4  shows a partial schematic circuit diagram of a host to device interface system for generic host interfaces in accordance with an exemplary embodiment of the present disclosure; 
           [0014]      FIG. 5  shows a partial schematic circuit diagram of a host to device interface system for pull-up host interfaces in accordance with an exemplary embodiment of the present disclosure; and 
           [0015]      FIG. 6  shows a partial schematic circuit diagram of a host to device interface system for pull-down host interfaces in accordance with an exemplary embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0016]    The present disclosure presents an apparatus and method for host interface identification. Exemplary embodiments may discern the type of a host interface based on whether the host interface has a pull-up resistor, a pull-down resistor, a DC voltage, a ground voltage or a floating status. 
         [0017]    Turning to  FIG. 2 , an interface system in accordance with an exemplary embodiment of the present disclosure is indicated generally by the reference numeral  200 . The system  200  includes a host  212  and a device  216 . The host  212  includes a host includes a host interface  214 . The device  216  includes a host interface identifier  217 , an adaptable device interface  218  in signal communication with the host interface identifier, and a controller  220  in signal communication with the host interface identifier  217  and the adaptable device interface  218 . 
         [0018]    In operation, the device  216  is connected to the host  212 . The adaptable device interface  218  is adapted or reconfigured in accordance with the host interface identifier  217  to match the type of the host interface  214 . The host  212  and the device  216  communicate with each other via the host interface  214  and the adaptable device interface  218 . The host interface identifier  217  of the device  216  identifies the host interface  214  and outputs the identified result to the controller  220 . The controller  220  configures the corresponding adaptable device interface  218  based on the identified result. The host  212  and the device  216  communicate with each other via the host interface  214  and the adapted or configured device interface  218 . For example, a given host interface  214  might support only a Multi-Media Card (MMC), a Universal Serial Bus (USB), an ISO 7816 interface, or the like. 
         [0019]    Turning now to  FIG. 3 , an interface system in accordance with an exemplary embodiment of the present disclosure is indicated generally by the reference numeral  300 . The system  300  includes a host interface identifier  317  in signal communication with a connection unit  326 . The connection unit  326  is in switchable signal communication with one type of host at a time, including a first type  321  having a high voltage potential VDD connected to an Rpu pull-up resistor, a second type  322  having a high voltage potential VDD, a third type  323  having an open or floating voltage potential, a fourth type  324  having a low voltage potential VSS, and a fifth type  325  having a low voltage potential VSS connected to an Rpd pull-down resistor. 
         [0020]    The host interface identifier  317  includes an output terminal  328  in signal communication with a first switch SW 1 . The host interface identifier  317  may also have a voltage detector, such as a single transistor, in signal communication with the terminal  328 . The switch SW 1  is in signal communication with a first pull-up resistor Rpu 1 , which, in turn, is in signal communication with the high voltage potential VDD. The host interface identifier  317  further includes a second switch SW 2  in signal communication with the output terminal  328 . The switch SW 2  is in signal communication with a second pull-up resistor Rpu 2 , which, in turn, is in signal communication with the high voltage potential VDD. The host interface identifier  317  further includes a third switch SW 3  in signal communication with the output terminal  328 . The switch SW 3  is in signal communication with a first pull-down resistor Rpd 1 , which, in turn, is in signal communication with the low voltage potential VSS. In addition the host interface identifier  317  includes a fourth switch SW 4  in signal communication with the output terminal  328 . The switch SW 4  is in signal communication with a second pull-down resistor Rpd 2 , which, in turn, is in signal communication with the low voltage potential VSS. 
         [0021]    Thus, the host interface types  321  through  325  represent the characteristics of five different interface specifications. For example, the type  321  having VDD with pull-up represents the characteristics of an MMC interface, while the type  325  having VSS with pull-down represents that of a USB interface. The type  322  having VDD, the type  323  having floating voltage potential, and the type  324  having VSS represent those of ISO 7816 interfaces. 
         [0022]    In operation, the host interface identifier  317  measures voltages on the connection unit  326  when the host interface identifier  317  sequentially connects each of SW 1  through SW 4 , and then outputs the measured voltages to the controller  220  of  FIG. 2 . Reference is made to Table 1, which follows. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
             
