JP2008278160A - Non-hit switching circuit and its common staff generation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-hit switching circuit capable of performing a non-hit path switching by using common staff information in a SDH (Synchronous Digital Hierarchy) transmitter, and to provide its common staff generation method. <P>SOLUTION: The non-hit switching circuit 10 receives data sent out through at least two transmission lines 12 and 14, pointer interpretation parts 20 and 22 respectively take out received staff information 110 and 112 from the two pieces of received data, and a staff detection part 30 detects staff information in common to the route of the two pieces of received data by counting the received staff information 110 and 112. Thus, the staff detection part 30 is achieved by a simple circuit configuration and the circuit scale is reduced. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an uninterruptible switching circuit that generates common stuff information necessary for memory read control in order to switch an uninterrupted path for data received from at least two transmission lines in an SDH transmission apparatus, and an It is about the common staff generation method.

  Conventionally, an SDH (Synchronous Digital Hierarchy) transmission device inserts MF information for identifying a frame phase into a path overhead (POH: Path OverHead) before sending data to two transmission lines, and further sends the data. The necessary processing is applied. This necessary processing includes, for example, AU pointer insertion processing in the pointer generation processing unit, section overhead (SOH: Section OverHead) insertion in the transmission processing unit, as defined in ITU-T recommendation G.707, There are scramble processing and electrical / optical conversion processing.

  On the other hand, the SDH transmission apparatus receives SDH frame data sent from another transmission apparatus via two transmission paths, and switches the path, that is, the path of these reception data in this apparatus, Select a path. In this SDH transmission apparatus, each received data is processed separately. For example, as specified in ITU-T recommendation G.707, the reception processing unit performs optical / electrical conversion processing, timing extraction, descrambling processing. And SOH termination is applied.

  In addition, the SDH transmission apparatus identifies the position of the beginning (J1 byte) of the virtual container (VC) path based on the AU pointer value of the received data in the pointer interpretation unit, and determines the VC path from each of the two received data. Are separated. In the SDH transmission apparatus, when the frequency of the VC paths is asynchronous, the frequency offset of these VC paths is adjusted using negative or positive stuff bytes. The pointer interpreter can separate VC paths by identifying such stuff bytes.

  Further, in the SDH transmission apparatus, a multi-frame (MF) detection unit determines the frame phase of each received data of the two transmission paths based on the MF information inserted in the POH, and performs memory write control. Based on these frame phases, the unit generates a write address for writing the two received data to the respective phase absorption memories.

  These phase absorption memories are used to delay the output of one of the data so that the path phase of these received data matches the same phase in order to switch the path of the two received data without interruption. is there. The delay amount for absorbing the phase difference between the two received data is calculated by the phase difference determination unit, and the read phase of the phase absorption memory is determined based on the phase of these received data. Further, based on this read phase, the read control unit generates a read address of the phase absorption memory.

  Also, in the SDH transmission apparatus, the error detection unit detects error information of two transmission paths, and the selection control unit selects a path with no error based on these error information, and performs uninterrupted path switching. The selection signal is generated. Based on this selection signal, the selection unit selects an appropriate path from the two transmission paths.

  For example, the transmission apparatus described in Patent Literature 1 performs transmission switching of the transmission path without interruption as described above.

  Some SDH transmission apparatuses have a staff detection unit in order to perform such uninterrupted switching.

  When the two received data are synchronized, the internal clock frequency of the transmission device and the VC path frequency match, so once the read phase is determined, the delay amount of the phase absorption memory is kept constant. It is.

  However, when the two received data are asynchronous, the difference between the internal clock frequency and the VC path frequency causes a shift between the write phase such as the frame phase of the VC path and the read phase such as the frame phase in the apparatus. As a result, the delay amount of the phase absorption memory increases when the internal clock frequency is low, and decreases when the internal clock frequency is high.

  In order to prevent such a variation in the delay amount of the phase absorption memory, the stuff detection unit compares the write phase and the read phase and monitors the current memory accumulation amount, that is, the delay amount, and this accumulation amount and the line continuity are monitored. If the difference from the initial delay amount exceeds a predetermined threshold, a positive or negative common staff request is transmitted to the read control unit.

