Patent Publication Number: US-2004054493-A1

Title: Device for recovering connection

Description:
FIELD OF THE INVENTION  
       [0001] The present invention relates to a connection recovery unit and, more particularly, to a connection recovery unit which performs a connection recovery control of the equipment connected to a bus capable of connecting personal computers, peripheral equipment thereof, or audio/video equipment (referred to as AV equipment hereafter), such as in a network using a high-speed serial bus, IEEE1394 (“IEEE Standard for a High Performance Serial Bus” defined in IEEE Std.1994-1995).  
       BACKGROUND OF THE INVENTION  
       [0002] In recent years, the diffusion rate of personal computers to the general household is increased, and a variety of techniques for raising the utilization factor thereof for the general users are developed. In addition, it is general to process image and voice, for example, as digital data, and accordingly, it is generally conducted in a household to process the data of the digital video camera by using a personal computer. In she circumstances as described above, USB (universal serial bus) and IEEE1394 are devised as techniques for improving the connectivity of the computer with peripheral equipment, such as printer and image scanner, and some of those are now in practical use.  
       [0003] In contrast to the USB which requires an intervening computer for connecting the peripheral equipment, IEEE1394 does not require the presence of such a computer for the connection, and thus is capable of transferring main signals and control signals between the audio equipment such as the digital video camera and the audio equipment as well as connecting the personal computer with the peripheral equipment such as printer, hard disk, or image scanner. This means that a network can be configured by connecting together a plurality of equipment each adapted to IEEE1394 (referred to as “1394 equipment” hereinafter), and thus IEEE1394 is considered as a promising standard to be used for a household LAN (local area network).  
       [0004]FIG. 4 exemplifies a network of AV equipment, or  1394  equipment, configured by using an IEEE1394 bus. In the example shown in FIG. 4, five AV equipment, or 1394 equipment,  80   a  to  80   e  are connected to the IEEE1394 bus B 10 . In order to associate the AV equipment with the isochronous channels during transferring data between the AV equipment, each AV equipment is provided with a master plug register (MPR) and a plug control register (PCR) defined in IEC61883 standard (“Consumer Audio/Video equipment-Digital interface-Part 1: General”, Reference number CEI/IEC 61883-1:1998).  
       [0005] These registers include input registers and output registers for inputting/outputting the audio data and video data, wherein the master plug registers include input master plug registers (iMPR) and output master plug registers (oMPR), and the plug control registers include input plug control registers (iPCR) and output plug control registers (oPCR).  
       [0006] In the example shown in FIG. 4, AV equipment  80   a  to  80   d  are provided with iMPRs  82   a  to  82   d,  respectively, whereas AV equipment  80   e  is provided with an oMPR  84 . iMPR  82   a  to iMPR  82   d  are provided with iPCRs  86  and  88 , iPCR  90 , iPCR  92 , and iPCRs  94  and  96 , respectively, whereas oMPR  84  is provided with oPCR  98 . In FIG. 4, C 10  denotes the isochronous channels. When an isochronous transfer is performed between the AV equipment connected to the IEEE1394 bus B 10 , the isochronous channel C 10  is established for effecting the data transfer.  
       [0007]FIG. 5 shows the detailed formats of the registers, wherein (a) shows the format of the output master plug register (oMPR), (b) shows the format of the input master plug register (iMPR), (c) shows the format of the output plug control register (oPCR), and (d) shows the format of the input plug control register (iPCR). These formats are defined by standard. It is to be noted that the number given to the bottom of each format in the drawing expresses the number of bits of each data constituting the format.  
       [0008] A single oMPR  84  or a single iMPR  82   a  to  82   d  is provided in each of the AV equipment  80   a  to  80   e,  and manages the number of oPCRs  98  and iPCRs  86  to  96  in the AV equipment. The number of each of oPCRs and iPCRs to be provided in a single AV equipment is  31  at the maximum. There are provided, in the oPCRs and iPCRs, fields FC 2  and FD 2 , respectively, for storing the information representing the presence or absence of the broadcasting connection, fields FC 3  and FD 3 , respectively, for storing the information representing the number of point-to-point connections, and fields FC 5  and FD 5 , respectively, for storing the information representing the isochronous channel number, wherein all the information is needed for establishing the connection. In addition, there are also provided, in the oPCR, a field FC 6  storing the information representing the transfer rate of the isochronous data flow and a field FC 8  for storing the information representing the band thereof. The register address wherein MPR and PCR are described is described from FFFFF00900 h  address to FFFFF009FF h  address (h represents the hexadecimal notation) in the address space CSR (Command and Status Register) defined in IEEE1394 standard.  
