Peripherals of computer

1. A peripheral for notifying a USB-connected upper apparatus of a device descriptor and allowing said upper apparatus to specify a communication partner destination on the basis of function information shown in said device descriptor, comprising:

a peripheral function information holding unit which holds function information indicative of functions of said peripheral;

a dependent peripheral function information holding unit which holds function information indicative of functions of a dependent peripheral which is USB-connected; and

a USB control unit which reads out either the function information held in said peripheral function information holding unit or the function information held in said dependent peripheral function information holding unit on the basis of a selecting instruction and notifies said upper apparatus of the device descriptor in which the read-out function information is shown.

2. The peripheral according to claim 1 , wherein

when said peripheral is an image reading apparatus and said dependent peripheral is an image forming apparatus,

said peripheral function information holding unit holds the function information indicative of an image reading function, and

said dependent peripheral function information holding unit holds the function information indicative of an image forming function.

3. The peripheral according to claim 2 , wherein said USB control unit has a multi-device descriptor forming unit which forms the device descriptor in which the function information which is read out by said selecting instruction is shown.

4. The peripheral according to claim 3 , further comprising an original reading unit which reads an original, and

wherein when it is detected that the original has been arranged, said original reading unit notifies said USB control unit of an original detection signal as said selecting instruction, and

when said original detection signal is received, said USB control unit reads out the function information indicative of the image reading function.

5. The peripheral according to claim 4 , further comprising a timer which notifies said USB control unit of a left-original detection signal as said selecting instruction when it is detected that said original has been arranged and left, and

wherein when said left-original detection signal is received, said USB control unit reads out the function information indicative of the image forming function.

6. The peripheral according to claim 4 , wherein

said original reading unit reads out the arranged original and, when it is detected that there are no originals to be read, notifies said USB control unit of an end detection signal as said selecting instruction, and

when said end detection signal is received, said USB control unit reads out the function information indicative of the image forming function.

7. The peripheral according to claim 3 , further comprising a specific information extracting unit which analyzes a control command from said upper apparatus and extracts specific information, and

wherein when said specific information is a command described by a control language of an image reading apparatus, said specific information extracting unit notifies said USB control unit of said command as said selecting instruction, and

when said command is received, said USB control unit reads out the function information indicative of the image reading function.

8. The peripheral according to claim 7 , wherein when information showing that a process based on said command has been finished is received as said selecting instruction, on the basis of said command, said USB control unit reads out the other function information which is not read out.

9. The peripheral according to claim 3 , further comprising a specific information extracting unit which analyzes a control command from said upper apparatus and extracts specific information, and

wherein when said specific information is a command described by a control language of an image forming apparatus, said specific information extracting unit notifies said USB control unit of said command as said selecting instruction, and

when said command is received, said USB control unit reads out the function information indicative of the image forming function.

10. The peripheral according to claim 9 , wherein when information showing that a process based on said command has been finished is received as said selecting instruction, on the basis of said command, said USB control unit reads out the other function information which is not read out.

11. The peripheral according to claim 1 , wherein

when said peripheral is an image forming apparatus and said dependent peripheral is an image reading apparatus,

said peripheral function information holding unit holds the function information indicative of an image forming function, and

said dependent peripheral function information holding unit holds the function information indicative of an image reading function.

12. The peripheral according to claim 11 , wherein said USB control unit has a multi-device descriptor forming unit which forms the device descriptor in which the function information which is read out by said selecting instruction is shown.

13. The peripheral according to claim 12 , further comprising an original reading unit which reads an original, and

wherein when it is detected that the original has been arranged, said original reading unit notifies said USB control unit of an original detection signal as said selecting instruction, and

when said original detection signal is received, said USB control unit reads out the function information indicative of the image reading function.

14. The peripheral according to claim 12 , further comprising a specific information extracting unit which analyzes a control command from said upper apparatus and extracts specific information, and

wherein when said specific information is a command described by a control language of an image reading apparatus, said specific information extracting unit notifies said USB control unit of said command as said selecting instruction, and

when said command is received, said USB control unit reads out the function information indicative of the image reading function.

15. The peripheral according to claim 12 , further comprising a specific information extracting unit which analyzes a control command from said upper apparatus and extracts specific information, and

wherein when said specific information is a command described by a control language of an image forming apparatus, said specific information extracting unit notifies said USB control unit of said command as said selecting instruction, and

when said command is received, said USB control unit reads out the function information indicative of the image forming function.

16. The peripheral according to claim 1 , further comprising an operation panel which receives said selecting instruction, and

wherein when said selecting instruction is received by said operation panel, said USB control unit executes bus resetting in the USB-connection with said upper apparatus before the notification of said device descriptor.

17. The peripheral according to claim 1 , further comprising a specific information extracting unit which analyzes a control command from said upper apparatus and extracts specific information, and

wherein when an instruction to execute bus resetting in the USB-connection with said upper apparatus is shown in said extracted specific information, said USB control unit executes said bus resetting.

18. The peripheral according to claim 1 , wherein the USB-connection with said upper apparatus is hot plug-in connection, bus resetting in said USB-connection is executed by the hot plug-in connection.

19. A peripheral for notifying a USB-connected upper apparatus of a device descriptor and allowing said upper apparatus to specify a communication partner destination on the basis of function information shown in said device descriptor, comprising:

a peripheral function information holding unit which holds function information indicative of functions of said peripheral;

a dependent peripheral function information holding unit which holds function information indicative of functions of a dependent peripheral which is USB-connected; and

a USB control unit which reads out either the function information held in said peripheral function information holding unit or the function information held in said dependent peripheral function information holding unit on the basis of a selecting instruction and notifies said upper apparatus of the device descriptor in which the read-out function information is contained,

wherein said USB control unit has a host control section which executes a relay for communicating between said upper apparatus and said dependent peripheral, when said dependent peripheral is specified as said communication partner destination by said upper apparatus.

20. The peripheral according to claim 19 , wherein said peripheral is a scanner; said dependent peripheral is a printer.