  The read control unit changes the read phase from the phase absorption memory by executing a positive or negative common stuff operation in response to the reception of such common stuff, and the amount of accumulation in the phase absorption memory is constant. Can be maintained.

  For example, in the uninterruptible switching transmission system described in Patent Document 2, it is possible to monitor the accumulation amount of the phase absorption memory as described above for each transmission path.

However, if any one of the transmission lines is abnormal, for example, if there is a loss of multi-frame synchronization, the writing operation cannot be performed normally. By generating, the information of the normal route can be used.
JP ll-225095 JP 2002-026855 A

  However, in the non-instantaneous switching circuit of the conventional SDH transmission apparatus, the stuff detection unit is configured so that the non-instantaneous switching can be realized even when the frame phase of the data received from the two transmission paths is asynchronous. Although the write address and the read address are compared and the difference between the calculation result and the initial delay amount is calculated to determine the delay variation amount, the delay amount of the phase absorption memory is kept constant. In such a conventional staff detection unit, it is necessary to mount a complicated comparison operation circuit for each transmission path, and the circuit scale increases.

  It is an object of the present invention to provide an uninterruptible switching circuit and a common stuff generation method that can eliminate such drawbacks of the prior art and efficiently generate common stuff.

  In order to solve the above-described problems, the present invention is connected to at least two transmission lines, receives data transmitted through the transmission line, and passes at least two paths for the at least two data. A non-instantaneous switching circuit that selects and switches one of these at least two paths in an SDH transmission device having a phase absorption memory that temporarily stores these data in order to synchronize and output the phase of these data And the pointer interpretation means for extracting the received stuff information from these data, and by counting the received stuff information, the delay amount of the data of the current frame and the delay amount of the data accumulated in the phase absorption memory A common staff detecting means for detecting a fluctuation amount corresponding to the difference and generating a common staff based on the fluctuation amount. To.

  Further, it is connected to at least two transmission lines, receives data transmitted through the transmission line, and at least two of these at least two data are received by an SDH transmission apparatus having at least two paths. The common stuff generation method for generating a common stuff for selecting and switching one of the two routes is to perform a pointer interpretation process for extracting received stuff information from these data and to output the data in synchronism with each other. The accumulation step for temporarily accumulating these data in the phase absorption memory, and the difference between the delay amount of this data in the current frame and the delay amount of the data accumulated in this phase absorption memory by counting this reception stuff information A common staff detection step for detecting a fluctuation amount corresponding to the fluctuation amount and generating a common staff based on the fluctuation amount. Characterized in that it contains.

  According to the uninterruptible switching circuit of the present invention, the pointer interpreter extracts each received stuff information based on the data received from at least two transmission lines, and the stuff detector counts the received stuff information. By doing so, stuff information common to these transmission paths can be detected, so that the stuff detection unit is realized with a simple circuit configuration, and the circuit scale is reduced.

  In addition, the non-instantaneous switching circuit according to the present invention increases the above effect as the number of paths accommodated by the SDH transmission system, that is, the number of transmission lines connected to the SDH transmission apparatus increases. A transmission device having a large capacity can be more effectively reduced in production cost and power consumption.

  Next, an embodiment of a non-instantaneous switching circuit in an SDH (Synchronous Digital Hierarchy) transmission apparatus according to the present invention will be described in detail with reference to the accompanying drawings. For example, as shown in FIG. 1, the uninterruptible switching circuit 10 receives data transmitted via the two transmission lines 12 and 14 by the reception processing units 16 and 18, and the pointer interpretation units 20 and 22 The reception stuff is extracted based on the received data, the error detection units 24 and 26 detect the error information of the transmission paths 12 and 14, and the selection control unit 28 is instantaneously based on the error information. The stuff detecting unit 30 generates a common stuff according to the reception stuff and the selection signal, and the memory read control unit 32 performs a phase according to the common stuff. The reading phase of the absorption memories 34 and 36 is controlled, and the selection unit 38 selects the path of received data according to this selection signal.