       [0009] By suitably setting these PCRs, the isochronous data output from the AV equipment can set up the path of the isochronous data flow between the AV equipment, whereby the data transfer can be effected between arbitrary AV equipment. Connections using the PCRs will be described hereinafter, again with reference to FIG. 4.  
       [0010] The connections using PCRs are categorized in two types including point-to-point connection and a broadcasting connection.  
       [0011] The point-to-point connection is such that one of oPCRs of an AV equipment is connected to one of iPCRs of another AV equipment via an isochronous channel. For example, in FIG. 4, the data between oPCR  98  of AV equipment  80   e  and iPCR  90  of AV equipment  80   b  corresponds this type. This connection is associated with a protection so that only the equipment or the control application which established the connection can exclusively rewrite the register.  
       [0012] In addition, a plurality of point-to-point connections can exist in a single PCR. In the example shown in FIG. 4, for example, this applies to the connection between oPCR  98  of AV equipment  80   e  and iPCR  94  of AV equipment  80   d.  In this case, as illustrated in the drawing, three point-to-point connections exist using the same isochronous data flow.  
       [0013] The broadcasting connection includes two connections: a broadcasting-out connection wherein an oPCR of an AV equipment is connected to a single isochronous channel; and a broadcasting-in connection wherein one of iPCRs of another AV equipment is connected to the single isochronous channel.  
       [0014] For example, the connection between oPCR  98  of AV equipment  80   e  and the broadcasting channel number (usually set at “63”) of the isochronous data corresponds to the broadcasting-out connection, whereas the connection between iPCR  92  in AV equipment  80   c  and the broadcasting channel number of the isochronous data corresponds to the broadcasting-in connection.  
       [0015] In the two types of the broadcasting connection, the connection for the broadcaster and the connection for the audience are set independently of each other, or without depending on the state of each other. In addition, any equipment or control application, which does not established the broadcasting connection, can rewrite the PCR and cut-off the connection, and also can deprive the broadcasting isochronous channel of the equipment then transmitting.  
       [0016] The start of the data transmission and reception, after the connection is established between the AV equipment, can be effected by controlling the transmitting-side AV equipment and the receiving-side AV equipment by using an AV/C (audio video control) command (AV/C Digital Interface Command Set version 3.0, 1394 Trade Association, Apr. 15, 1998, or “AV/C Tape Recorder/Player Subunit Specification version 2.”, 1394 Trade Association, Jan. 11, 1998). In the AV/C command, commands such as reproduction, stop, rapid feed, back-wind, picture recording, pause and slowdown are available. The transmission/reception of the AV/C command on the  1394  bus is effected by using the function control protocol defined in IEC61883 standard. For ending the isochronous transmission, the settings of the PCRs of the transmitting/receiving AV equipment are cancelled for breaking the connection.  
       [0017] In the connections using the PCRs as described above, insertion or removal of the AV equipment, for example, causes occurrence of a bus reset for initialization of the bus, and the PCRs are also initialized at the same time. This once involves cancellation of all the connections which are then established in the bus. The procedure for recovering the cancelled connections to the initial state before the bus reset is prescribed in IEC61883-1. In IEC61883-1, the attribution of the connection is prescribed, as in the case of the point-to-point connection being protected for the equipment (or application) that established the connection.  
       [0018] However, any right is not prescribed for the AV equipment, for which the connection is established, to control the equipment by using the AV/C command. JP Patent Application 11-215972 describes to which equipment (or application) the right for performing the control using the AV/C command should be assigned, in relation to the AV equipment for which the connection is established.  
