JP5413662B2 - Elastic buffer device, transceiver, and timing adjustment code transmission method for elastic buffer device - Google Patents

Description

  The present invention relates to an elastic buffer device, a transceiver, and a timing adjustment code transmission method for the elastic buffer device, and more particularly to an elastic buffer device used for absorbing a clock frequency difference between a transmission side and a reception side, and transmission / reception. The present invention relates to a timing adjustment code transmission method for a machine and an elastic buffer device.

  When data is transferred between digital circuits having different clock frequencies between the transmission side and the reception side, an elastic buffer can be used to transfer the data without interruption.

  The configuration of the elastic buffer is disclosed in Patent Document 1, for example.

  By the way, in the elastic buffer, since the clock frequency is different between the transmission side and the reception side, the write pointer position of the buffer comes to the read pointer position, and unread data is destroyed (hereinafter referred to as overrun). is there. Conversely, the read pointer position of the buffer may come to the write pointer position, and invalid data may be read from the read or unwritten storage location (hereinafter referred to as underrun).

  In order to prevent overrun and underrun, for example, Non-Patent Document 1 describes the insertion and deletion of Fill Word (corresponding to the timing adjustment code). Fill Word is an insignificant code (IDLE). By inserting and deleting this Fill Word, overrun and underrun caused by the clock frequency between the sending side and the receiving side are prevented. Further, in Non-Patent Document 1, the number of transmission / reception words that can cause overrun or underrun is calculated from the clock frequency error defined in the interface specifications, and Fill Word (timing adjustment code) is transmitted at the corresponding period. It stipulates that

JP 2006-067107 (paragraph 0020, etc.)

Annex A, “A.2 Clock skew Mamagement”, page 103 and Annex G, “G.2 Clock skew management function periodicity” page 117, Fiber Channel-Arbitrated Loop, FC-AL-2 rev 7.0, April 1, 1999

  However, if the actual clock frequency error is smaller than the value defined in the specification, it is not necessary to send the timing adjustment code at intervals defined in the specification.

  If the actual clock frequency error is larger than the value determined by the specification, overrun or underrun cannot be prevented even if the timing adjustment code is transmitted at intervals determined by the specification.

An elastic buffer device according to the present invention temporarily stores received data generated based on a first clock frequency, and synchronizes to a second clock frequency.
In the buffer, an overrun state that destroys or attempts to destroy unread data and an underrun state that reads or reads read or invalid data are detected, and the overrun state or the underrun state is detected. An overrun / underrun detector that outputs a detection signal;
Timing for generating a transmission request for the second timing adjustment code when receiving at least one of the detection signal from the overrun / underrun detection unit and the first timing adjustment code received as received data An adjustment code transmission control unit;
A transmission data arbitration unit that performs transmission data arbitration between the transmission of the second timing adjustment code and the packet transmission based on the transmission request from the timing adjustment code transmission control unit;
Equipped with a,
The timing adjustment code transmission control unit has a timer for measuring an elapsed time from an initial value,
The timing adjustment code transmission control unit receives at least one of the detection signal and the first timing adjustment code received as received data from the overrun / underrun detection unit, and the elapsed time Is greater than the shortest cycle for transmitting the second timing adjustment code, a second timing adjustment code transmission request is generated,
The elastic buffer device is characterized in that when the first timing adjustment code is received, the value of the timer is set to the initial value .
Further, an elastic buffer device according to the present invention temporarily stores received data generated based on a first clock frequency and performs synchronization with the second clock frequency,
In the buffer, an overrun state that destroys or attempts to destroy unread data and an underrun state that reads or reads read or invalid data are detected, and the overrun state or the underrun state is detected. An overrun / underrun detector that outputs a detection signal;
Timing for generating a transmission request for the second timing adjustment code when receiving at least one of the detection signal from the overrun / underrun detection unit and the first timing adjustment code received as received data An adjustment code transmission control unit;
A transmission data arbitration unit that performs transmission data arbitration between the transmission of the second timing adjustment code and the packet transmission based on the transmission request from the timing adjustment code transmission control unit;
With
The buffer is configured to prevent the overrun state or the underrun state by deleting the first timing adjustment code received as the received data and inserting a third timing code into the received data. This is an elastic buffer device.