  In this embodiment, the circuit 10 determines the multi-frame phase of the received data by the multi-frame (MF) detection units 40 and 42 in order to write the received data to the phase absorption memories 34 and 36, and stores the data in the memory The write controllers 44 and 46 generate write addresses for the memories 34 and 36 based on these reception phases. Further, in the circuit 10, the phase difference determination unit 48 determines the phase difference of the received multiframe, and the memory read control unit 32 generates a read address based on the phase difference and the common stuff, and the phase absorption memory 34 and Data is selected from the memory on the error-free side of 36. Note that portions not directly related to understanding the present invention are not shown and redundant description is avoided.

  As shown in FIG. 2, for example, the circuit 10 is provided in an SDH transmission device 52, particularly a receiving device thereof. The transmission device 52 is connected to another SDH transmission via at least two transmission lines 12 and 14. Connect to device 54. Although the transmission device 52 can actually be connected to many other SDH transmission devices, only a few other SDH transmission devices 54 are shown in FIG. 2 to avoid complication.

  As shown in FIG. 2, the other SDH transmission device 54 sends SDH frame data to the transmission lines 12 and 14 and sends it to the transmission device 52. The MF insertion unit 56 uses such transmission data. MF information is inserted into the path overhead (POH: Path OverHead) to make the frame phase identifiable, and transmission data 152 and 154 are transmitted toward the transmission lines 12 and 14.

  Such another transmission device 54 performs necessary processing on the transmission data 152 and 154.For example, the pointer generation processing units 58 and 60 and the transmission processing units 62 and 64 are ITU-T Recommendation G. Necessary processing as specified in 707 is performed. The pointer generation processing units 58 and 60 generate AU (Administrative Unit) pointers and insert them into the transmission data 152 and 154. The transmission processing units 62 and 64 insert a section overhead (SOH: Section OverHead) into the transmission data 156 and 158 in which the AU pointer is inserted, and execute a scramble process and an electrical / optical conversion process.

  In the circuit 10 of this embodiment, the reception processing units 16 and 18 receive the SDH frame data from the transmission lines 12 and 14, and perform necessary processing on the received data, for example, optical / electrical conversion processing. , Timing extraction, descrambling processing, and section overhead termination processing, and the received data 102 and 104 after these processing are supplied to the pointer interpretation units 20 and 22.

  The pointer interpretation units 20 and 22 perform pointer termination processing on the received data 102 and 104. For example, as defined in ITU-T recommendation G.707, the received data 102 and 104 are stuff bytes. And the AU pointer is detected, the head position (J1 byte) of the virtual container (VC) path is identified from the AU pointer value, and the VC path is separated based on the head position. Also, these interpretation units 20 and 22 output the received data 106 and 108 after the pointer termination processing and store them in the phase absorption memories 34 and 36.

  In particular, in this embodiment, the pointer interpreters 20 and 22 interpret the received data 102 and 104, identify positive or negative stuff bytes used to adjust the frequency offset, and use such stuff bytes. The reception staffs 110 and 112 based on the above are detected and supplied to the staff detection unit 30.

  The error detection units 24 and 26 detect bit errors occurring in the transmission lines 12 and 14, and in this embodiment, the error detection units 24 and 26 are based on the received data 106 and 108 output from the pointer interpretation units 20 and 22. And 14 error information 114 and 116 are detected.

  Based on the error information 114 and 116 of the transmission lines 12 and 14 detected by the error detection units 24 and 26, the selection control unit 28 generates a selection signal 118 for controlling the uninterrupted path switching, that is, the transmission line 12 And 14, a signal for selecting an appropriate path without error is generated and supplied to the selection unit 38.

  Further, the selection control unit 28 generates the selection signal 120 based on the error information 114 and 116 and supplies the selection signal 120 to the stuff detection unit 30 in the same manner as described above.

  The staff detection unit 30 generates a staff request for changing the read phase of the phase absorption memories 34 and 36, that is, the common staff 122 in response to the reception staffs 110 and 112 and the selection signal 120. The data is supplied to the memory read control unit 32.

  The staff detection unit 30 of the present embodiment is configured to include UP / DOWN counters 72 and 74, threshold value excess determination units 76 and 78, and a staff selection unit 80, for example, as shown in FIG.