       [0019] The summary of the technique described therein is such that a controller stores the order of the connection which the controller itself established, and shares the stored information with other controllers, wherein one of the plurality of controllers sharing the connection therebetween is assigned the right for controlling the AV equipment. The practical procedure for determining the controlling right is such that one of the controllers which first established the connection is basically assigned the controlling right and one of the controllers storing a lowest value in the counter counting the point-to-point connection of the PCR among the controllers storing such information.  
       [0020] By using the techniques as described above, it is possible to establish or cancel the connections between the AV equipment, determine the controlling right for the AV equipment, and recover the cancelled connections. If a bus reset occurs and subsequently the cancelled connection is to be recovered, there are some problems as described hereinafter. In the procedure prescribed in IEC61883-1 for recovering the cancelled connections, the order of the connection recovery is not prescribed for the case where a plurality of point-to-point connections are superposed.  
       [0021] Accordingly, the plurality of controllers that established the superposed connections may operate for re-establishment in disorder and independently of each other by using the occurrence of the bus reset as a trigger. As for the assignment of the controlling right, if the controlling right is to be assigned to one of the controllers which first established the connection in accordance with the teaching of Patent Application 11-215972, there arises a problem such that if the order of the superposition is changed between the states before and after the bus reset, the right for controlling the AV equipment is changed accordingly.  
       [0022] The above problem is more specifically described hereinafter. FIG. 6 shows an example of the connections established in the network formed by AV equipment (1394 equipment) before occurrence of the bus reset. In the example shown in FIG. 6, three controllers  100   a  to  100   c  are connected to the IEEE1394 bus B 12 , and in addition, six 1394 equipment  102   a  to  102   f  are connected thereto. It is assumed here that 1394 equipment  102   a  operates as a transmitter, whereas 1394 equipment  102   d  to  102   f  operate as receivers.  
       [0023] It is also assumed that a point-to-point connection C 20  is established between 1394 equipment  102   a  and 1394 equipment  102   d,  a point-to-point connection C 22  is established between 1394 equipment  102   a  and 1394 equipment  102   e,  and a point-to-point connection C 24  is established between 1394 equipment  102   a  and 1394 equipment  102   f,  whereby three connections are superposed on 1394 equipment  102   a.    
       [0024] It is also assumed that the point-to-point connection C 20  is established by a controller  100   a,  the point-to-point connection C 22  is established by a controller  100   c,  and the point-to-point connection C 24  is established by a controller  100   b,  and that the order C 20 , C 22  and C 24  as recited herein is the order of the establishment of the connections. If the control as to the assignment of the controlling right is such that the controller which first established the connection is assigned the right for controlling the 1394 equipment, then the right for controlling 1394 equipment  102   a  on which three connections are superposed is assigned to controller  100   a  which first established the point-to-point connection C 20 .  
       [0025] In the circumstance of connections as described above, a case is considered wherein a bus reset occurred and three controllers  100   a  to  100   c  recovered the connections. Since each of controllers  100   a  to  100   c  recovered only the connection which the each controller itself established, the order of the connections established by three controllers  100   a  to  100   c  may be changed. FIG. 7 shows an example of the connections established after the bus reset occurred in the network formed by the AV equipment (1394 equipment).  
       [0026] After the recovery, it is assumed that, as shown in FIG. 7, connection C 30  is first established by controller  100   c,  connection C 32  is then established by controller  100   b,  and connection C 34  is lastly established by controller  100   a.  In this case, since controllers  100   a  to  100   c  recover the respective connections independently of each other or without any association, the right for controlling 1394 equipment  102   a  is assigned to controller  100   c.    
       [0027] As described above in connection with the conventional technique, since the state shown in FIG. 6 wherein the connections are superposed in the order of C 20 , C 22  and C 24  before the bus reset is shifted to the state shown in FIG. 7 wherein the connections are superposed in the order of C 30 , C 32  and C 34  after the bus reset, the right for controlling 1394 equipment  102  is deprived of controller  100   a  by controller  100   c  after the bus reset.  
       SUMMARY OF THE INVENTION  
       [0028] The present invention is conceived based on the circumstances as described above, and it is an object of the present invention to provide a connection recovery unit which is capable of re-establishing the connections after the bus reset in the order of the connections established before the bus reset, in the case where the connections cancelled by the bus reset are recovered on the bus, such as a 1394 bus, which is capable of serial and bi-directional packet communication and connecting a plurality of AV equipment together.  
