Abstract:
A device for extending functions of a computer connected thereto adds a new function to functions of an existing extension unit. The device includes a non-volatile memory and a new extension unit connected to the non-volatile memory and capable of being connected to the computer via a bus and to the existing extension unit. The new extension unit transfers what is stored in the non-volatile memory to the computer when the computer requests attribute information of the existing extension unit.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a device for adding a new function to a computer so as to extend functions of the computer. 
     2. Description of the Related Art 
     FIG. 5 is a block diagram showing a skeleton structure of a personal computer. 
     A configuration of FIG. 5 includes a CPU  1 , a PCI bus  2 , and an extension device  3 . The extension device  3  is connected to the PCI bus  2  for the purpose of extending functions of the personal computer. 
     The extension device  3  adds functions thereof to the personal computer. When a new function needs to be added to the extension device  3  to create a new extension device having the new function and the existing functions, two different schemes are available to achieve this object. In a first scheme, a new extension device  4  is simply a modified version of the extension device  3  as shown in FIG.  6 . In a second scheme, a new extension device  7  is a combination of the old extension device  3  and a new extension device  5  connected together via a PCI bus  6 , as shown in FIG.  7 . 
     The extension device  4  of the first scheme is generated by modifying the old extension device  3 , so that the extension device  4  has new attribute information  4 A assigned thereto. The extension device  7  of the second scheme includes the old extension device  3 , so that the new extension device  5  is provided with attribute information  3 A of the old extension device  3 . 
     Since the extension device  4  of the first scheme is created by modifying the extension device  3 , development of the extension device  4  involves redesigning of a entire device configuration. This results in a lengthy development period. 
     The extension device  7  of the second scheme is a combination of the old extension device  3  and the new extension device  5 , so that the extension device  3  can be used as it is without making any modification to its design. Development of the extension device  7  involves only the development of the new extension device  5 , and, thus, can be finished in a shorter time period. The configuration of the second scheme, however, has a drawback as lacking universal applicability in that new functions need to be specially adapted to the old extension device  3 . 
     Accordingly, there is a need for an extension device which can provide both old functions of an old extension device and new functions of a new extension device, and can offer universal applicability while requiring a relatively short time period for design and development. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is a general object of the present invention to provide an extension device which can satisfy the need as described above. 
     It is another and more specific object of the present invention to provide an extension device which can provide both old functions of an old extension device and new functions of a new extension device, and can offer universal applicability while requiring a relatively short time period for design and development. 
     In order to achieve the above objects according to the present invention, a device for extending functions of a computer connected thereto by adding a new function to functions of an existing extension device includes a non-volatile memory that is a rewrite-enable memory, and a new extension device connected to the non-volatile memory and capable of being connected to the computer via a bus and to the existing extension device, said new extension device transferring what is stored in said non-volatile memory to the computer when the computer requests attribute information of the existing extension device. 
     Since the existing extension device described above can be used without making any modification to its design, development of the whole device involves only the development of the new extension device. This results in the development being completed in a relatively short time period. Further, the device of the present invention is provided with the write-enable memory. When there is a need to replace the existing extension device with another extension device, modifying the attribute information in the write-enable memory is all that is necessary to cope with the new configuration. Therefore, universal applicability is insured. 
     According to another aspect of the present invention, a device for extending functions of a computer connected thereto by adding a new function to functions of an existing extension device includes a bus capable of having the existing extension device connected thereto, and a new extension device connected to the bus and capable of being connected to the computer via another bus, said new extension device transferring a request for attribute information sent from the computer to said existing extension device, and transferring the attribute information sent from the existing extension device to the computer. 
     Since the existing extension device described above can be used without making any modification to its design, development of the whole device involves only the development of the new extension device. This results in the development being completed in a relatively short time period. Further, the new extension device issues a request for attribute information to the existing extension device when the host computer requests the attribute information of the existing extension device, and receives the attribute information from the existing extension device to send it to the host computer on behalf of the existing extension device. Because of this configuration, even when another extension device having different attribute information is provided in place of the existing extension device, no design change is necessary in the circuit of the new extension device. Therefore, universal applicability is insured. 
     Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram showing a relevant portion of a personal computer and an extension device according to a first embodiment of the present invention; 
     FIG. 2 is a block diagram showing a relevant portion of a personal computer and an extension device according to a second embodiment of the present invention; 
     FIG. 3 is a block diagram showing a relevant portion of a personal computer and an extension device according to a third embodiment of the present invention; 
     FIG. 4 is a block diagram showing a relevant portion of a personal computer and an extension device according to a fourth embodiment of the present invention; 
     FIG. 5 is a block diagram showing a skeleton structure of a personal computer; 
     FIG. 6 is a block diagram showing a relevant portion of a personal computer and a related-art extension device connected to the personal computer; and 
     FIG. 7 is a block diagram showing a relevant portion of a personal computer and another related-art extension device connected to the personal computer. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following, embodiments of the present invention will be described with reference to the accompanying drawings. 