  The UP / DOWN counters 72 and 74 update their counters according to the reception staffs 110 and 112 input from the pointer interpretation units 20 and 22 and the common staff 122 fed back from the staff selection unit 80. The counter value varies corresponding to the difference between the delay amount of the received data of the current frame (hereinafter referred to as the current delay amount) and the delay amount of the data accumulated in the phase absorption memory (hereinafter referred to as the accumulated delay amount). The quantities 172 and 174 are supplied to the threshold value excess determination units 76 and 78.

  These counters 72 and 74 update, for example, signed binary counter values. When the reception stuffs 110 and 112 are positive stuff, 1 is added, and when they are negative stuff, 1 is subtracted. Update the counter value. The counters 72 and 74 update the counter value by subtracting 1 when the common staff 122 is positive stuff and adding 1 when the common staff 122 is negative stuff.

  The threshold value excess determining units 76 and 78 have predetermined threshold values set in advance, compare the fluctuation amounts 172 and 174 obtained from the UP / DOWN counters 72 and 74 with the predetermined threshold values, and according to the comparison result Individual staff requests 176 and 178 are provided to staff selection section 80.

  The threshold excess determination units 76 and 78 of the present embodiment output the individual staff requests 176 and 178 when the fluctuation amounts 172 and 174 reach a predetermined threshold, and the counter values 172 of the UP / DOWN counters 72 and 74 are output. The positive staff is output as the individual staff requests 176 and 178 when the positive and negative values are 174, and the negative staff is output when the negative values are negative. For example, when the predetermined threshold value is 1, these determination units 76 and 78 output a positive stuff request when the counter value, which is the fluctuation amount, changes from 0 to 1, and the counter value changes from 0 to −1. Output negative staff request when changed to.

  The staff selection unit 80 selects the individual staff request 176 or 178 from the threshold excess determination unit 76 or 78 as the individual staff request for the transmission line 12 or 14 according to the selection signal 120 from the selection control unit 28, and is common. The data is output as the staff 122 and supplied to the memory read control unit 32. The staff selection unit 80 also feeds back and supplies the common staff 122 to the UP / DOWN counters 72 and 74.

  The memory read control unit 32 controls the timing of reading the transmission data 130 and 132 from the phase absorption memories 34 and 36. In this embodiment, the memory read control unit 32 detects the read phase 128 from the phase difference determination unit 48 and the stuff detection unit 30. The read addresses 124 and 126 for the phase absorption memories 34 and 36 are generated according to the common staff 122 that has been set.

  The memory read control unit 32 uses the read phase 128 to delay the phase of the data to be read from one of the phase absorption memories 34 and 36 so that the phase of the data to be read from the other is the same. Read addresses 124 and 126 are generated.

  The phase absorption memories 34 and 36 temporarily store data received from the transmission paths 12 and 14, and in this embodiment, store the received frame data 106 and 108 from the pointer interpreters 20 and 22.

  In addition, the phase absorption memories 34 and 36 temporarily store the received data 106 and 108 from the transmission lines 12 and 14 in order to match the path phase to the same phase, and delay one of the transmission data 130 or 132 in the same phase. This makes it possible to perform path switching without interruption.

  These phase absorption memories 34 and 36 write the received data 106 and 108 in accordance with the write addresses 134 and 136 supplied from the memory write control units 44 and 46, and the read address 124 supplied from the memory read control unit 32. The transmission data 130 and 132 are read out in accordance with, and 126, and transmitted to the selection unit 38.

  The selection unit 38 selects a path of received data according to the selection signal 118 from the selection control unit 28, and outputs the transmission data 130 or 132 from the phase absorption memory 34 or 36 as output data 138.

  MF detectors 40 and 42 detect the MF information inserted in the POH of received data 106 and 108, determine the MF phases 140 and 142 of received data 106 and 108 based on the MF information, and perform memory write control Supply to parts 44 and 46.