A timing adjustment code transmission method for an elastic buffer device according to the present invention includes a buffer for temporarily storing received data generated based on a first clock frequency and performing synchronization with the second clock frequency. In the elastic buffer device timing adjustment code transmission method,
Detecting an overrun condition in the buffer that destroys or tries to destroy unread data, or an underrun condition that reads or reads read or invalid data;
When the overrun state or the underrun state is detected or the first timing adjustment code is received as received data, a transmission request for the second timing adjustment code is generated,
Based on the transmission request, either one of transmission of the second timing adjustment code and packet transmission is transmitted ,
The elastic buffer device has a timer for measuring an elapsed time from an initial value,
When the overrun state or the underrun state is detected or the first timing adjustment code is received as received data, and the elapsed time is longer than the shortest cycle for transmitting the second timing adjustment code To generate a transmission request for the second timing adjustment code,
A timing adjustment code transmission method for an elastic buffer device, wherein the timer value is set to the initial value when the first timing adjustment code is received .
The elastic buffer device timing adjustment code transmission method according to the present invention also includes a buffer for temporarily storing received data generated based on the first clock frequency and performing synchronization with the second clock frequency. In the elastic buffer device provided timing adjustment code transmission method,
Detecting an overrun condition in the buffer that destroys or tries to destroy unread data, or an underrun condition that reads or reads read or invalid data;
When the overrun state or the underrun state is detected or the first timing adjustment code is received as received data, a transmission request for the second timing adjustment code is generated,
Based on the transmission request, either one of transmission of the second timing adjustment code and packet transmission is transmitted,
The buffer is configured to prevent the overrun state or the underrun state by deleting the first timing adjustment code received as the received data and inserting a third timing code into the received data. And a timing adjustment code transmission method of the elastic buffer device.

  In the present application, a state in which unread data is destroyed or about to be destroyed in the buffer is referred to as an overrun state, and a state in which the read or invalid data is read or read from the buffer is referred to as an underrun state.

  The present invention has the following effects.

  In the present invention, the timing adjustment code is transmitted / received depending on the buffer state. Therefore, when the actual clock frequency difference is smaller than the interface specified value, the timing adjustment code is transmitted / received at an interval larger than the specified interval. The interface is effectively used.

  Also, even when the actual clock frequency difference becomes larger than the specified value of the interface due to a failure or the like, the timing adjustment code is transmitted / received when the buffer overrun or underrun condition is detected. The operation can be continued without causing an underrun.

It is a block diagram which shows one Embodiment of the elastic buffer apparatus concerning this invention. It is a flowchart which shows operation | movement of a timing adjustment code transmission control part. It is a block diagram which shows the communication system using the transmitter / receiver provided with the elastic buffer apparatus of this embodiment.

  Hereinafter, typical embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing an embodiment of an elastic buffer device according to the present invention.

  The buffer 11 is a synchronization buffer having an insert delete function for timing adjustment codes in order to prevent overrun / underrun. When the received data includes a timing adjustment code, the buffer 11 prevents overrun / underrun by deleting the timing adjustment code or newly inserting a timing adjustment code. The write pointer 12 is a pointer for writing received data to the buffer 11. The read pointer 13 is a pointer for reading the synchronization reception data from the buffer 11.

  The overrun / underrun detection unit 14 detects an overrun state or an underrun state from the difference between the output of the write pointer 12 and the output of the read pointer 3.

  The timing adjustment code transmission control unit 15 has a timer 16 for measuring the elapsed time from the initial value and generates a timing adjustment code transmission request. The transmission request for the timing adjustment code is based on the detection signal from the overrun / underrun detection unit 14, the timing adjustment code received as received data (becomes the first timing adjustment code), and the value of the timer 16. Generated. The timing adjustment code transmission control unit 15 sends a transmission request for a timing adjustment code (which becomes the second timing adjustment code) to the transmission data arbitration unit 17 as necessary. The timing adjustment code transmission control unit 15 receives a timing adjustment code (becomes the first timing adjustment code) and sends back a return timing adjustment code (becomes the second timing adjustment code) in response to a timing adjustment code transmission request. Is also included.

  The transmission data arbitration unit 17 performs transmission data arbitration between timing adjustment code transmission from the timing adjustment code transmission control unit 15 and packet transmission.

  When an overrun or underrun state is detected by the overrun / underrun detection unit 14 from the difference between the output of the write pointer 12 and the output of the read pointer 13, a detection signal is notified to the timing adjustment code transmission control unit 15 Is done.

  Upon receiving the detection of the overrun state or the underrun state, the timing adjustment code transmission control unit 15 issues a timing adjustment code transmission request to the transmission data arbitration unit 17 in a state where the conditions are met. Transmission data arbitration unit 17 arbitrates transmission data and transmits a timing adjustment code. In the counterpart node that has received the timing adjustment code, the received timing adjustment code is input to the timing adjustment code transmission control unit 15 '(not shown), and the timing adjustment code is transmitted back.

