Abstract:
A common package serves as, for example, a common network interface package for a switching system. Since the common package is usable for various purposes, its cost is reduced and the cost of maintenance and management of the switching system is reduced. The common package is a printed board package ( 35 ) installed in an apparatus and used for a variety of purposes. The common package includes a programmable device ( 36 ), memories ( 45  to  48 ) for storing programs to configure the programmable device, a selector ( 41 ) for selecting one of the programs from the memory so that the selected program may so configure the programmable device as to make the common package serve as a specific circuit, and an instruction unit ( 51 ) for issuing an instruction to specify the program to be selected by the selector.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a common package, and particularly, to a common network interface package applicable to a switching system. 
     2. Description of the Related Art 
     A switching system generally consists of four kinds of apparatuses, i.e., 1) apparatuses for making connections between subscribers, between trunks, or between subscribers and trunks, 2) channel apparatuses for receiving subscriber lines and trunk units and controlling and testing channels, 3) central processing apparatuses for analyzing data entering the switching system and issuing instructions to the channel apparatuses and I/O apparatuses, and 4) the I/O apparatuses for sending and receiving data to and from the central processing apparatuses. 
     FIG. 1 shows a conventional switching system. 
     Subscriber terminals  11  are connected to subscriber lines, which are received by subscriber circuits (SLCs)  12  of the switching system. Signals from the subscriber circuits  12  are multiplexed by subscriber concentrators (SLCCs) incorporated in a network interface (NW-INF 1 )  13 . More precisely, the network interface  13  converts signals from subscribers into time slots in highway signals. 
     The highway signals are multiplexed by a network unit (NW)  14  into a higher highway signal, which is transferred to a switch (SW)  19 . A line processor (LPR)  15  processes scan data (SCN) indicating the ON/OFF-hook states of subscriber terminals and signal data (SD) from higher devices. For local connections, the line processor  15  carries out switching operations within the network unit  14 . The line processor  15  also controls and tests channels. 
     Signals from trunk circuits (TRKS)  16  are multiplexed by trunk concentrators (ATCs) incorporated in a network interface (NW-INF 2 )  17 . More precisely, the network interface  17  converts trunk signals into time slots in highway signals, which are multiplexed by a network unit (NW)  18  into a higher highway signal. The higher highway signal is transferred to the switch  19 . 
     According to instructions from a central processing apparatus (CC)  20 , the switch  19  exchanges time slots in higher highway signals and realizes connections among the subscribers and trunks through the network units  14  and.  18 . An I/O apparatus  21  sends and receives data for system management and maintenance to and from the central processing apparatus  20 . 
     FIGS. 2A and 2B show the structures of a time slot and highway signal transferred between the network interface  13  and the network unit  14 . 
     The time slot (TS) of FIG. 2A is for voice data and consists of eight bits, and the highway signal of FIG. 2B consists of 8-bit time slots and includes housekeeping data and SD/SCN (signal data/scan) data. 
     In FIG. 2B, a frame of the highway signal has a frequency of 8 KHz (a period of 125 μs) containing 128 time slots TS 0  to TS 127 . The time slots TS 0  to TS 3  carry the housekeeping data containing maintenance and management data. The time slots TS 64  to TS 67  carry the SD/SCN data. 
     Each frame contains housekeeping data of 32 bits (=8 bits×4 time slots) and SD/SCN data of 32 bits. In this example, 16 frames form a multiframe having a period of 2 ms (125 μs×16), and data is updated multiframe by multiframe. 
     The network interfaces  13  and  17  are connected to the network units  14  and  18  and control the discrete circuits  12  and  16  arranged under the network interfaces  13  and  17 . The network interfaces  13  and  17  achieve different functions, and therefore, are composed of different packages. 
