Abstract:
A removable electronic device having an application module for transferring data to or from a host having a plurality of contact terminals, the device comprising a first row of contact pads, each of the contact pads of the first row including a substantially tapered end, and a second row of contact pads, each of the contact pads of the second row including a substantially tapered end that corresponds to the substantially tapered end of at least one of the contact pads of the first row in an interweaving relationship, wherein the first and second rows of contacts pads are configured to receive the plurality of contact terminals.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/607,344, filed Sep. 7, 2004, which is herein incorporated by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates generally to a removable electronic device and, more particularly, to a removable memory card standard and method thereof.  
         [0003]     A memory card is commonly known as a small portable package containing digital memory, such as an array of non-volatile memories, such as flash memories, EPROMs, or EEPROMs (electrically erasable and programmable read only memory). Memory cards have gain popularity as a device for storing a substantial amount of bytes of data from personal computers, notebook computers, personal electronic assistants, cellular telephones, cameras and other electronic devices that support removable data storage.  
         [0004]     In general, a memory card includes exposed electrical contacts on its surface to allow easy connection to and removal from a receptacle of a host electronic system or device, particularly portable devices. A number of standards for a memory card have been implemented, including the MultiMedia Card (“MMC”) by the MultiMedia Card Association (“MMCA”) of Cupertino, California. An MMC is a compact, removable memory card for storing and retrieving digital information in small, low power devices. MMC has been used in many mobile electronic applications, such as music players, mobile phones, personal digital assistants (PDAs), digital cameras, voice recorders, and GPS navigation devices. The MMCA developed and regulated its open industry standards, and also defined all types of MMCs as an industry standard across multiple host platforms and markets. The physical and electrical specifications for the MMC are given in “The MultiMediaCard System Specification” that is updated and published from time-to-time by the MMCA.  
         [0005]     Another known standard for a removable memory card, although not limited to memory storage, is the Universal Serial Bus (“USB”). USB is a high-speed serial bus that supports devices such as printers, keyboards, scanners, pointing devices, and PDAs. USB has become a standard within the computer industry as this protocol affords networking of multiple devices with minimal connections and increased user friendliness. USB is currently defined by the Universal Serial Bus Specification, written and controlled by USB Implementers Forum, Inc., a non-profit corporation founded by a group of companies that developed the USB specification. The specification covers all aspects of USB operations, including electrical, mechanical, and communications characteristics and specifications. One significant feature of the USB is that it allows a peripheral device to store information about itself, and to provide such information upon request by the host. This obviates the need for the host, be it a computer, operating system, or application program, to maintain this information for many different devices. Instead, the device itself stores and provides the information.  
         [0006]     In the evolution of memory cards, it is desirable to have memory cards that consumes low power and provides higher speed for accessing, while still retaining backward compatibility with existing protocols such as the MMC and USB specifications.  
       BRIEF SUMMARY OF THE INVENTION  
       [0007]     A novel removable memory card standard is disclosed. The standard of the present invention includes both detection schemes and hardware interface compatibility requirements. Furthermore, the novel standard is backward compatible with the MMC and USB applications.  
         [0008]     In accordance with an embodiment of the present invention, there is provided a removable electronic device having an application module for transferring data to or from a host having a plurality of contact terminals, the device comprising a first row of contact pads, each of the contact pads of the first row including a substantially tapered end, and a second row of contact pads, each of the contact pads of the second row including a substantially tapered end that corresponds to the substantially tapered end of at least one of the contact pads of the first row in an interweaving relationship, wherein the first and second rows of contacts pads are configured to receive the plurality of contact terminals.  
         [0009]     Further in accordance with the present invention, there is provided a removable electronic device having an application module for transferring data to or from a host, the device comprising a housing having a top surface, a bottom surface and a periphery, a plurality of rows of interweaving contact pads formed on the top surface of the housing, a substantially U-shaped indentation on the periphery of the housing, and a notch on a corner of the housing for securing the device to the host when the device is connected to the host.  
         [0010]     Also in accordance with the present invention, there is provided a removable electronic device having an application module for transferring data to or from a host, the device comprising a housing having a top surface, a bottom surface and a periphery, a substantially U-shaped indentation on the periphery of the housing, and a notch on a corner of the housing for securing the device to the host when the device is connected to the host.  
         [0011]     Still in accordance with the present invention, there is provided a removable electronic device having an application module for transferring data to or from a host, the device comprising a housing having a top surface, a bottom surface and a periphery, a plurality of rows of interweaving contact pads formed on the top surface of the housing, and a substantially U-shaped indentation on the periphery of the housing.  