             
               
                   
                   
               
               
                   
                 MMC 
                 USB 
                 ISO 7816 
               
             
          
           
               
                   
                 Pull-Up 
                 Pull-Down 
                 High-Z 
                 VDD 
                 VSS 
               
               
                   
                 (50–100K) 
                 (15K) 
                 (∞) 
                 (0) 
                 (0) 
               
               
                   
                   
               
             
          
           
               
                 Pull-Up(Rpu1) 
                 High 
                 Low 
                 High 
                 High 
                 Low 
               
               
                 (150K) 
                 (1) 
                 (0) 
                 (1) 
                 (1) 
                 (0) 
               
               
                 Pull-Up(Rpu2) 
                 High 
                 High 
                 High 
                 High 
                 Low 
               
               
                 (1.5K) 
                 (1) 
                 (1) 
                 (1) 
                 (1) 
                 (0) 
               
               
                 Pull-Down(Rpd1) 
                 High 
                 Low 
                 Low 
                 High 
                 Low 
               
               
                 (1M) 
                 (1) 
                 (0) 
                 (0) 
                 (1) 
                 (0) 
               
               
                 Pull-Down(Rpd2) 
                 Low 
                 Low 
                 Low 
                 High 
                 Low 
               
               
                 (5K) 
                 (0) 
                 (0) 
                 (0) 
                 (1) 
                 (0) 
               
               
                   
               
             
          
         
       
     