     FIG. 1 is a block diagram showing a relevant portion of a personal computer and an extension device according to a first embodiment of the present invention. 
     In FIG. 1, the same elements as those of FIG. 5 are referred to by the same numerals, and a duplicate description thereof will be omitted. 
     An extension device  10  of the first embodiment includes a PCI bus  11  and a video extension device  12  connected to the PCI bus  11 . The video extension device  12  is not provided with a function to calculate coordinates for 3D graphics, and is treated as an old extension device in this example. 
     The extension device  10  further includes a new extension device  13  and a write-enable ROM  14 . The new extension device  13  is connected to the PCI bus  11 , and is provided with a new function to calculate coordinates for 3D graphics. The write-enable ROM  14  stores attribute information of the old extension device, and is accessed by the new extension device  13 . 
     In the extension device  10  of the first embodiment of the present invention, the write-enable ROM  14  stores the attribute information of the video extension device  12 . When the CPU  1  requests the attribute information of the video extension device  12 , the new extension device  13  reads the attribute information of the video extension device  12  from the write-enable ROM  14 , and sends it to the CPU  1  on behalf of the video extension device  12 . 
     In this manner, the extension device  10  of the first embodiment of the present invention includes the video extension device  12  as an old extension device and the new extension device  13  for calculating coordinates for 3D graphics, and, thus, is in possession of old functions of the video extension device  12  and the new function of the new extension device  13 . 
     Since the video extension device  12  can be used without making any modification to its design, development of the extension device  10  involves only the development of the new extension device  13 . This results in the development being completed in a relatively short time period. 
     Further, the extension device  10  of the first embodiment of the present invention is provided with the write-enable ROM  14 . When there is a need to provide another video extension device in place of the video extension device  12 , modifying the attribute information in the write-enable ROM  14  is all that is necessary to cope with the new configuration. Therefore, universal applicability is insured. 
     FIG. 2 is a block diagram showing a relevant portion of a personal computer and an extension device according to a second embodiment of the present invention. 
     In FIG. 2, the same elements as those of FIG. 5 are referred to by the same numerals, and a duplicate description thereof will be omitted. 
     An extension device  20  of the second embodiment includes a PCI bus  21 , a video extension device  22  connected to the PCI bus  21 , and a sound extension device  23  also connected to the PCI bus  21 . The video extension device  22  is not provided with a function to calculate coordinates for 3D graphics, and is treated as an old extension device in this example. The sound extension device  23  does not possess a function to calculate coordinates for 3D sound, and is an old extension device. 
     The extension device  20  further includes a new extension device  24  and a write-enable ROM  25 . The new extension device  24  is connected to the PCI bus  21 , and is provided with a new function to calculate coordinates for 3D graphics and a new function to calculate coordinates for 3D sound. The write-enable ROM  25  stores attribute information of the old extension devices, and is accessed by the new extension device  24 . 
     In the extension device  20  of the second embodiment of the present invention, the write-enable ROM  25  stores the attribute information of the video extension device  22  and the attribute information of the sound extension device  23 . 
     When the CPU  1  requests the attribute information of the video extension device  22  or the attribute information of the sound extension device  23 , the new extension device  24  reads the attribute information of the video extension device  22  or the attribute information of the sound extension device  23  from the write-enable ROM  25 , and sends it to the CPU  1  on behalf of the video extension device  22  or the sound extension device  23 . 
     In this manner, the extension device  20  of the second embodiment of the present invention includes the video extension device  22  and the sound extension device  23  as old extension devices, and further includes the new extension device  24  for calculating coordinates for 3D graphics and 3D sounds, and, thus, is in possession of old functions of the video extension device  22  and the sound extension device  23  as well as the new functions of the new extension device  24 . 
     Since the video extension device  22  and the sound extension device  23  can be used without making any modification to their designs, development of the extension device  20  involves only the development of the new extension device  24 . This results in the development being completed in a relatively short time period. 
     Further, the extension device  20  of the second embodiment of the present invention is provided with the write-enable ROM  25 . When there is a need to provide another video extension device in place of the video extension device  22  or to provide another sound extension device in place of the sound extension device  23 , modifying the attribute information in the write-enable ROM  25  is all that is necessary to cope with the new configuration. Therefore, universal applicability is insured. 