         [0012]     Yet still in accordance with the present invention, there is provided a removable electronic device having an application module for transferring data to or from a host, the device comprising a housing having a top surface, a bottom surface and a periphery, a plurality of rows of interweaving contact pads formed on the top surface of the housing, and a notch on a corner of the housing for securing the device to the host when the device is connected to the host.  
         [0013]     Additional features and advantages of the present invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The features and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.  
         [0014]     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.  
         [0015]     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one embodiment of the present invention and together with the description, serves to explain the principles of the invention. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0016]     The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.  
         [0017]     In the drawings:  
         [0018]      FIGS. 1A, 1B  and  1 C are functional block diagrams of the general applications of a memory card in accordance with one embodiment of the present invention;  
         [0019]      FIG. 2  is a flow diagram of a method for detecting a mode of operation in accordance with one embodiment of the present invention;  
         [0020]      FIG. 3  is another flow diagram of a method for detecting a mode of operation in accordance with one embodiment of the present invention;  
         [0021]      FIG. 4A  is a proposed pin assignment chart of a removable electronic device in accordance with one embodiment of the present invention;  
         [0022]      FIG. 4B  is a proposed pin assignment chart of a removable electronic device in accordance with another embodiment of the present invention;  
         [0023]      FIG. 5  is a diagram of a removable electronic device in accordance with one embodiment of the present invention; and  
         [0024]      FIGS. 6A and 6B  show exemplary electronic devices in accordance with embodiments of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0025]     In this detailed description, for purposes of explanation, numerous specific details are set forth to provide a thorough understanding of embodiments of the present invention. One skilled in the art will appreciate, however, that embodiments of the present invention may be practiced without these specific details. In other instances, structures and devices are shown in block diagram form. Furthermore, one skilled in the art can readily appreciate that the specific sequences in which methods are presented and performed are illustrative and it is contemplated that the sequences can be varied and still remain within the spirit and scope of embodiments of the present invention.  
         [0026]      FIGS. 1A, 1B  and  1 C are functional block diagrams of general applications of a removable electronic device  30  in accordance with one embodiment of the present invention. Electronic device  30 , tentatively named the “Mu Card,” which is able to support modes of operations compatible with USB and at least one of MMC, CF (compact flash), SM (smart media) and SD (security digital) applications. For example, the USB compatible mode includes USB 2.0 application, and the MMC compatible mode includes one of MMC 4.0 or MMC SPI (serial-peripheral interface) applications. For the purpose of simplicity, only the MMC compatible mode is illustrated in the following embodiments. Skilled persons in the art will understand that the present invention is equally applicable to the CF, SM and SD modes.  
         [0027]     Electronic device  30  includes a 1-, 4-, 8- or 16-bit interface, and provides low voltage support of 5V/3.3V/11.8V, with zero power consumption during standby. In addition, electronic device  30  is able to support a wide bandwidth from approximately 50 KB/s to 120 MB/s. In contrast, MMC 4.0 supports 1-, 4- or 8-bit data transfer at a maximum speed of 52 MB/sec, and USB 2.0 supports data transfer at a maximum speed of 60 MB/sec. Consequently, electronic device  30  provides high-speed applications while retaining backward compatibility at least with regard to USB, MMC and MMC SPI applications.  
         [0028]      FIG. 1A  is a functional block diagram of electronic device  30  operating in a USB mode. Referring to  FIG. 1A , electronic device  30  includes an interface (IF) mode detector  32 , a multi-media card (MMC) device controller  34 , a wrapper  35 , a universal serial bus (USB) physical layer (PHY) circuit  36 , a USB device controller  37 , and an application module  38 . IF mode detector  32  detects a mode of operation to distinguish among an MMC mode, a USB mode or a Mu mode when electronic device  30  is inserted into a host  40 . Host  40 , for example, a notebook, a personal computer (PC), a cell phone, a tablet PC, a PDA or a DV/DSC, may include a card reader (not shown) for receiving electronic device  30 . In the present embodiment, IF mode detector  32  detects whether a host  40 , to which electronic device  30  is connected, is in compliance with the USB specifications. USB device controller  37  controls data transfer over a common bus  42  between host  40  and application module  38  via USB PHY circuit  36 . Application module  38  functions to serve as a memory storage or an input/output (I/O) interface, depending on the operation mode detected.  