  Based on the MF phases 140 and 142, the memory write controllers 44 and 46 generate a write address for writing the received data 106 and 108 to the phase absorption memory 34 or 36. In addition, the memory write control units 44 and 46, based on the MF phases 140 and 142, write the received data 106 and 108 obtained via the transmission lines 12 and 14 to the phase absorption memory 34 or 36. 144 and 146 are obtained and supplied to the phase difference determination unit 48.

  The phase difference determination unit 48 inputs the path phases 144 and 146 from the memory write control units 44 and 46, and determines the read phase of the phase absorption memory 34 or 36 based on these path phases 144 and 146. In this embodiment, the phase difference between the received data 106 and 108 is determined, and the read phase 128 is determined by calculating the delay amount of the timing for reading the transmission data 106 or 108 from the memory 34 or 36.

  The phase difference determination unit 48 supplies the read phase 128 to the memory read control unit 32 so as to absorb the phase difference between the reception data 106 and 108 and adjust the path phase of the transmission data 130 and 132 to the same phase. To do.

  For example, as shown in FIG. 4, the data 106 and 108 received via the transmission lines 12 and 14 and written to the phase absorption memories 34 and 36 have a difference in reception phase between them. β is 8.5 frames. In the present apparatus 10, in order to absorb this phase difference β, the read phase 128 is determined based on the reception phase of the data 106 on the delayed side, in this example, on the transmission line 14 side.

  In this case, a time for detecting a bit error occurring in the transmission lines 12 and 14 by the error detection units 24 and 26, for example, a required delay amount γ is required. Therefore, the total delay amount α on the transmission line 14 side is the phase difference β + the delay amount γ. For example, when the B3 byte in the POH is used in the transmission path error determination, a transmission path error in a predetermined frame cannot be detected until the B3 byte of the next frame is received. In addition to the frame delay, a delay from the beginning of the next frame to the B3 byte position is required.

  Next, an operation example in which common stuff is detected by the stuff detection unit 30 of the uninterruptible switching circuit 10 in this embodiment will be described with reference to the timing chart of FIG.

  Here, the selection signal 120 for selecting the transmission path 12 is supplied from the selection control unit 28 to the stuff detection unit 30, and 1 is set as a predetermined threshold value in the threshold value excess determination units 76 and 78. To do. Further, it is assumed that a counter value of an initial value 0 is set in the UP / DOWN counters 72 and 74.

  In FIG. 5, the reception staffs 110 and 112 and the common staff 122 are shown separated for each frame. In addition, “P” and “N” shown in receiving staff 110 and 112, individual staff requests 176 and 178, and common staff 122 represent positive and negative staff, respectively, and if these staff are staffless Shows nothing.

  In this embodiment, first, at time t202, reception stuff information 110 indicating the correct stuff “P” is input from the pointer interpretation unit 20 to the UP / DOWN counter 72, and the counter value is counted up from 0 to 1. At this time, since the reception stuff information 112 from the pointer interpretation unit 22 indicates that there is no stuff, the counter value of the UP / DOWN counter 74 remains at the initial value 0.

  As a result, in the UP / DOWN counter 72, the fluctuation amount 172 of the transmission line 12 becomes “+1”, the writing phase of the transmission line 12 is delayed by one clock, that is, the accumulation delay amount of the phase absorption memory 34 is reduced by 1 byte. It will be. Further, the fluctuation amount 174 of the transmission line 14 remains 0, and the accumulation delay amount of the phase absorption memory 36 does not change.

  Next, the fluctuation amounts 172 and 174 are supplied from these counters 72 and 74 to the threshold excess determination units 76 and 78.

  In the determination unit 76, when the variation amount 172 of “+1” reaches the predetermined threshold value “1”, the correct staff “P” is output as the individual staff request 176 of the transmission path 12.

  When the individual staff request 176 indicating the regular staff “P” is supplied to the staff selection unit 80, the selection signal 80 for selecting the transmission path 12 is supplied to the selection unit 80. 176 is selected. In addition, the selection unit 80 outputs the individual staff request 176 indicating the regular staff “P” as the common staff 122.