       [0029] A first aspect of the connection recovery unit according to the present invention is directed to a connection controller connected onto a bus, which is capable of serial and bi-directional packet communication and connecting a plurality of equipment together, the connection controller including: a connection information storage member for storing a logical connection status of the equipment connected to the bus; and a determination member for determining priority order of a logical connection status of the equipment connected to the bus based on the logical connection status stored in the connection information storage member and a logical connection status stored in the other equipment connected to the bus, when the bus communicates initializing information thereto.  
       [0030] A connection recovery unit according to the first aspect features that the connection information storage member stores information of data-transmitting-side equipment and information of data-receiving-side equipment in pair as the logical connection information.  
       [0031] A connection recovery unit according to the first aspect features that the connection information storage member stores information for discriminating transmitting-side equipment and receiving-side equipment, information of input or output of the equipment and information of number of one-to-one connections.  
       [0032] A connection recovery unit according to the first aspect features that the logical connection information represents at least the number of one-to-one connections.  
       [0033] A connection recovery unit according to the first aspect features that the bus is compliant with IEEE1394 bus.  
       [0034] A second aspect of the connection recovery unit according to the present invention is directed to a connection recovery unit connected to a bus compliant with IEEE1394 bus for controlling connections of a plurality of equipment connected to the bus, the connection recovery unit includes: a plug control register controller for controlling packet transmission/reception via the bus, controlling plug control registers in other equipment, and generating information representing connections between the equipment via the bus; a connection information storage member for storing a connection status generated by the plug control register controller; and a connection re-establishment controller for receiving information stored in the connection information storage member and information as to the plug control register in other equipment connected onto the bus when a bus reset is communicated from the bus, determining information for controlling the connection timings between the equipment and the plug control register in the other equipment, and communicating these information to the plug control register controller.  
       [0035] A connection recovery unit according to the second aspect of the present invention features that the connection information storage member stores the information of the output plug control register constituting the one-to-one connection information and information of the input plug control register in a pair.  
       [0036] The connection information storage member may feature that it includes a field for representing the output or input plug control register, a field for representing an order number of the plug control register provided in the equipment, a field for representing the value of the on-to-one connection information of the plug control register, and a subject-node ID field for representing the node ID of the equipment in which the plug control register is provided.  
       [0037] In addition, the connection information storage member may feature that it is disposed in a control status register space prescribed in IEEE1212.  
       [0038] According to the present invention, since the connection status (connection order) before the initialization is stored after the initialization even when the bus is initialized due to the communication of the initializing information from the bus, the connections can be re-established after the initialization in accordance with the connection order established before the initialization.  
       [0039] More specifically, the present invention resides in that the connections are re-established in accordance with the connection order established before the bus reset, in the case of performing connection recovery after the bus reset. For achieving this operation, in the preferred embodiment of the present invention, among the contents set in the plug control register, the value of the number of point-to-point connections (referred to as PPC value hereinafter) is stored. During the connection recovery, the connections are re-established when the PPC value of the plug control register of the equipment desired to be set therein equals the PPC value stored in the controller minus one.  
       [0040] If the PPC value of the plug control register of the equipment which is desired to be set during the connection recovery does not become equal to the PPC value stored in the controller minus one due to the cut-off of the controller, absence of operation of the controller which has a priority for the connection re-establishment or so, then the re-establishment is performed by reducing one from the stored value after a specified time length elapsed.  
       [0041] By using the methods as described above, connection re-establishment is achieved in accordance with the connection order established before the bus reset.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0042]FIG. 1 is a block diagram showing the connection recovery unit according to an embodiment of the present invention.  
     [0043]FIG. 2 is a point-to-point connection information table s stored in the connection information storage member  24 .  
     [0044]FIG. 3 is a flowchart showing operation of the connection re-establishment controller  26  provided in the connection recovery unit according to the embodiment of the present invention includes.  
     [0045]FIG. 4 shows an example of the network of 1394 equipment, or AV equipment, configured by using an IEEE1394 bus.  
