Abstract:
The invention provides a time-division switch and a time-division switching method by which a multi-frame signal of an arbitrary bit length can be outputted to or inputted from an arbitrary time slot. The time-division switching method is applied to weitchably connect time slots between different highways in time-division multiplex communication. The switch includes an external memory to which data from input time slots may be dropped, and from which data may be inserted into output time slots. Fixed data such as tone data may also be inserted into time slots. Dropping and insertion may be performed to replace existing time slot data or to fill new time slots.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a time-division switch and a time-division switching method for a time-division switch. 
     2. Description of the Related Art 
     Conventionally, a time-division switch merely has a basic function to arrange time slots of a data highway inputted thereto arbitrarily on time slots on another highway to be outputted to interconnect different apparatus, which are physically connected to each other outside the time-division switch, with such time slots so that data or an audio signal may be communicated between the different apparatus. 
     Meanwhile, such functions as sending out a tone signal of a busy-back tone, or the like or sending out or receiving a multi-frame signal must all rely upon externally connected apparatus for exclusive use. 
     Consequently, it cannot be avoided that the system is discretized and exhibits a large scale. 
     As described above, a conventional time-division switch requires use of external apparatus for exclusive use for almost all required functions other than the switching function of time slots. 
     For example, the PIAFS (PHS Internal Access Forum Standard), which is a data transfer protocol of the PHS (Personal Handyphone System), can be compared to a 640-bit multi-frame signal train. If it is tried to use the PIAFS protocol for processing of a plurality of lines, then a time-division switch for line separation for distinguishing an audio signal and data from each other, a function of producing multi-frames of 640 bits specified by the PIAFS and inserting the multi-frames into suitable time slots and another function of dropping a multi-frame signal train and extracting a data train of 640 bits from the multi-frame signal train are required. 
     More particularly, for communication of an audio signal, only switch connection is required. However, for communication of data, connection to an apparatus for exclusive use is required even for a call of a same time slot as in the case of the data transfer protocol described hereinabove because contents of the signal are different, and the apparatus for exclusive use must have functions different from mere switch connection such as functions of extracting a multi-frame signal train of 640 bits mentioned hereinabove, performing protocol control specified by the PIAFS based on the signal train and securing the normality of the data. 
     Further, as the number of lines increases, also the numbers of required apparatus for exclusive use increase, which increases the scale of the system. 
     Furthermore, if also such apparatus as an apparatus for sending out guidance information such as a busy-back tone mentioned hereinabove are included, also the number of types of apparatus for exclusive use increases, and as the number of service functions of the system increases, also the number of apparatus for exclusive use is inclined to increase while they are discretized for different functions. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a time-division switching method which allows a time-division switch to have several functions which are conventionally achieved by different apparatus for exclusive use. 
     It is another object of the present invention to provide a time-division switch which achieves several functions which are conventionally achieved by different apparatus for exclusive use. 
     Where principal basic functions required by such apparatus for exclusive use as described above are examined, it is considered that, for a tone signal, data of a time slot of any highway repetitively appear with a certain periodicity. This also applies to an audio guidance. Meanwhile, in the PIAFS protocol described above, multi-frames of 640 bits repetitively appear. Thus, generally speaking, basic functions of almost all apparatus for exclusive use can be included in signal processing of multi-frames having a certain periodicity. 
     Taking notice of the foregoing, the present invention provides a method wherein a time-division switch is provided with, in addition to a switching function wherein time slots of an arbitrary highway inputted are transferred and placed into time slots of another arbitrary highway to be outputted, a reading/writing function for an external memory and the external memory is controlled as an imaginary time slot, thereby providing data insertion and data dropping functions. The time-division switch further has a controlling method wherein read and write addresses of the external memory are circulated so that apparatus for exclusive use in the prior art can be replaced with imaginary time slots to realize economization and miniaturization. 
     In particular, in order to attain the objects described above, according to an aspect of the present invention, there is provided a time-division switching method for switchably connecting time slots between different highways in time-division multiplex communication, comprising the steps of temporarily storing time slots on any of the highways for each time slot, designating time slots on any of the highways and designating phase conversion arrangement, producing an additional new time slot, calculating external memory read address designation bits for reading out data from an external memory from a head address, an end address and an address counter, performing at least one of updating insertion wherein setting data read out in accordance with the external memory read address designation bits is inserted into a pertaining time slot to update the time slot and new insertion wherein the setting data is inserted into the new time slot, and dropping data from the temporarily stored time slots of the highway in accordance with data drop designation bits and storing the dropped data into the external memory in accordance with the external memory storage address designation bits. 
