Abstract:
A memory device may include a controller and a plurality of flash memory dice. The controller is provided for read and write access and communications with a host. However, the controller may also be utilized to test one or more of the flash memory dice mounted on the device. In this way, testing may be achieved with a relatively modestly priced tester by making use of the capabilities of the onboard controller. As a result, the cost of a memory device may be reduced in some cases.

Description:
BACKGROUND  
       [0001]     This invention relates generally to testing integrated circuits and, particularly, to testing removable flash memory devices.  
         [0002]     Removable flash memory devices may be utilized to transfer data from one location to another. Examples of removable memory devices include Universal Serial Bus (USB) flash drives, multi-media cards (MMC), secure digital cards (SD), memory stick cards, and xD picture cards, to mention a few examples.  
         [0003]     Generally, these devices plug into a host and act as a storage medium for the host. Then, the device may be unplugged, taken to another location, plugged into another host, and the data stored thereon read so that the data can be transferred from host to host. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0004]      FIG. 1  is an enlarged, cross-sectional view of a removable memory device under test;  
         [0005]      FIG. 2  is a depiction of a removable memory device in accordance with one embodiment of the present invention;  
         [0006]      FIG. 3  is a flow chart for a test methodology in accordance with one embodiment of the present invention; and  
         [0007]      FIG. 4  is a flow chart for implementing one embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0008]     Referring to  FIG. 1 , a basic test device  16  may be coupled to a removable memory device  14  through a suitable interposer or interconnection device  18 . The interposer or interconnection device  18  may be a cable, a set of contacts, a socket, a probe card, or other interposing or interconnecting devices.  
         [0009]     The test device  16  may be a very basic tester which may be a low cost tester in some embodiments. The test device  16  need only provide power and a few minimal commands to the removable memory device  14 . Since conventional testers are more elaborate and more expensive, cost savings may be achieved through the use of a relatively low cost tester.  
         [0010]     Referring to  FIG. 2 , the interconnection device  18  may be coupled to the removable memory device  14  by a connector  20 . In one embodiment, the connector  20  may be a Universal Serial Bus connector. However, any connector which allows a pluggable connection to the tester would be useful in some embodiments of the present invention.  
         [0011]     Removable memory device  14  may include a card  22  on which is mounted a microcontroller  24 . The microcontroller  24  may communicate with the connector  20  to receive or send signals. The controller  24 , in turn, is coupled to a first known good flash memory die  26 . This is a flash memory die that has undergone complete electrical testing (using more expensive testers than the basic test device  16 ) and is known to be functional. Also coupled to the controller  24  are one or more additional candidate dice  28   a,    28   b,  and  28   c.  These dice have not been completely tested prior to assembly on the card  22 . While three such devices are shown in the illustrated embodiment, any number of such dice may be provided. The untested memory may be memory that has had limited testing, for example, some testing may have been performed on the memory, such as testing for opens and shorts, or basic functionality.  
         [0012]     In accordance with some embodiments of the present invention, the test device  16  uses the controller  24  to electrically test, or to complete the testing of, the candidate dice  28 . Thus, if none of the flash candidate dice  28  are functional (the worst case), the removable memory device  14  may be sold at a price that accounts for the fact that the device only has one functional memory die.  
         [0013]     If one known good die were not included on the card  22 , then the controller  24 , printed circuit board, and other peripherals would be wasted as well if no die passed the electrical test. Thus, it is cost effective to provide one known good die  26 , which has been thoroughly tested, on the same card  22  with the controller  24 , to ensure that the card  22  and the controller  24  are still saleable, even if the candidate dice  28  are non-functional.  
         [0014]     Referring to  FIG. 3 , the test sequence for the test device  16  is to power up, as indicated in block  32 , then initiate the test of one of the dice  28 , as indicated in block  34 . It initiates the test by providing basic commands for the microcontroller  24  which then actually implements the test. The tester  16  also receives the results (block  36 ) of the test from the controller  24  over the connector  20  in some cases.  
         [0015]     A process used by the controller  24 , such as the one shown in  FIG. 4 , may be implemented in hardware, software, or firmware. If the process is implemented in software, that software may be stored on the controller  24  or on the known good memory die  28 , as two examples.  
         [0016]     Initially, the controller  24  receives the test command (block  40 ) from the test device  16 . In one embodiment, the test command may be as simple as a power up signal to the controller  24 . The controller  24  may then execute code from the known good memory die  28  that establishes that, on initial power up, the candidate dice  28  are to be tested. On ensuing power up sequences, no such test may be done in some embodiments. Code pre-stored, for example on the known good die  26 , may also give the addresses of the candidate dice  28  in one embodiment. In response to a signal from the test device  16 , a test of the first candidate die  28   a  is initiated as indicated in block  42 .  
         [0017]     The controller  24  then may store the results of that test as indicated in block  44 . At diamond  46 , a check determines whether there is another candidate die on the card  22 . If so, the next candidate die is tested. The sequence iterates until all of the dice  28  have been tested. Once there are no more candidate dice to be tested, as determined in diamond  46 , the test results that have been stored by the controller  24  are transferred to the host, such as the tester  16 , as indicated in block  48 . Then, the test device  16 , in one embodiment, merely turns off the controller  24 . Thus, in one embodiment, all the test device  16  needs to do is turn on and off the controller  24 . For example, a code may be reset or changed after initial power up to indicate thereafter that the dice  28  do not need to be tested.  
         [0018]     Because the testing cost tends to be a major component of the cost of removable memory devices, by using the onboard controller  24  as the tester, significant cost savings may be achieved. This is because a much less expensive tester is utilized. The controller  24  is needed in any case for receiving commands from the host and reading data from and writing data to the flash memory in normal operation.  
         [0019]     Once the test is complete, the tester  16  can appropriately bin the card  22 . For example, depending on the storage capacity of the dice that are functional, the removable memory card  14  may be binned and priced accordingly.  
         [0020]     References throughout this specification to “one embodiment” or “an embodiment” mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one implementation encompassed within the present invention. Thus, appearances of the phrase “one embodiment” or “in an embodiment” are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be instituted in other suitable forms other than the particular embodiment illustrated and all such forms may be encompassed within the claims of the present application.  
         [0021]     While the present invention has been described with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.