  The common stuff 122 indicating the positive stuff “P” is supplied to the memory read control unit 32, and the control unit 32 delays the read phase of the phase absorption memory 34 by one clock according to the common positive stuff 122. That is, reading from the memory 34 is stopped for one clock. Thus, by generating the common positive stuff 122, the accumulated delay amount of the phase absorption memory 34 is maintained at the same value as the current delay amount.

  Further, this common positive stuff 122 is also supplied to the counters 72 and 74, and 1 is subtracted from the respective counter values. Therefore, as shown at time t204, the counter value 172 of the transmission line 12 is set to 0, and the transmission line The counter value 174 of 14 becomes -1.

  Here, in the threshold excess determination unit 78, negative stuff “N” is output as the individual stuff request 176 of the transmission line 14 according to the counter value 174 of −1, but the selection signal 120 in the stuff selection unit 80 is transmitted. Since the path 14 is not selected, the common staff 122 is not generated.

  At this time, since the read phase of the memory 34 is delayed by one clock, the accumulated delay amount of the phase absorption memory 36 of the transmission line 14 is larger by one byte than the current delay amount. That is, the counters 72 and 74 correct the accumulated delay amount by updating the counter value according to the common stuff 122 generated for the previous frame.

  Next, as shown at time t206, when the reception stuff information 110 of the transmission path 12 becomes the correct stuff `` P '' again, the common correct stuff 122 is output from the stuff selection unit 80 in the same manner as the process at time t202, The read phase of the phase absorption memory 34 is again delayed by one clock.

  Further, as shown at time t208, in the UP / DOWN counter 74, the counter value of the transmission line 14 is subtracted to -2 according to the common positive stuff 122, so that the phase absorption memory 36 of the transmission line 14 The accumulated delay amount is 2 bytes larger than the current delay amount.

  Next, as shown at time t210, when the reception stuff information 112 of the transmission line 14 becomes the correct stuff "P", the UP / DOWN counter 74 of the transmission line 14 is counted up and the counter value 174 becomes -1. . However, in the threshold determination in the threshold excess determination unit 78, a new individual staff request 178 is not generated, and the transmission line 14 is not selected in the staff selection unit 80, so the common staff 122 is not generated.

  At this time, since the writing phase of the transmission line 14 is delayed by one clock, the accumulated delay amount of the phase absorption memory 36 of the transmission line 14 is decreased by 1 byte and becomes a value larger by 1 byte than the current delay amount.

  From time t212 to t224, the same operation as described above is performed.

  Since the transmission lines 12 and 14 are affected by the transmission distance and the processing of the relay transmission apparatus interposed in the middle, the staff information is not always received at the same time, and the interval at which the staff information is received also varies. . However, since the original data is the same, the number and frequency of reception of the stuff information in the circuit 10 is considered to be the same on average between the transmission lines 12 and 14.

  As shown in FIG. 5, while the 22 frames of data are received from the transmission lines 12 and 14, four correct stuffs are detected as the reception stuffs 110 and 112 in the pointer interpretation units 20 and 22. Thus, since the number of times the stuff information is received via the transmission lines 12 and 14 is the same ratio on average, in this embodiment, the UP / DOWN counters 72 and 74 of both transmission lines 12 and 14 are: It operates so as to maintain 0, that is, operates so as to keep the accumulation delay amount of the phase absorption memories 34 and 36 constant.

  In the present embodiment, only the case where the positive stuff is detected as the reception stuff is shown, but even when the negative stuff is detected, the basic operation is the same and is realized by performing the reverse operation for the required processing. .

  Other operations in the circuit 10 such as controlling the readout phase of the phase absorption memories 34 and 36 using the detected common stuff may use known techniques, and the description thereof is omitted here.

It is a block diagram which shows one Example of the uninterruptible switching circuit which concerns on this invention. It is a block diagram which shows the SDH transmission apparatus with which the uninterruptible switching circuit of the Example shown in FIG. 1 is applied. It is a block diagram which shows the stuff | seat detection part in the uninterruptible switching circuit of the Example shown in FIG. FIG. 2 is a diagram schematically showing data stored in a shift register in the synchronous reproduction circuit of the embodiment shown in FIG. 1. It is a timing chart explaining the operation | movement procedure in the staff detection part of the Example shown in FIG.