  Note that FIG. 1 shows an elastic buffer device at one node, and the partner node connected to this node has an elastic buffer device having the same configuration.

  Next, the operation of the timing adjustment code transmission control unit 15 will be described with reference to FIG.

  The value of the timer 16 built in the timing adjustment code transmission control unit 15 is compared with a preset MAX cycle. The MAX cycle is the maximum cycle for transmitting the timing adjustment code. If it is determined that periodic transmission is not necessary, the MAX cycle is set to an infinite value so that the timing adjustment code is not transmitted periodically. it can. If the timer 16 has not exceeded the MAX cycle (step S21), it is determined whether a timing adjustment code has been received (step S22).

  If the timing adjustment code is not received in step S22, it is determined whether or not an overrun / underrun state is detected (step S23). If the overrun / underrun state is not detected in step S23, the process returns to the comparison between the value of the timer 16 and the MAX cycle (step S21).

  When the value of the timer 16 is larger than the MAX cycle (step S21) or when the timing adjustment code is received (step S22), the value of the timer 16 is set to the initial value 0 (here, the initial value is set to 0, but other values may be used). (28), a timing adjustment code transmission request is issued (step S29), and the process waits until the value of the timer 16 exceeds the MIN period (step S30). The MIN period is the shortest period for transmitting the timing adjustment code, and is a value for preventing frequent transmission of the timing adjustment code. In addition, the MIN period is a value for preventing continuous transmission and reception due to the return of the timing adjustment code. It is a value larger than the maximum latency of round trip between. When the value of the timer 16 exceeds the MIN period (step S30), the process returns to the comparison between the value of the timer 6 and the MAX period (step S21).

  When the overrun / underrun state is detected (step S23), the value of the timer 16 is compared with the MIN cycle (step S24). Wait until the value of the timer 16 exceeds the MIN period. When the value exceeds the MIN period (step S24), a timing adjustment code transmission request is issued (step S25), and reception of the timing adjustment code is awaited (step S26). When the timing adjustment code is received (step S26), the value of the timer 16 is returned to the initial value 0 (step S27), and the process returns to the comparison between the value of the timer 16 and the MAX cycle (step S21).

  In the present embodiment, the reception data generated based on the first clock frequency is temporarily stored, and the buffer overrun state and underrun state for synchronization with the second clock frequency are detected, Since the timing adjustment code is transmitted and received, if the actual clock frequency error is smaller than the value defined in the specification, the number of times the timing adjustment code is transmitted and received is reduced. Even if the actual clock frequency error is larger than the value specified in the specification, the timing adjustment code is transmitted and received at intervals shorter than the interval specified in the specification. Can be prevented.

  In this way, in this embodiment, the overrun / underrun state of the buffer is detected, the timing adjustment code is transmitted at that timing, and the timing adjustment code is received at the return time, so that overrun / under Runs can be prevented, and timing adjustment codes can be transmitted and received only when necessary.

  FIG. 3 is a block diagram showing a communication system using a transceiver having the elastic buffer device of the present embodiment.

  In FIG. 3, the transceiver 100 is synchronized from the elastic buffer unit 101 (which becomes the elastic buffer device of the present embodiment) that synchronizes received data with the clock frequency of the transceiver 100, and the elastic buffer unit 101. It has a transmission / reception unit 102 that demodulates the received data by frequency conversion, and a signal processing unit 103 that processes the demodulated reception data for voice and data signals. Transmission data output from the signal processing unit 103 is frequency-converted and modulated by the transmission / reception unit 102 and sent to the transceiver 200.

  The transceiver 200 includes an elastic buffer unit 201 (which becomes an elastic buffer device of the present embodiment) that synchronizes received data with the clock frequency of the transceiver 200, and frequency of received data synchronized from the elastic buffer unit 201. A transmission / reception unit 202 that performs conversion and demodulation, and a signal processing unit 203 that performs signal processing on the demodulated reception data for voice and data signals. Transmission data output from the signal processing unit 203 is frequency-converted and modulated by the transmission / reception unit 202 and sent to the transceiver 100.

  In the embodiment described above, an example in which an elastic buffer device is used as a transceiver has been described. However, the present invention transfers data without interruption when data is transferred between digital circuits having different clock frequencies. Therefore, any device using a buffer can be applied.

  The present invention can be suitably applied to an apparatus using a buffer for transferring data without interruption when the data is transferred between digital circuits having different clock frequencies, particularly to a transceiver.