     According to another aspect of the present invention, there is provided a time-division switch with an inserter and a dropper of an external memory added type for switchably connecting time slots between different highways in time-division multiplex communication, comprising a time slot memory for temporarily storing time slots on any of the highways for each time slot, phase conversion arrangement means for designating time slots on any of the highways and designating phase conversion arrangement, additional time slot production means for producing an additional new time slot, address calculation means for calculating external memory read address designation bits for reading out data from an external memory from a head address, an end address and an address counter, insertion means for performing at least one of updating insertion wherein setting data read out in accordance with the external memory read address designation bits is inserted into a pertaining time slot to update the time slot and new insertion wherein the setting data is inserted into the new time slot, and dropping means for dropping data from the temporarily stored time slots of the highway in accordance with data drop designation bits and storing the dropped data into the external memory in accordance with the external memory storage address designation bits. 
     In the time-division switching method and the time-division switch, external data read out in accordance with the external memory read address designation bits may be temporarily stored into an external data storage memory. 
     The time slot to be newly inserted may be a time slot of a multi-frame of a signal train of a number of bits equal to an integral number of times a number of bits which compose a time slot. 
     The setting data to be inserted may be a tone signal. 
     With the time-division switching method and the time-division switch, three address factor storage areas for a head address, an end address and an address count are provided for each time slot, and circulating designation of address is possible for each time slot. Consequently, the time-division switch can perform supervision or sending out of a multi-frame signal for all time slots and can also perform an ordinary switching function. Accordingly, not only communication of audio data, but also transfer of data having a nature of a multi-frame signal train as specified in the PIAFS can be performed collectively by a single LSI without using an external apparatus for exclusive use. Consequently, the time-division switch can perform communication of both of data and an audio signal and can be implemented in such a small size and low power consumption that it can be well applied to a system construction for mobile computing and so forth. 
     The above and other objects, features and advantages of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of a time-division switch with an inserter and a dropper of the external memory added type to which the present invention is applied; and 
     FIG. 2 is a flow chart illustrating a time-division switching method according to the present invention which is applied to the time-division switch of FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring first to FIG. 1, there is shown a time-division switch with an inserter and a dropper of the external memory added type. The time-division switch shown includes time slot memories (TSW)  100  and  101  each for temporarily storing time slots on a highway for each time slot, external data storage memory (SD)  102  for storing data read out from an external memory (MEM)  600 , switch control memories (SC 0 )  400  and  401  for storing designation bits for designating n input highways  200  to  20   n  and time slots of them and n output highways  300  to  30   n  and time slots of them, respectively, a setting data memory (SID)  103  for producing fixed data on an arbitrary time slot, a head address memory (ADR)  104 , an end address memory (END)  106  and an address counter memory (CNT)  105  for controlling the external memory  600 , an address calculator (CAL)  500  for referring to the head address memory (ADR)  104 , end address memory (END)  106  and address counter memory (CNT)  105  to calculate an address, a control interface section (INF)  700 , and an input/output path control section (ACOUNT)  800 . 
     Each of the switch control memories (SC 0 )  400  and  401  has a designation bit storage region provided therein so as to allow designation of a time slot of any highway or designation of setting data of the setting data memory (SID)  103 , and designation bits are stored into the designation bit storage regions of the switch control memories (SC 0 )  400  and  401 , thereby providing a data insertion function to the time-division switch. 
     The setting data memory (SID)  103  not only allows setting of arbitrary data but also has provided therein a designation bit storage region for designating a storage destination of drop data from a slot of an arbitrary highway, and designation bits are stored into the designation bit storage region of the setting data memory (SID)  103 , thereby providing a data dropping function to the time-division switch. Also, address designation bits for cumulatively storing the thus dropped data into the external memory (MEM)  600  are stored into the designation bit storage region of the setting data memory (SID)  103 . 