         [0023]    Thus, referring back to  FIG. 2  with reference to Table 1, the controller  220  compares the measured voltages with the predetermined voltage and determines the logic “High” or “Low”. For example, the predetermined voltage or cut-off between a “High” and a “Low” voltage potential may be defined as (VOD-VSS)/2+VSS. The controller  220  determines the host interface  212  based on the logic values from Table 1, and sets the corresponding device interface among a plurality of interfaces within the adaptable device interface  218 . 
         [0024]    For example, an MMC host interface uses a pull-up resistor Rpu between about 50K and about 100K ohms. A USB host interface uses a pull-down resistor Rpd of about 15K ohms. Thus, a preferred embodiment has Rpu 1 =150K ohms: Rpu 2 =5K ohms, Rpd 1 =1000K ohms, and Rpd 2 =5K ohms. 
         [0025]    As shown in  FIG. 4 , an interface system in accordance with another exemplary embodiment of the present disclosure is indicated generally by the reference numeral  400 . The system  400  includes a host interface identifier  417  in signal communication with a connection unit  426 . The connection unit  426  is in switchable signal communication with one host at a time. A first host  431  has a high voltage potential VDD connected to an Rpu_a pull-up resistor, a second host  432  has a high voltage potential VoD connected to an Rpu_b pull-up resistor, a third host  433  has a low voltage potential VSS connected to an Rpd_c pull-down resistor, and a fourth host  434  has a low voltage potential VSS connected to an Rpd_d pull-down resistor. Other hosts may each have one of pull-up resistors Rpu_c through Rpu_z: or one of pull-down resistors Rpd_c through Rpd_z for example. 
         [0026]    The host interface identifier  417  includes an output terminal  428  in signal communication with a switch SW 1 . The switch SW 1  is in signal communication with a first pull-up resistor Rpu 1 , which, in turn, is in signal communication with the high voltage potential VOD The host interface identifier  417  further includes switches SW 2  through SWN, each in signal communication with the output terminal  428 . The switches SW 2  through SWN are each in signal communication with a corresponding pull-up resistor of pull-up resistors Rpu 2  through RpuN, which, in turn, are in signal communication with the high voltage potential VDD. 
         [0027]    The host interface identifier  417  further includes a switch SW 1 ′. The switch SW 1 ′ is in signal communication with a first pull-down resistor Rpd 1  which, in turn, is in signal communication with the low voltage potential VSS. The host interface identifier  417  further includes switches SW 2 ′ through SWN′, each in signal communication with the output terminal  428 . The switches SW 2 ′ through SWN′ are each in signal communication with a corresponding pull-dowvn resistor of pull-down resistors Rpd 2 ′ through RpdN′, which, in turn, are in signal communication with the low voltage potential VSS. 
         [0028]    In one example, Rpu_a is greater than Rpu_b. Rpd 1  is greater than Rpu_a. Rpu_a is greater than Rpd 2 , which is greater than Rpu_b. When the pull-down resistor Rpd 1  is connected to the host interface, if the connection unit  426  is at a “High” voltage potential, the host interface might be either the pull-up  431  with Rpu_a or the pull-up  432  with Rpu_b, for example. When the pull-down resistor Rpd 2  is connected to the host interface, if the connection unit  426  is still “High”, the host interface is the pull-up  432  with Rpu_b. On the other hand, if the connection unit  426  is “Low” when the pull-down resistor Rpd 2  is connected to the host interface, the host interface is the pull-up  431  with Rpu_a. 
         [0029]    In another example Rpd_c is greater than Rpd_d. Rpu 1  is greater than Rpd_c. Rpd_c is greater than Rpu 2 , which is greater than Rpd_d. When the pull-up resistor Rpu 1  is connected to the host interface, if the connection unit  426  is “Low”, the host interface might be the pull-down  433  with Rpd_c or the pull-down  434  with Rpd_d. When the pull-up resistor Rpu 2  is connected to the host interface if the connection unit  426  is still “High”, the host interface is the pull-down  433  with Rpd_c. On the other hand, if the connection unit  426  is “Low” when the pull-up resistor Rpu 2  is connected to the host interface, the host interface is the pull-down  434  with Rpd_d. 
         [0030]    Thus, by using suitable pull-up resistors or pull-down resistors, embodiments of the present disclosure identify host interfaces that have various pull-up resistors or pull-down resistors. 
         [0031]    Turning to  FIG. 5 , an interface system in accordance with another exemplary embodiment of the present disclosure is indicated generally by the reference numeral  500 . The system  500  includes a host interface identifier  517  in signal communication with a connection unit  526 . The connection unit  526  is in signal communication with a host  531 , which has a high voltage potential VOD connected to a pull-up resistor Rpu_a. 
         [0032]    The host interface identifier  517  includes an output terminal  528  in signal communication with a switch SW 1 . The switch SW 1  is in signal communication with a first pull-up resistor Rpu 1 , which, in turn, is in signal communication with the high voltage potential VDD. The host interface identifier  517  further includes odd numbered switches SW 3  through SWm- 1 , each in signal communication with the output terminal  528 . The odd numbered switches SW 1  through SWm- 1  are each in signal communication with a corresponding pull-up resistor of pull-up resistors Rpu 1  through RpuN, which, in turn, are in signal communication with the high voltage potential VDD. Here, m=2N. 