     [0046]FIG. 5 is a diagram showing the detailed formats of the registers.  
     [0047]FIG. 6 shows an example of connections established before occurrence of a bus reset in the network configured by AV equipment (1394 equipment).  
     [0048]FIG. 7 shows an example of the connections established after the occurrence of the bus reset in the network configured by AV equipment (1394 equipment). 
    
    
     BEST MODE OF THE INVENTION  
     [0049] Hereinafter, with reference to the drawings, a connection controller according to an embodiment of the present invention will be described in detail.  
     [0050]FIG. 1 is a block diagram showing the connection recovery unit according to the embodiment of the present invention. In the example illustrated in FIG. 1, the present invention is applied to a 1394 bus. In FIG. 1, the connection recovery unit  10  according to the embodiment of the present embodiment is roughly comprised of a connection recovery controller  20  and a 1394 bus interface  30 . The connection recovery controller  20  is comprised of a plug control register controller (PCR controller)  22 , a connection information storage member  24 , and a connection reestablishment controller  26 .  
     [0051] The PCR controller  22  performs establishment and cut-off of the connections based on information of the point-to-point connections between the AV equipment which are connected onto the 1394 buses, and performs programming of PCR of the AV equipment via the 1394 bus interface  30 . The PCR controller  22  stores the contents of the setting of the PCR of the AV equipment in the connection information storage member  24 , after the point-to-point connection is established. The stored contents stored in the connection information storage member  24  are referred to as a point-to-point connection information table, hereinafter. FIG. 2 shows the point-to-point connection information table stored in the connection information storage member  24 .  
     [0052] In order to set the oPCR and iPCR in pair upon performing a point-to-point connection, the information of both the oPCR and iPCR is stored in pair after the point-to-point connection is established. The pair of information of the oPCR and iPCR is herein referred to as P2P information pair. The detailed contents of a P2P information pair will be described with reference to FIG. 2. It is to be noted that the description with reference to FIG. 2 is conducted assuming that the connection recovery unit  10  of the embodiment of the present invention shown in FIG. 1 is provided in each of the controllers  100   a  to  100   c  shown in FIGS. 6 and 7; (a) shows the point-to-point connection information table stored in the connection information storage member  24  of controller  100   a , (b) shows the point-to-point connection information table stored in the connection information storage member  24  of controller  100   b,  and (c) shows the point-to-point connection information table stored in the connection information storage member  24  of controller  100   c . In this case, the physical IDs of 1394 equipment and the controllers in FIG. 6 and FIG. 7 are such as follows: the physical ID of 1394 equipment  102   a  is “0”, the physical ID of 1394 equipment  102   b  is “1”, the physical ID of 1394 equipment  102   c  is “2”, the physical ID of 1394 equipment  102   d  is “3”, the physical ID of 1394 equipment  102   e  is “4”, the physical ID of 1394 equipment  102   f  is “5”, the physical ID of controller  100   a  is “6”, the physical ID of controller  100   b  is “7”, and the physical ID of controller  100   c  is “8”.  
     [0053] The fields F 1  in tables (a) to (c) of FIG. 2 represent whether the PCR is an iPCR or an oPCR, wherein “0” is stored for representing an oPCR and “1” is stored for representing an iPCR. The PCR number mounted on the AV equipment is stored in the field F 2 . The number of point-to-point connections of the PCR is stored in the field F 3 . It is to be noted that the value stored in this field F 3  is referred to as the PPC value hereinafter. A bus ID which represents the most significant ten bits of ID of the subject node, i.e., the AV equipment for which the PCR controller  22  has set the PCR, and a physical ID which represents the least significant six bits thereof are stored in the fields F 4  and F 5 , respectively.  
     [0054] In the example shown in (a) of FIG. 2, the P2P information pair is a record R 10  including a record R 1  and record R 2 . In the example shown in (b) of FIG. 2, the P2P information pair is a record R 12  including a record R 5  and record R 6 . In the example shown in (c) of FIG. 2, the P2P information pair is a record R 13  including a record R 7  and record R 8 .  