     Each network interface has a shelf on which network interface packages are installed to control the discrete circuits such as the subscriber circuits  12  and trunk circuits  16 . These packages are designed exclusively for the discrete circuits, and therefore, have the following problems: 
     (1) Too Many Kinds of Packages 
     On the one hand, the network interface packages have each a common interface with respect to the network units  14  and  18 . For example, the subscriber concentrators in the network interface  13  and the trunk concentrators in the network interface  17  have each a common interface with respect to the network units  14  and  18 . 
     On the other hand, the packages have different interfaces or LSIs optimized for the subscriber circuits  12  or trunk circuits  16 . This is because back wiring boards (BWBs) arranged on the shelves of the network interfaces  13  and  17  for the packages differ from one to another depending on the circuits  12  and  16 . 
     Recent development in multimedia communication has increased the number of discrete circuits. To cope with this, a variety of network interface packages must be prepared. This results in increasing the production, maintenance, and management costs of the packages. 
     (2) Problems in Highway Interfacing of Packages 
     A highway signal transferred between the network interface  13  ( 17 ) and the network unit  14  ( 18 ) employs a format that contains both voice data and control data such as SD/SCN. This format restricts the quantity of the control data to a minimum in the predetermined time slots as shown in FIG.  2 B. 
     Recent development in multimedia communication has produced a variety of control data and has increased the quantity thereof, and these expanding pieces of control data are hardly handled with information provided by the predetermined time slots in the highway signal. 
     The conventional technique of arranging voice data and control data in the same highway signal is inefficient. For example, one must execute a program each time to monitor every frame in each multiframe of the highway signal at intervals of 125 μs to see if packages have been installed on or removed from a shelf. This deteriorates the overall efficiency of the switching system. 
     The control data contained in the highway signal is a mixture of different functions. Namely, pieces of the control data are disorderly arranged in the highway signal, and therefore, are inefficiently processed by a microprocessor or software for switching work. This deteriorates the overall efficiency of the switching system. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a network interface package to be installed on a shelf of a network interface, having a common structure for lower circuit blocks and a general structure for a network unit, to help reduce the kinds of network interface packages and decrease the production, maintenance, and management costs thereof. 
     In order to accomplish the object, a first aspect of the present invention provides a common package installed in an apparatus and configurable to serve as a selected one of specific circuits. The common package consists of a programmable device, a memory for storing programs to configure the programmable device, a selector for selecting one of the programs from the memory so that the selected program may so configure the programmable device as to make the common package serve as a specific circuit, and an instruction unit for issuing an instruction to specify the program to be selected by the selector. 
     A second aspect of the present invention provides a common package installed in an apparatus and configurable to serve as a selected one of specific circuits. The common package consists of a programmable device to be so configured according to a program as to make the common package serve as a specific circuit, a memory for storing the program, an instruction unit for specifying the program, a notify unit for notifying the apparatus of the specified program, and a control unit for receiving the specified program from the apparatus and storing the same in the memory. 
     The programmable device of any one of the first and second aspects may be an FPGA (field programmable gate array). The memory of the first aspect may consist of nonvolatile memories for storing FPGA controlling programs, respectively. The memory of the second aspect may be a volatile memory. 
     The instruction unit issues the instruction according to self inventory data provided by a BWB (back wiring board) of the apparatus, or data provided by a manual setting unit installed on the common package. The common package is connected to discrete circuit packages. 
     The common package may have an interface circuit that includes lines for separately transmitting a data signal and a control signal. Data carried by the control signal is divided into zones each containing similar data. 