     FIG. 3 is a block diagram showing a relevant portion of a personal computer and an extension device according to a third embodiment of the present invention. 
     In FIG. 3, the same elements as those of FIG. 5 are referred to by the same numerals, and a duplicate description thereof will be omitted. 
     An extension device  30  of the third embodiment includes a PCI bus  31  and a video extension device  32  connected to the PCI bus  31 . The video extension device  32  is not provided with a function to calculate coordinates for 3D graphics, and is treated as an old extension device in this example. The extension device  30  further includes a new extension device  33 . The new extension device  33  is connected to the PCI bus  31 , and is provided with a new function to calculate coordinates for 3D graphics. 
     When the CPU  1  requests the attribute information of the video extension device  32 , the new extension device  33  issues a request for the attribute information to the video extension device  32  on behalf of the CPU  1 . The new extension device  33  then receives the attribute information from the video extension device  32 , and sends it to the CPU  1  on behalf of the video extension device  32 . 
     In this manner, the extension device  30  of the third embodiment of the present invention includes the video extension device  32  as an old extension device and the new extension device  33  for calculating coordinates for 3D graphics, and, thus, is in possession of old functions of the video extension device  32  and the new function of the new extension device  33 . 
     Since the video extension device  32  can be used without making any modification to its design, development of the extension device  30  involves only the development of the new extension device  33 . This results in the development being completed in a relatively short time period. 
     Further, the new extension device  33  issues a request for attribute information to the video extension device  32  when the CPU  1  requests the attribute information of the video extension device  32 , and receives the attribute information from the video extension device  32  to send it to the CPU  1  on behalf of the video extension device  32 . Because of this configuration, even when another video extension device having different attribute information is provided in place of the video extension device  32 , no design change is necessary in the circuit of the new extension device. Therefore, universal applicability is insured. 
     FIG. 4 is a block diagram showing a relevant portion of a personal computer and an extension device according to a fourth embodiment of the present invention. 
     FIG. 4, the same elements as those of FIG. 5 are referred to by the same numerals, and a duplicate description thereof will be omitted. 
     An extension device  40  of the fourth embodiment includes a PCI bus  41 , a video extension device  42  connected to the PCI bus  41 , and a sound extension device  43  also connected to the PCI bus  41 . The video extension device  42  is not provided with a function to calculate coordinates for 3D graphics, and is treated as an old extension device in this example. The sound extension device  43  does not possess a function to calculate coordinates for 3D sound, and is an old extension device. 
     The extension device  40  further includes a new extension device  44 . The new extension device  44  is provided with a new function to calculate coordinates for 3D graphics and a new function to calculate coordinates for 3D sound. 
     When the CPU  1  requests the attribute information of the video extension device  42  or the attribute information of the sound extension device  43 , the new extension device  44  issues a request for the attribute information to the video extension device  42  or the sound extension device  43  on behalf of the CPU  1 . The new extension device  44  then receives the attribute information from the video extension device  42  or the sound extension device  43 , and sends it to the CPU  1  on behalf of the video extension device  42  or the sound extension device  43 . 
     In this manner, the extension device  40  of the fourth embodiment of the present invention includes the video extension device  42  and the sound extension device  43  as old extension devices as well as the new extension device  44  for calculating coordinates for 3D graphics and 3D sound, and, thus, is in possession of old functions of the video extension device  42  and the sound extension device  43  and the new functions of the new extension device  44 . 
     Since the video extension device  42  and the sound extension device  43  can be used without making any modification to their designs, development of the extension device  40  involves only the development of the new extension device  44 . This results in the development being completed in a relatively short time period. 
     Further, the new extension device  44  issues a request for attribute information to the video extension device  42  or to the sound extension device  43  on behalf of the CPU  1  when the CPU  1  requests the attribute information of the video extension device  42  or the attribute information of the sound extension device  43 , and receives the attribute information from the video extension device  42  or the sound extension device  43  to send it to the CPU  1  on behalf of the video extension device  42  or the sound extension device  43 . Because of this configuration, even when another video or sound extension device having different attribute information is provided in place of the video extension device  42  or the sound extension device  43 , no design change is necessary in the circuit of the new extension device. Therefore, universal applicability is insured. 
     Further, the present invention is not limited to these embodiments, but various variations and modifications may be made without departing from the scope of the present invention. 
     The present application is based on Japanese priority application No. 10-129356 filed on May 13, 1998, with the Japanese Patent Office, the entire contents of which are hereby incorporated by reference.