     [0055] More specifically, with reference to FIG. 2, the value in field F 1  of the record R 1  is “0”, the value in the field F 3  is “1”, the bus ID in the field F 4  is “1023”, and the physical ID in the field F 5  is “0”. In the record R 1 , since the value in the field F 1  is “0”, such a record specifies an AV equipment for transmitting data. That is, the contents of record R 1  indicates that the AV equipment transmitting the data is an AV equipment having a physical ID of “0” and connected to the bus having a bus ID of “1023”, and the number of point-to-point connections thereof is “1”.  
     [0056] Since the value in the field F 1  of the record R 2  which forms a pair together with the record R 1  is “1”, the record R 2  specifies an AV equipment receiving the data. That is, based on the contents of the record R 2 , the AV equipment receiving the data is an AV equipment having a physical ID of “3” and connected to the bus having a bus ID of “1023”, and the number of point-to-point connections thereof is “1”. The point-to-point connection information table shown in (a) of FIG. 2, which is stored in controller  100   a  shown in FIG. 6, for example, shows that controller  100   a  storing therein the P2P information pair in the record R 10  shown in (a) of FIG. 2 established a single point-to-point connection wherein the AV equipment having a physical ID of “0” transmits the data to the AV equipment having a physical ID of “3”. In this way, i.e., by storing the point-to-point connection information table wherein oPCR and iPCR are paired, the connections between the AV equipment can be stored in the connection information storage member  24 .  
     [0057] The connection re-establishment controller  26 , after receiving a bus reset notification via the 1394 bus interface  30 , receives the information stored in the connection information storage member  24 , and also receives the PCR information of the equipment which is related to this information via the 1394 bus interface  30 . The connection re-establishment controller  26  then determines, based on these information, the timing of connections between the equipment and information for controlling the PCRs of the other equipment, and notifies the PCR controller  22  of the information. The PCR controller  22 , after receiving the connection information, recovers the point-to-point connection via the 1394 bus interface  30  without delay.  
     [0058] Operation of the connection recovery unit according to the embodiment of the present invention and having the configuration described above will now be described. FIG. 3 is a flowchart showing operation of the connection re-establishment controller  26  provided in the connection recovery unit of the embodiment of the present invention. After start of the operation, processing is conducted for determining the order of extraction for the P2P information pairs stored in the connection information storage member  24  (step S 10 ). In this processing, the P2P information pairs in the point-to-point connection information tables are sorted based on the ascending order of the PPC values of oPCR in each pair. It is to be noted that the order of P2P information pairs is not considered if the PPC values therefor are equal.  
     [0059] After the order of extraction for the P2P information is determined, processing is conducted for the extraction of the P2P information pairs (step S 11 ). In this processing, the “P2P information pairs” are read from the point-to-point connection information in the order of arrangement thereof, i.e., in the ascending order of the PPC values. Each time one of the P2P information pairs is read out, the PPC value of oPCR in the P2P information pair thus extracted in step S 11  is stored in the variable m, and at the same time, the PPC value of iPCR in the P2P information pair thus extracted in step S 11  is stored in the variable n (step S 12 ). Here, the variables m and n are such for storing integers equal to or above zero.  
     [0060] After the above procedure is finished, in the processing of steps S 20  and S 40 , the value of PCR of the subject node is compared against the contents of the variables “m” and “n” stored in the processing of step S 12 , for examining whether the situation allows recovery of the point-to-point connections. In these steps, the value of oPCR of the subject node is compared against the value of variable “m” in the step S 20 , whereas the value of iPCR of the subject node is compared against the value of variable “n” in step S 40 . The subject node is obtained from the subject node ID in the P2P information pair. It is a matter of course that the subject node is determined by comparing the node IDs before and after the bus reset, if the node ID of the subject node is changed due to the bus reset.  
     [0061] The processing of step S 20  will be detailed hereinafter. Upon start of the processing of step S 20 , an initialization of loop variable “i” is first conducted to set the value of the loop variable “i” at “0” (step S 21 ). Subsequently, oPCR of the subject node is read out (step S 22 ). Thereafter, it is judged whether or not the PPC value of the oPCR read out in the processing of step S 22  is equal to the value m−1 (step S 23 ).  