         [0029]      FIG. 1B  is a functional block diagram of electronic device  30  operating in a Mu mode. Referring to  FIG. 1B , IF mode detector  32  detects that a host  40 , to which electronic device  30  is connected, is in compliance with the Mu specifications. USB device controller  37  controls data transfer between host  40  and application module  38  via wrapper  35 . Wrapper  35 , which wraps a call to a function or program inside another function or program, functions to convert 16-bit data into serial data recognizable by USB device controller  37 , or vice versa. As such, wrapper  35  functions to bridge between a Mu bus and a UTMI (USB 2.0 Transceiver Macrocell Interface) bus. UTMI, which has been developed to define the interface specifications of the physical layer circuits and part of the logical layer circuits of the USB 2.0, enables a data transfer rate of 480 Mbps in high speed (HS) mode, which is significantly higher than that of the USB 1.1, while maintaining backward compatibility with the USB 1.1 standard.  
         [0030]      FIG. 1C  is a functional block diagram of electronic device  30  operating in an MMC mode. Referring to  FIG. 1C , IF mode detector  32  detects that a host  40 , to which electronic device  30  is connected, is in compliance with the MMC specifications. MMC device controller  34  controls data transfer between host  40  and application module  38 . The MMC application includes one of MMC 4.0, a 1-, 4- or 8-bit interface, or MMC SPI, a 1-bit interface.  
         [0031]      FIG. 2  is a flow diagram of a method for detecting a mode of operation in accordance with one embodiment of the present invention. Referring to  FIG. 2 , on the device side, host  40  to which electronic device  30  is connected is turned on at step  50 . The power source voltage, VDD, for host  40  is detected at step  52  to determine whether the VDD is equal to or greater than a voltage level a USB application requires. Normally, a USB application is operated at a voltage level ranging from approximately 4.5V (volts) to 5.5V, while an MMC or an Mu application is operated at a voltage level of approximately 1.8V or 3.3V. In one embodiment, if the VDD level for host  40  is equal to or greater than 4.4V, a determination is made at step  54  that the mode of operation is USB 2.0. If the VDD level for host  40  is smaller than 4.4V, a determination is made that the mode of operation is either a Mu application or an MMC application.  
         [0032]     Next, a determination is made at step  56  whether a command signal CMD 0  sent from host  40  is received by electronic device  30 . Detection of the command signal CMD 0  is performed within a predetermined time period at step  58 . If the predetermined time expires, host  40  is turned off, or “timed out” to save power at step  60 . If the predetermined time does not expire, the detection of the command signal continues. When a command signal is received, a determination is made at step  62  whether the command signal indicates a Mu application. If the command signal is not a Mu command signal, a determination is made at step  64  that the mode of operation is an MMC application. If the command signal is determined to be a Mu command signal, electronic device  30  responds to host  40  that the mode of operation is a Mu application at step  66 . Electronic device  30  then waits for a predetermined time, for example, 8 clocks, at step  68  for synchronization. Generally, the clock rate depends on the speed of host and system clocks. Electronic device  30  then switches at step  70  to a Mu interface for a Mu application at step  72 .  
         [0033]      FIG. 3  is another flow diagram of a method for detecting a mode of operation in accordance with one embodiment of the present invention. Referring to  FIG. 3 , at the host side, host  40  sends a Mu command signal Mu CMD 0  to electronic device  30  at step  80 . If electronic device  30  at step  82  does not send a response signal, host  40  sends an MMC command signal MMC CMD 0  at step  84 , indicating that the mode of operation is the MMC application at step  86 . If electronic device  30  at step  82  replies with a Mu response signal, host  40  sends a predetermined number of clocks, for example, 8 clocks, for synchronization at step  88 . Electronic device  30  switches at step  90  to the Mu mode. At step  92 , electronic device  30  may optionally send a signal to host  40 , indicating that a Mu interface is ready.  
         [0034]     By way of example, the command signals MMC CMD 0  and Mu CMD 0  are defined in a 6-byte format as “40h, 00h, 00h, 00h, 00h, 95h” and “40h, 4Dh, 55h, BFh, B2h, AAh,” respectively. Furthermore, the Mu response signal is defined in a 6-byte format as “19h [4-byte operating parameters] FFh.” 
         [0035]      FIG. 4A  is a proposed pin assignment chart of a removable electronic device in accordance with one embodiment of the present invention. Referring to  FIG. 4A , all of the pins at the device side are kept as HiZ (high impedance) state until a mode of operation between a host and the removable electronic device is determined. The first pin of the removable electronic device for the MMC 4.0 mode, i.e., DAT 3, is defined to switch the MMC 4.0 mode to the MMC SPI mode, which has been defined in the MMC Specification. The second pin for the Mu interface mode, i.e., DAT 8, is used to identify that the MMC mode or Mu interface mode is selected. The fourteenth and fifteenth pins for the USB mode, i.e., D+ and D−, are a pair of data signals, which may be used to determine whether the USB mode is selected. The pair of data signals (D+, D−) is a complementary pair in which one is at a high level when the other is at a low level. Pins  18 ,  19  and  20  are reserved for SIMM (single in-line memory module) card applications. Thus, the removable electronic device of the present invention is able to support MMC compatible, USB compatible and Mu-interface applications, and simultaneously retains the flexibility of working for the SIMM applications.  
         [0036]     An exemplary interface protocol of the present invention is described as follows:  
         [0037]     1. SYNC Field  
         [0038]     (1) 1-bit: DAT[3:0]=0b  
         [0039]     (2) 4-bit: DAT[3:0]=xxx0b  
         [0040]     (3) 8-bit: DAT[7:0]=xxxxxxx0b  
         [0041]     (4) 16-bit: DAT[15:0 =xxxxxxxxxxxxxxx0b  
         [0000]     Where “x” refers to a condition that is not relevant for the protocol.  
         [0042]     2. PID Field  
         [0043]     (1) 1-bit: LSB first 
        DAT=PID[0] PID[1] PID[2] PID[3] nPID[0] nPID[1] nPID[2] nPID[3]       
 