Explanation of symbols

10 Non-instantaneous switching circuit
12, 14 Transmission line
16, 18 Reception processing section
20, 22 Pointer interpreter
24, 26 Error detector
28 Selection control section
30 Staff detector
32 Memory read controller
34, 36 Phase absorption memory
38 Selection section
40, 42 MF detector
44, 46 Memory write controller
48 Phase difference judgment unit

Claims (10)

Connected to at least two transmission lines, receives data transmitted through the transmission line, and for at least two data, an SDH (Synchronous Digital Hierarchy) transmission apparatus having at least two paths, In the uninterruptible switching circuit that selects and switches one of the at least two paths, the circuit includes:
A phase absorption memory for temporarily storing the data in order to synchronize and output the phase of the data;
Pointer interpretation means for extracting received staff information from the data;
By counting the reception stuff information, a fluctuation amount corresponding to a difference between the data delay amount of the current frame and the data delay amount accumulated in the phase absorption memory is detected, and based on the fluctuation amount A non-instantaneous switching circuit characterized by including common staff detection means for generating common staff.   The non-instantaneous switching circuit according to claim 1, wherein the common stuff detecting means counts up when the received stuff information is positive stuff, and counts down when the received stuff information is negative stuff to update the counter value. And the fluctuation amount is determined in accordance with the counter value.   3. The non-instantaneous switching circuit according to claim 2, wherein the counter counts down when the common stuff detecting means generates the previous common stuff for the previous frame and the previous common stuff is the correct stuff. A non-instantaneous switching circuit that corrects a delay amount of data accumulated in the phase absorption memory by counting up and updating the counter value in the case of negative stuff. The uninterruptible switching circuit according to claim 1, wherein the circuit includes selection control means for selecting one of the at least two paths.
The common staff detection unit obtains an individual staff request according to the variation amount, selects the individual staff request according to the selection by the selection control unit, and responds to the individual staff request selected in this way. A non-instantaneous switching circuit characterized by generating the common staff.   5. The non-instantaneous switching circuit according to claim 4, wherein the common staff detecting unit compares a predetermined threshold value set in advance with the fluctuation amount, and the fluctuation amount reaches the predetermined threshold value when the fluctuation amount reaches the predetermined threshold value. An uninterruptible switching circuit, comprising: a threshold excess determination unit that outputs the individual staff request according to received staff information. Connected to at least two transmission lines, receives data transmitted through the transmission line, and at least two paths for the at least two data in an SDH transmission apparatus having at least two paths In the common staff generation method for generating a common staff to select and switch between, the method includes:
A pointer interpretation step of extracting received staff information from the data;
An accumulation step of temporarily accumulating the data in a phase absorption memory to output the data in synchronization with the phase;
By counting the reception stuff information, a fluctuation amount corresponding to a difference between the data delay amount of the current frame and the data delay amount accumulated in the phase absorption memory is detected, and based on the fluctuation amount A common staff generation method comprising a common staff detection step of generating a common staff.   7. The common staff generation method according to claim 6, wherein the common staff detection step counts up when the received staff information is positive stuff, and counts down when the reception stuff information is negative stuff to update the counter value. And the variation amount is determined according to the counter value.   8. The common staff generation method according to claim 7, wherein the counting step counts down when the previous common staff is a normal staff when the previous common staff is generated in the common staff detection step for the previous frame. A method of generating a common stuff comprising correcting a delay amount of data accumulated in the phase absorption memory by counting up and updating the counter value in the case of negative stuff. The common staff generation method according to claim 6, wherein the method includes a selection control step of selecting one of the at least two routes.
The common staff detection step obtains an individual staff request according to the variation amount, selects the individual staff request according to the selection by the selection control step, and responds to the individual staff request selected in this way. And generating the common staff.   10. The common staff generation method according to claim 9, wherein the common staff detection step compares a predetermined threshold value set in advance with the fluctuation amount, and the reception is performed when the fluctuation amount reaches the predetermined threshold value. A common staff generation method comprising a threshold excess determination step of outputting the individual staff request according to staff information.

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