     [0062] If the judgement in the processing of step S 23  indicates an inequality, i.e, if the result of judgement in step S 23  is “NO”, then the process advances to step S 24 . In step S 24 , processing for incrementing the loop variable “i”, i.e., processing for adding “1” to the loop variable “1” is conducted. Thereafter, it is judged whether or not the value of the loop variable “i” is equal to or above “3” (step S 25 ), and if the loop variable “i” is less than “3” then the process advances to step S 26 , followed by waiting for a time length of “T” and subsequently returning to the processing of step S 22 .  
     [0063] On the other hand, if it is judged in the processing of step S 25  that the value of the loop variable “i” is equal to or above “3”, i.e., if the result of the judgement in step S 25  is “YES”, then the process advances to step S 30 . In step S 30 , processing is conducted for the case wherein the PPC value of oPCR of the subject node does not become equal to m−1 after waiting a specified time length (2T in this example). More specifically, the value of the variable “m” is decremented, i.e., decreased by one in step S 31 , letting the decremented value to be a new value of “m”. Then, it is judged whether or not the value of the updated variable “m” is equal to or above “1”, returning to the processing of step  21  if the value is equal to or above “1”, whereas advancing to the processing of step S 62  if the value is less than “1”.  
     [0064] If it is judged in step S 23  as described above that the PPC value of oPCR read out in the processing of step  22  is equal to the value of m- 1 , i.e., the result of judgment in step S 24  is “YES”, then the process advances to step S 41 , wherein the value of loop variable “i” is initialized to be set at “0”. Subsequently, iPCR of the subject node is read out (step S 42 ), and it is judged whether or not the PPC value of iPCR read out in the processing of step S 42  is equal to the value of n−1 (step S 43 ).  
     [0065] If it is judged in the processing of step S 43  that both are not equal, i.e., if the result of judgement in step S 43  is “NO”, then the process advances to step S 44 . In step S 44 , the processing is such that the loop variable “i” is incremented, i.e., the loop variable “i” is added by one. Subsequently, it is judged whether or not the value of loop variable “i” is equal to or above “3” (step S 45 ), and the process advances to step S 46  if the loop variable “i” is less than “3”, waiting for a specified time length “T” to return to the processing of step S 42 .  
     [0066] On the other hand, if it is judged in the processing of step S 45  that the value of loop variable “i” is equal to or above 3, i.e., if the result of judgement in step S 45  is “YES”, then the process advances to step S 50 . In step S 50 , similarly to step S 30 , processing is conducted for the case wherein the PPC value of iPCR of the subject node does not become equal to n−1 after waiting a specified time length (2T in this example). More specifically, the value of variable “n” is decremented, i.e., reduced by one in step S 51 , letting the decremented value to be a new value of “n”. It is judged whether the value of the updated variable “n” is equal to or above “1”, returning to step S 41  if the value is equal to or above “1”, whereas advancing to the processing of step S 62  if the value is less than “1”. In step S 62 , the process is ended while displaying a fail in the re-establishment of point-to-point connections.  
     [0067] If it is judged in step S 43  as described above that the PPC value of iPCR read in the processing of step S 42  is equal to the value of n−1, i.e., the result of judgement in step S 43  is “YES”, then the process advances to step S 61 , wherein a point-to-point connection is established between oPCR and iPCR of the subject node. After the point-to-point connection is established, it is judged whether or not all the P2P information pairs in the point-to-point connection information are processed (step S 63 ). If the processing is not completed, i.e., the result of judgement in step S 63  is “NO”, then the process returns to step S 11 , wherein a next point-to-point connection is subjected to re-establishment processing. On the other hand, if it is judged in step S 63  that the processing for all the P2P information pairs is completed, i.e., if the result of judgment is “YES”, then the process for re-establishment of the point-to-point connections is ended.  
     [0068] Although an embodiment of the present invention is described heretofore, the present invention is not limited to the above embodiment, and may be changed for design thereof within the scope of the present invention. For example, although the present invention is exemplified by the case wherein the present invention is applied to the IEEE1394 standard, the present invention can be applied to any connection controller so long as the connection controller is connected to a bus which performs a serial and bi-directional packet transmission and can connect a plurality of AV equipment together.