     The arrangements of the present invention may be combined in various ways. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be more clearly understood from the description as set forth below with reference to the accompanying drawings, in which: 
     FIG. 1 shows a switching system according to a prior art; 
     FIG. 2A shows an example of a time slot handled by the system of FIG. 1; 
     FIG. 2B shows an example of a highway signal handled by the system of FIG. 1; 
     FIG. 3 shows a common network interface package according to a first embodiment of the present invention; 
     FIG. 4 shows a common network interface package according to a modification of the first embodiment; 
     FIGS. 5A and 5B show back-wiring-board self inventory data and meanings thereof; 
     FIG. 6 is a flowchart showing an FPGA configuring flow according to the first embodiment; 
     FIG. 7 shows a common network interface package according to another modification of the first embodiment; 
     FIG. 8 shows a common network interface package according to still another modification of the first embodiment; 
     FIG. 9 shows a common network interface package according to a second embodiment of the present invention; 
     FIG. 10 is a flowchart showing an FPGA configuring flow according to the second embodiment; 
     FIG. 11 shows an example of an interface circuit incorporated in the package of the present invention; 
     FIGS. 12A to  12 C show an example of SD/SCN data in a highway signal according to the present invention; 
     FIG. 13 shows a switching system employing the packages of the present invention; and 
     FIG. 14 shows a multiplexing/demultiplexing package. according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 3 shows a common network interface package (NW-INF)  35  according to the first embodiment of the present invention. 
     The common package  35  is connected to discrete circuit packages  31  to  34 . The discrete circuit packages include a subscriber circuit package (SLC)  31 , a trunk circuit package (TRK)  32 , a receiver circuit package (REC)  33 , and a signal control circuit package (SGC)  34 . 
     The common package  35  has the following four elements: 
     1) Programmable Device  36   
     The programmable device  36  is configured so that the common package  35  may properly serve for the discrete circuit packages connected thereto. In this example, the programmable device  36  is an FPGA (field programmable gate array), which may be of a FLEX type of ALTERA (registered trade name). 
     2) Memory 
     The memory stores programs to configure the FPGA  36  so that the common package  35  may properly serve for the discrete circuit packages connected thereto. In this example, the memory is composed of ROMs  45  to  48  that store programs appropriate for the discrete circuit packages connected to the common package  35 . 
     3) Selector (SEL)  44   
     The selector  44  selects one of the programs from the ROMs  45  to  48  that is appropriate for the discrete circuit packages connected to the common package  35  and transfers the selected program to the FPGA  36 . 
     4) Interface circuit 
     The interface circuit interfaces the FPGA  36  with a network unit  54  and provides the selector  44  with a select signal to select one of the programs from the ROMs  45  to  48  according to externally provided data. In this example, the interface circuit is an exclusive interface LSI (INF-LSI)  49 . 
     A back wiring board (BWB)  52  provides the common package  35  with self inventory data (SI)  53 , which is made of a level signal to indicate the type and version of the back wiring board  52  of a shelf on which the common package  35  is installed. The network unit  54  corresponds to the network unit  14  or  18  of FIG.  1 . 
     The FPGA  36  consists of a configurable circuit (CIR)  37  to be configured for the discrete circuit packages controlled by the common package  35 , an interface  38  interfacing with the interface LSI  49 , and a download controller  39  for downloading a program from a selected one of the ROMs  45  to  48 . 
     The interface LSI  49  consists of an interface  50  for transferring voice data and SD/SCN data to and from the network unit  54 , and a selection controller  51  for decoding the self inventory data  53  from the back wiring board  52 , providing a ROM select signal accordingly, and controlling the configuration of the FPGA  35 . 
     FIG. 4 shows a common network interface package  35  according to a modification of the first embodiment. No discrete packages  31  to  34  of FIG. 3 are connected to the common package of FIG.  4 . The other parts of FIG. 4 are the same as those of FIG.  3 . An FPGA  36  in the common package of FIG. 4 is configured to provide a required function. 
     FIGS. 5A and 5B show examples of the self inventory data  53  provided by the back wiring board  52 . FIG. 6 shows a flow of configuring the FPGA  36  of FIG.  3 . 
     Configuring the common package  35  for the discrete circuit packages connected thereto will be explained with reference to FIGS. 5A,  5 B, and  6 . 
     The common package  35  is installed on a shelf and is turned on. Step S 10  checks to see if the interface LSI  49  is normally operating. In steps S 11  and S 12 , the interface LSI  49  receives the self inventory data  53  from the back wiring board  52 . Steps S 13  and S 14  determines discrete circuit packages for which the common package  35  serves according to the self inventory data  53  and provides the selector  44  with a ROM select signal  43  to select one of the ROMs  45  to  48 . 