         [0033]    The host interface identifier  517  further includes a switch SW 2 . The switch SW 2  is in signal communication with a first pull-down resistor Rpd 1 , which, in turn, is in signal communication with the low voltage potential VSS. The host interface identifier  517  further includes even numbered switches SW 4  through SWm, each in signal communication with the output terminal  528 . The even numbered switches SW 2  through SWm are each in signal communication with a corresponding pull-down resistor of pull-down resistors Rpd 1  through RpdN, which, in turn, are in signal communication with the low voltage potential VSS. 
         [0034]    Here, the connection unit  526  has a “Low” voltage potential when a pull-down resistor less than the pull-up resistor Rpu_a is connected to the host  531 . The connection unit  526  has a “High” voltage potential when a pull-down resistor greater than Rpu_a is connected to the host  531 . That is, the value of the Rpu_a exists between the two pull-down resistors where the connection unit  526  voltage potential changes from “High” to “Low”. 
         [0035]    Thus, this embodiment of the present disclosure can measure the value of a host pull-up resistor by sequentially connecting with smaller pull-down resistors to larger pull-down resistors in the host interface identifier  517 . In addition, it can measure the value of a host pull-down resistor by sequentially connecting with smaller pull-up resistors to larger pull-up resistors in the host interface identifier  517 . 
         [0036]    Turning now to  FIG. 6 , an interface system in accordance with another exemplary embodiment of the present disclosure is indicated generally by the reference numeral  600 . The system  600  includes a host interface identifier  617  in signal communication with a connection unit  626 . The connection unit  626  is in signal communication with a host  633 , which has a low voltage potential VSS connected to a pull-down resistor Rpd_c. 
         [0037]    The host interface identifier  617  includes an output terminal  628  in signal communication with a switch SW 1 . The switch SW 1  is in signal communication with a first pull-up resistor Rpu 1 , which, in turn, is in signal communication with the high voltage potential VDD. The host interface identifier  617  further includes odd numbered switches SW 3  through SWm- 1 , each in signal communication with the output terminal  528 . The odd numbered switches SW 1  through SWm- 1  are each in signal communication with a corresponding pull-up resistor of pull-up resistors Rpu 1  through RpuN, which, in turn, are in signal communication with the high voltage potential VDD. Here. m=2N. 
         [0038]    The host interface identifier  617  further includes a switch SW 2 . The switch SW 2  is in signal communication with a first pull-down resistor Rpd 1 , which, in turn, is in signal communication with the low voltage potential VSS. The host interface identifier  617  further includes even numbered switches SW 4  through SWm, each in signal communication with the output terminal  628 . The even numbered switches SW 2  through SWm are each in signal communication with a corresponding pull-down resistor of pull-down resistors Rpd 1  through RpdN, which, in turn, are in signal communication with the low voltage potential VSS. 
         [0039]    Here, the connection unit  626  has a “High” voltage potential when a pull-up resistor less than Rpd_c is connected to the host  633 . The connection unit  626  has a “Low” voltage potential when a pull-up resistor more than Rpd_c is connected to the host  633 . The value of the pull-down resistor Rpd_c exists between the pair of pull-up resistors where the connection unit  626  changes from a “High” to a “Low” voltage potential. 
         [0040]    Thus, this embodiment of the present disclosure can measure the value of a host pull-down resistor by sequentially connecting with smaller pull-up resistors to larger pull-up resistors in the host interface identifier  617 . In addition, it can also measure the value of a host pull-up resistor by sequentially connecting with smaller pull-down resistors to larger pull-down resistors in the host interface identifier  617 . 
         [0041]    It is to be understood that the teachings of the present disclosure may be implemented in various forms of hardware, software, firmware, special purpose processors, or combinations thereof. Moreover, the software is preferably implemented as an application program tangibly embodied in a program storage device. The application program may be uploaded to, and executed by, a machine comprising any suitable architecture. Preferably, the machine is implemented on a computer platform having hardware such as one or more central processing units (“CPU”), a random access memory (“RAM”), and input/output (“I/O”) interfaces. The computer platform may also include an operating system and microinstruction code. The various processes and functions described herein may be either part of the microinstruction code or part of the application program, or any combination thereof, which may be executed by a CPU. In addition, various other peripheral units may be connected to the computer platform such as an additional data storage unit and a display unit. The actual connections between the system components or the process function blocks may differ depending upon the manner in which the embodiment is programmed. 
         [0042]    Although illustrative embodiments have been described herein with reference to the accompanying drawings, it is to be understood that the present disclosure is not limited to those precise embodiments, and that various other changes and modifications may be effected therein by one of ordinary skill in the pertinent art without departing from the scope or spirit of the present disclosure. All such changes and modifications are intended to be included within the scope of the present disclosure as set forth in the appended claims.