         [0045]     (2) 4-bit: 
        DAT[3:0]=PID[3:0] nPID[3:0]       
 
         [0047]     (3) 8-bit: 
        DAT[7:4]=inverted of PID[3:0]    DAT[3:0]=PID[3:0]       
 
         [0050]     Where “nPID” refers to an inverted signal of PID. The PID Data transaction is protected by the inverted mirror Data of PID and nPID. The controller in both the host and device sides should verify the validity of the PID. PID Codes are defined in Table 1 given below.  
                                 TABLE 1                           PID Codes            PID Type   PID Name   PID&lt;3:0&gt;*   Description               Token   OUT   0001B   Address + endpoint number in                   host-to-function transaction           IN   1001B   Address + endpoint number in                   function-to-host transaction           SOF   0101B   Start-of-Frame marker and frame                   number           SETUP   1101B   Address + endpoint number in                   host-to-function transaction for                   SETUP to a control pipe       Data   DATA0   0011B   Data packet PID even           DATA1   1011B   Data packet PID odd           DATA2   0111B   Date packet PID high-speed,                   high bandwidth isochronous                   transaction in a microframe                   (see Section 5.9.2 for more                   information)           MDATA   1111B   Data packet PID high-speed for                   split and high bandwidth                   isochronous transactions (see                   Sections 5.9.2, 11.20, and                   11.21 for more information)       Handshake   ACK   0010B   Receiver accepts error-free                   data packet           NAK   1010B   Receiving device cannot accept                   data or transmitting                   device cannot send data           STALL   1110B   Endpoint is halted or a control                   pipe request is not supported           NYET   0110B   No response yet from receiver                   (see Sections 8.5.1 and                   11.17-11.21)       Special   PRE   1100B   (Token) Host-issued preamble.                   Enables downstream bus                   traffic to low-speed devices.           ERR   1100B   (Handshake) Split Transaction                   Error Handshake (reuses                   PRE value)           SPLIT   1000B   (Token) High-speed Split                   Transaction Token (see                   Section 8.4.2)           PING   0100B   (Token) High-speed flow                   control probe for a                   bulk/control endpoint                   (see Section 8.5.1)           Reserved   0000B   Reserved PID                 *Note:            PID bits are shown in MSb order. When sent on the USB, the rightmost bit (bit 0) will be sent first.             
 