     FIG. 5A shows an example of the self inventory data  53 . 
     In-the example, the self inventory data  53  is a 4-bit level signal made of bits D 3  to D 0 . FIG. 5B shows examples of the meanings of combinations of the bits D 3  to D 0 . Although discrete circuit packages including a subscriber circuit package (SLC), a trunk circuit package (TRK), and a receiver circuit package (REC) shown in FIG. 5B are represented with different levels of the bits D 3  to D 0 , they may have the same levels in the bits D 3  to D 0  when they have each the same interface with respect to the common package  35 . 
     In steps S 15  and S 16 , the interface LSI  49  sends a ROM configuration signal  42  to the download controller  39 . In steps S 17  and S 18 , the download controller  39  sends a configuration request  41  to the selected ROM, which provides a program to configure the configurable circuit  37  and interface  38 . Step S 19  operates the common package  35  for the discrete circuit packages connected thereto. 
     In this way, the common package  35  of FIG. 3 is usable for any one of the discrete circuit packages  31  to  34  irrespective of the functions of the discrete circuit packages by selecting a proper one of the ROMs  45  to  48  according to the self inventory data  53 . 
     FIGS. 7 and 8 show common network interface packages according to modifications of the first embodiment. 
     In FIG. 7, the common package  35  has no selector  44  of FIG.  3  and employs only one ROM  55 . A select signal from a selection controller  51  is supplied to a higher address of the ROM  55  to switch a program page to another in the ROM  55 . Each program page of the ROM  55  contains a program for a discrete circuit package, and therefore, the flow of FIG. 6 is applicable to the common package  35  of FIG.  7 . 
     In FIG. 8, the common package  35  employs no self inventory data from a back wiring board. Instead, the common package  35  has a DIP switch  56  that is manually operated to set a function for the common package  35 . 
     Although the DIP switch  56  involves a risk of miss setting due to manual operation, the common package  35  of FIG. 8 is more versatile because it is installable on any shelf. The DIP switch  56  may also be used for an interface  50  contained in an interface LSI  49  so that the interface  50  may provide a required interface function. 
     FIG. 9 shows a common network interface package according to a second embodiment of the present invention, and FIG. 10 is a flowchart showing an FPGA configuring flow according to the second embodiment. 
     The second embodiment employs a volatile RAM  57  instead of ROMs. In steps S 20  to S 22 , an interface LSI  49  receives self inventory data  53  from a back wiring board  52 . These steps are the same as steps S 10  to S 12  of FIG.  6 . 
     Step S 23  determines a configuration to form according to the self inventory data  53  and notifies a higher device such as a central processing unit of the determination through a notification unit  60 . In response to the notification, the higher device returns corresponding configuration data  58 . In steps S 24  and S 25 , a download controller  59  receives the configuration data and stores it in the RAM  57 . The following steps S 26  to S 29  are the same as steps S 16  to S 19  of FIG.  6 . 
     The second embodiment configures an FPGA  36  of the common package  35  according to configuration data provided by a higher device. This improves the versatility of the common package  35 . In addition, the second embodiment is capable of externally updating and debugging the common package  35  and configuration data. The second embodiment may employ the DIP switch of FIG.  8 . 
     FIG. 11 shows an example of the interface  50  incorporated in the interface LSI  49  of any one of the embodiments of the present invention. 
     To expand the versatility of the common package  35  with respect to the network unit  54 , the present invention completely divides the conventional highway structure (FIG. 2B) into voice data handled by a highway interface  61  and control data such as SD/SCN handled by a highway interface  62 . This arrangement is capable of coping with a future increase in data transmission speed and data capacity. 
     The highway interface  62  for SD/SCN data employs a zone method. For this purpose, the highway interface  62  has a zone divider  63  to optimize data units to be processed and accessed, as shown in FIGS. 12A to  12 C. 