     It is to be noted that the setting data memory (SID)  103 , head address memory (ADR)  104 , end address memory (END)  106  and address counter memory (CNT)  105  have memory areas corresponding to respective addresses thereof. 
     The setting data memory (SID)  103  has a pattern wherein setting data are held as they are and another pattern wherein external memory address designation bits for serially reading out storage data of the external memory (MEM)  600  based on a result of address calculation of the address calculator (CAL)  500  to re-write and update data of a designated time slot. 
     Meanwhile, in the switch control memories (SC 0 )  400  and  401 , designation bits are set so that data of the external memory (MEM)  600  may be selected with the external memory address designation bits. 
     Consequently, the time-division switch has a function of outputting stored contents of the external memory (MEM)  600  to a time slot of an arbitrary highway and allows transmission and reception of a multi-frame signal train mentioned hereinabove through the external memory (MEM)  600 . 
     The control interface section (INF)  700  writes designation conditions mentioned hereinabove into the switch control memories (SC 0 )  400  and  401  from a control apparatus such as an external CPU. 
     The input/output path control section (ACOUNT)  800  controls addresses, data and input and output lines to the functional blocks which form the time-division switch. Further, the input/output path control section (ACOUNT)  800  controls an output selector (OUTSEL)  900  or  901  in accordance with designation bits stored in the switch control memory (SC 0 )  400  or  401  to insert data set in the setting data memory (SID)  103  into an arbitrary time slot in one of the n output highways  300  to  30   n.    
     The external data storage memory (SD)  102  stores data written through the control interface section (INF)  700  or data read out from the external memory (MEM)  600  based on a result of address calculation of the address calculator (CAL)  500 . 
     The setting data memory (SID)  103  has a pattern wherein setting data are held as they are as described hereinabove, and another pattern wherein designation bits which designate writing into the external memory (MEM)  600  from which a result of address calculation of the address calculator (CAL)  500  from the address counter memory (CNT)  105  is derived. The latter designation bit pattern provides a data dropping function wherein data dropped from the time slot memories (TSW)  100  and  101  are successiely stored into successively designated addresses of the external memory (MEM)  600 . 
     As described hereinabove, in order to process a multi-frame signal, the setting data memory (SID)  103  has a region in which circulation designation data is stored so that a result of address calculation for designating a storage region of the external memory (MEM)  600  may have a circulation property. If such circulation designation data is stored in the just-mentioned region of the setting data memory (SID)  103 , then circulating addresses are produced making use of the three address factors of the head address memory (ADR)  104 , end address memory (END)  106  and address counter memory (CNT)  105 . 
     Now, operation of the time-division switch is described with reference to FIG.  2 . 
     First, phase conversion arrays of time slots and drop and insertion designation bits are stored into the switch control memories (SC 0 )  400  and  401  (step  21 ). When time slots are stored into the time slot memories (TSW)  100  and  101 , a central control system (CP)  1000  sequentially reads the switch control memories (SC 0 )  400  and  401  and discriminates whether mere phase conversion, insertion or drop should be performed (step  22 ). If only phase conversion is to be performed, the central control system (CP)  1000  phase converts data from the input side time slots into output side time slots in accordance with the designation bits of the switch control memories (SC 0 )  400  and  401 . 
     When insertion should be performed, the central control system (CP)  1000  discriminates from the designation bits which one of the setting data pattern and the external memory data read pattern should be performed (step  25 ). If the external memory data read pattern should be performed, then the central control system (CP)  1000  reads out data from the external memory (MEM)  600  in accordance with the designation bits stored in the setting data memory (SID)  103  and stores the data into the external data storage memory (SD)  102  (step  26 ) and inserts the data into a new time slot. 
     On the other hand, if the setting data pattern should be performed (step  24 ), then the central control system (CP)  1000  additionally places a new frame (step  24 ). Then, the central control system (CP)  1000  reads out stored insertion data (step  28 ) from the setting data memory (SID)  103  and inserts the data into a time slot of the new frame. 
     When dropping should be performed (step  22 ), the central control system (CP)  1000  designates the storage destination of drop data in accordance with the designation bits of the setting data memory (SID)  103  (step  30 ) and stores the drop data into the designated address of the external memory (MEM)  600 . 
     While a preferred embodiment of the present invention has been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.