         [0051]     3. Address, End Point, CRC5 Field  
         [0052]     (1) Address=&gt;7-bit, ADDR[6:0] 
         [0053]     (2) End Point=&gt;4-bit, EndP[3:0] 
         [0054]     (3) Token CRC=&gt;5-bit, TCRC[4:0]
        {ADDR[6:0] &amp; EndP[3]}+{EndP[2:0] &amp; TCRC[4:0]}
 
 Where TCRC is a 5-bit Token CRC, and the CRC on the Mu card is optional. If CRC is turned on, the CRC check must exist on both of the host and device. If, however, CRC is disabled, Wrapper must generate a CRC for a USB controller. Since Default is disabled CRC, there is no CRC field when CRC is disabled. 
       
 
         [0056]     4. EOP Field  
         [0057]     (1) 1-bit: DAT0=1b  
         [0058]     (2) 4-bit: DAT[3:0]=xxx1b  
         [0059]     (3) 8-bit: DAT[7:0 =xxxxxxx1b  
         [0060]     (4) 16-bit: DAT[15:0]=xxxxxxxxxxxxxxx1b  
         [0061]     Where “x” refers to a “don&#39;t care” condition. For solving an even/odd byte issue on the 16-bit mode transaction, OddByte bit is added on the b [15] of the EOP field. If OddByte=1, then the last byte on the DATA [15:8] is invalid. If OddByte=0, then the last word on the DATA [15:0] is valid.  
         [0062]     5. Token Packet Format  
         [0063]     Token Packet is composed of 3-byte SYNC and EOP. The Token packet supports at least the 1-bit, 4-bit and 8-bit modes.  
         [0064]     (1) 1-bit: (LSB First) 
        SYNC+PID+ADDR+ENDP+CRC5+EOP        
 
         [0066]     (2) 4-bit: {DAT[3:0]}
        SYNC+PID+not(PID)+A[3:0+{ENDP[0] &amp; A[6:4]}+{CRC0 &amp; ENDP[3:1]}+CRC[5:1]+EOP        
 
         [0068]     (3) 8-bit mode: {DAT[7:0]}
        SYNC+{not(PID) &amp; PID}+{EP[0] &amp; A[6:0]}+{TCRC[4:0] &amp; EP[3:1]}+EOP        
 
         [0070]     5.1. Start-of-Frame Format 
        SYNC+{not(PID) &amp; PID}+{FN[10:3]}+{FN[2:0] &amp; TCRC[ 4:0]}+EOP          
 
         [0072]     Where FN refers to Frame Number.  
                                                                                                                                         6. DATA PACKET FORMAT                                    6.1. Data Field Format                (i) 1-bit: (LSB first)                                                                                               (ii) 4-bit                                                                                               (iii) 8-bit                                                                                               (iv) 16-bit                                                                                               Where the 16-bit mode is used only in Data Packet.           6.2. Data Packet Format           SYNC + {not(PID) &amp; PID} + {DAT[7:0]}*(0˜1024) +           {DCRC[15:8]} +            {DCRC[7:0]} + EOP       Where DCRC is Data CRC with 16-bit Polynomial:       X 16 +X 15 +x 2 +1 (SEED = 800Dh)                  
 
         [0073]     7. Handshake Packet Format  
         [0074]     (1) 1-bit: (LSB First) 
        SYNC+PID+EOP        
 
         [0076]     (2) 4-bit: {DAT[3:0]}
        SYNC+PID+not(PID)+EOP        
 
         [0078]     (3) 8-bit mode: {DAT[7:0]}
        SYNC+{not(PID) &amp; PID}+EOP        
 
         [0080]     8. Special Packet Format  
         [0081]     8.1. Ping Format  
         [0082]     (i) 1-bit: (LSB First) 
        SYNC+PID+ADDR+ENDP+CRC5+EOP        
 
         [0084]     (ii) 4-bit: {DAT[3:0]}
        SYNC+PID+not(PID)+A[3:0]+{ENDP[0] &amp; A[6:4]}+{CRC0 &amp; ENDP[3:1]}+CRC[5:1+EOP        
 
         [0086]     (iii) 8-bit mode: {DAT[7:0]}
        SYNC+{not(PID) &amp; PID}+{EP[0] &amp; A[6:0]}+{TCRC[4:0] &amp; EP[3:1]}+EOP        
 