11 Buffer 12 Write Pointer 13 Read Pointer 14 Overrun / Underrun Detection Unit 15 Timing Adjustment Code Transmission Control Unit 16 Timer 17 Transmission Data Arbitration Unit 100, 200 Transceiver 101, 201 Elastic Buffer Unit 102, 202 Transceiver 103, 203 Signal processor

Claims (7)

A buffer for temporarily storing received data generated based on the first clock frequency and synchronizing to the second clock frequency;
In the buffer, an overrun state that destroys or attempts to destroy unread data and an underrun state that reads or reads read or invalid data are detected, and the overrun state or the underrun state is detected. An overrun / underrun detector that outputs a detection signal;
Timing for generating a transmission request for the second timing adjustment code when receiving at least one of the detection signal from the overrun / underrun detection unit and the first timing adjustment code received as received data An adjustment code transmission control unit;
A transmission data arbitration unit that performs transmission data arbitration between the transmission of the second timing adjustment code and the packet transmission based on the transmission request from the timing adjustment code transmission control unit;
With
The timing adjustment code transmission control unit has a timer for measuring an elapsed time from an initial value,
The timing adjustment code transmission control unit receives at least one of the detection signal and the first timing adjustment code received as received data from the overrun / underrun detection unit, and the elapsed time Is greater than the shortest cycle for transmitting the second timing adjustment code, a second timing adjustment code transmission request is generated,
An elastic buffer device, wherein the timer value is set to the initial value when the first timing adjustment code is received. A buffer for temporarily storing received data generated based on the first clock frequency and synchronizing to the second clock frequency;
In the buffer, an overrun state that destroys or attempts to destroy unread data and an underrun state that reads or reads read or invalid data are detected, and the overrun state or the underrun state is detected. An overrun / underrun detector that outputs a detection signal;
Timing for generating a transmission request for the second timing adjustment code when receiving at least one of the detection signal from the overrun / underrun detection unit and the first timing adjustment code received as received data An adjustment code transmission control unit;
A transmission data arbitration unit that performs transmission data arbitration between the transmission of the second timing adjustment code and the packet transmission based on the transmission request from the timing adjustment code transmission control unit;
With
The buffer is configured to prevent the overrun state or the underrun state by deleting the first timing adjustment code received as the received data and inserting a third timing code into the received data. Elastic buffer device. The elastic buffer device according to claim 1 or 2 ,
A write pointer for writing the received data to the buffer;
A read pointer for reading the received data synchronized from the buffer,
The overrun / underrun detection unit detects the overrun state and the underrun state from a difference between an output of the write pointer and an output of the read pointer, and outputs the detection signal. Elastic buffer device to do. A transceiver comprising the elastic buffer device according to any one of claims 1 to 3 . In a timing adjustment code transmission method for an elastic buffer device including a buffer for temporarily storing reception data generated based on a first clock frequency and performing synchronization with the second clock frequency,
Detecting an overrun condition in the buffer that destroys or tries to destroy unread data, or an underrun condition that reads or reads read or invalid data;
When the overrun state or the underrun state is detected or the first timing adjustment code is received as received data, a transmission request for the second timing adjustment code is generated,
Based on the transmission request, either one of transmission of the second timing adjustment code and packet transmission is transmitted,
The elastic buffer device has a timer for measuring an elapsed time from an initial value,
When the overrun state or the underrun state is detected or the first timing adjustment code is received as received data, and the elapsed time is longer than the shortest cycle for transmitting the second timing adjustment code To generate a transmission request for the second timing adjustment code,
A timing adjustment code transmission method for an elastic buffer device, wherein the timer value is set to the initial value when the first timing adjustment code is received. In a timing adjustment code transmission method for an elastic buffer device including a buffer for temporarily storing reception data generated based on a first clock frequency and performing synchronization with the second clock frequency,
Detecting an overrun condition in the buffer that destroys or tries to destroy unread data, or an underrun condition that reads or reads read or invalid data;
When the overrun state or the underrun state is detected or the first timing adjustment code is received as received data, a transmission request for the second timing adjustment code is generated,
Based on the transmission request, either one of transmission of the second timing adjustment code and packet transmission is transmitted,
The buffer is configured to prevent the overrun state or the underrun state by deleting the first timing adjustment code received as the received data and inserting a third timing code into the received data. A method for transmitting a timing adjustment code of an elastic buffer device. In the elastic buffer device timing adjustment code transmission method according to claim 5,
  The buffer is configured to prevent the overrun state or the underrun state by deleting the first timing adjustment code received as the received data and inserting a third timing code into the received data. A method for transmitting a timing adjustment code of an elastic buffer device.

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