     FIGS. 12A to  12 C show an example of SD/SCN data in a highway signal according to the present invention. 
     In FIG. 12A, the present invention employs a multiframe period of 2 ms that is compatible with the prior art. Each word time slot (WTS) is composed of 32 bits to match with CPU processing. One multiframe contains 1024 time slots to secure eight times as large data transmission capacity as that of the prior art. 
     In FIG. 12B, eight zones  0  to  7  are cyclically assigned to a series of time slots. Each zone involves similar control data such as data about fault, or each zone is related to a given function. 
     The zone method has the advantages of reducing monitoring points because similar data such as fault data is collected in one zone and of improving switching performance because it is possible to shorten read intervals of significant bits or zones. For example, the monitoring of removal of packages (32 packages) can be done by collectively monitoring 32 bits in a word time slot  800 . The zone method improves the versatility of control data including SD/SCN data and realizes a common interface to reduce load on firm software and improve the performance thereof. 
     FIG. 13 shows a switching system employing the common packages of the present invention. 
     The system includes an analog subscriber circuit block (SLC)  71 , a digital subscriber circuit block (DLC)  72 , an analog trunk circuit block (AT)  73 , and a PB signal receiver circuit block (REC)  74 . These circuit blocks have each a common interface on the network interface side, and therefore, are connected to a concentrator package (LTSH)  78  that is one of the common packages of the present invention. 
     In this embodiment, a piece of self inventory data provided by a back wiring board is made of 16 bits, and a single piece of the self inventory data is sufficient for the concentrator package  78  to control the discrete circuit packages  71  to  74  because the packages  71  to  74  have each the same interface. A three-party conversation trunk package  77 , which is another one of the common packages of the present invention, has no discrete packages thereunder and is connected to a network unit  85 . The package  77  corresponds to the package of FIG.  4 . 
     A multiplexing/demultiplexing package  79 , which is another one of the common packages of the present invention, is connected to a signal control package  75 . 
     FIG. 14 shows an example of the multiplexing/demultiplexing package  79 . A dotted area  36  is an FGPA, and a dotted area  49  is an interface LSI on the network side. The package  79  multiplexes voice and control highways coming from the signal control package  75  into a voice highway and an SD/SCN highway. 
     The other blocks of the switching system of FIG. 13 are not directly related to the present invention, and therefore, only their names will be stated. They are a digital circuit trunk  84 , a highway switch  86 , a tone generator  87 , a path control circuit  88 , bus arbiters  76  and  89 , and a central processing unit  90 . 
     The network interface packages  77  to  79  of the present invention easily recognize a shelf on which the packages are installed according to the self inventory data provided by the back wiring board. Interfaces  81  to  83  on the network unit  85  side are standardized. Accordingly, the common packages  77  to  79  that are hatched in FIG. 13 are of the type that is installable on any shelf. 
     In summary, the present invention provides the following effects: 
     The common network interface package of the present invention incorporates a programmable device so that the package is configurable for various downstream circuits. This reduces the cost of the package itself and that of a switching system that employs the common package. The present invention reduces the number of packages to be stocked and mistakes occurring when installing packages on a shelf of the switching system, thereby making the maintenance of the switching system easier. 
     The present invention forms a switching system with common packages of a single kind, thereby reducing designing, manufacturing, and testing processes and facilities. The common package of the present invention is capable of easily coping with an increase in the number of discrete circuit packages connected thereto. 
     The present invention employs the versatile signal structure that allows an increase in the number of bits in SD/SCN data and divides the data into zones each containing similar data. 
     The signal structure with the zone technique is applicable to the common packages and is capable of coping with the addition and removal of data bits. The zone technique is advantageous in monitoring and improving the performance of firm software. 
     Due to these effects, a switching system employing the present invention is functional, reliable, and inexpensive. 
     The present invention is applicable not only to network interface packages but also to any other packages installed in general apparatuses.