         [0088]     9. Transfer Types  
         [0089]     The Transfer Types are inherent from the USB standard, including (1) Control, (2) Interrupt, (3) Bulk, and (4) Isochronous.  
         [0090]     10. Signal Integrity  
         [0091]     A signal or data transportation in the bus has 3 kinds of protections:  
         [0092]     (1) PID is protected by inverted mirror of PID and nPID. Where the nPID is an inverted signal of PID.  
         [0093]     (2) Token Packet and Start-of-Frame are protected by CRC5, of which the Polynomial and the seed are as follows: 
 
X 5 +X 2 +1 with SEED=01100b 
 
         [0094]     (3) Data Packet is protected by CRC16, of which the Polynomial and the seed are as follows: 
 
X 16 +X 15 +X 2 +1 with SEED=800Dh 
 
         [0095]     11. Bus Width and Setting  
         [0096]     The device is powered at the 1-bit bus mode. The host can set the bus width of 1-bit (initial), 4-bit, 8-bit, or 16-bit to be operated on both sides.  
         [0097]     (1) 1-bit: Token (1-bit), Handshake (1-bit), Special (1-bit), Data (1-bit).  
         [0098]     (2) 4-bit: Token (4-bit), Handshake (4-bit), Special (4-bit), Data (4-bit).  
         [0099]     (3) 8-bit: Token (8-bit), Handshake (8-bit), Special (8-bit), Data (8-bit).  
         [0100]     (4) 16-bit: Token (8-bit), Handshake (8-bit), Special (8-bit), Data (16-bit).  
         [0101]      FIG. 4B  is a proposed pin assignment chart of a removable electronic device in accordance with another embodiment of the present invention. Unlike the 20-pin assignment for a 16-bit application illustrated in  FIG. 4A ,  FIG. 4B  illustrates a 13-pin assignment for an 8-bit application. The eleventh and twelfth pins for the USB mode, defined for D− and D+, respectively, are used to determine whether the USB mode is selected. Furthermore, pins  11 ,  12  and  13  are defined for SIMM card applications.  
         [0102]      FIG. 5  is a diagram of a removable electronic device  100  in accordance with one embodiment of the present invention. Referring to  FIG. 5 , electronic device  100  includes a notch  102  on the upper left-hand corner to prevent incorrect insertion of electronic device  100 . In addition, notch  102  and related counter parts serve to allow for backward compatibility of MMC and USB applications, but not vice versa. In one aspect, notch  102  intersects the adjacent sides  104  and  106  with substantially the same angle, approximately  45  degrees.  
         [0103]     Electronic device  100  also includes a plurality of interweaving contact pads labeled  1  to  20 , which correspond to the pins illustrated in  FIG. 4A . The interweaving design in the contact pads allows additional pins to be present in the same real estate. As a result, a different number of contact pads may alternately be used. The contact pads, connected with a memory circuit chip (not shown) within electronic device  100 , are positioned in twenty recesses on a top surface along front side  104  and notch  102 . The contact pads may be divided into a first row and a second row. Each of the contact pads includes a substantially tapered end such that contact pads of the first row are arranged with the corresponding contact pads of the second row by their substantially tapered ends. The substantially tapered ends allow smooth contact with the host&#39;s contact terminals.  
         [0104]      FIGS. 6A and 6B  are diagrams of a removable electronic device  120  in accordance with another embodiment of the present invention.  FIG. 6A  is a top view of electronic device  120  having a housing (not numbered). Referring to  FIG. 6A , the housing includes a top surface, a bottom surface and a periphery. Electronic device  120  includes a notch  122  and a substantially “U-shaped” indentation  124  on the periphery of the housing to allow for a low-profile design. Specifically, indentation  124  allows a card reader (not shown) in the host to grasp electronic device  120  and secure electronic device  120  through indentation  124 , as opposed to the conventional application of using the bulk of the memory card to secure its position in the host. As such, the notch design of the memory card of the present invention obviates this consideration in the memory card design and in turn allows the design of the memory card to be minimized. Accordingly, the profile of the card reader in the host may also be minimized.  
         [0105]     In addition to a plurality of interweaving contact pads (not numbered) positioned in a first row and a second row, electronic device  120  includes a contact pad  128  extending across the first row to the second row. In one embodiment, the total number of the first row of contact pads and the second row of contact pads is 20.  
         [0106]      FIG. 6B  is a bottom view of electronic device  120 . Referring to  FIG. 6B , electronic device  120  includes additional indentations  126  on the periphery to allow for locking of electronic device  120  to the housing at the host side.  
         [0107]     It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.