JP5285046B2 - Communication apparatus and communication method - Google Patents

Description

  The present invention relates to a communication device and a communication method for synchronizing a clock with an opposite device.

  In a communication system that transmits and receives data by synchronizing clocks, the communication device has a self-running mode that synchronizes with the clock generated by itself and a subordinate mode that synchronizes with the clock extracted from the received signal from the opposite device. Have.

  Such a communication apparatus needs to set the own apparatus to the subordinate mode when the opposite apparatus is in the self-running mode, and to set the own apparatus to the self-running mode when the opposite apparatus is in the subordinate mode. For this reason, in such a communication apparatus, the user has performed the work of confirming the clock mode of the opposite apparatus and setting the clock mode of the own apparatus.

  As a communication device that reduces the work burden on the user who sets the clock mode, there is one that switches the clock mode of the own device according to the determination result by determining the clock mode of the opposite device (see, for example, Patent Document 1). .

  The communication device described in Patent Document 1 includes a selector that outputs either a line clock extracted from a received signal from the opposite device or an internal clock generated by the own device. The communication apparatus compares the line clock and the internal clock with a frequency comparator. At this time, when the line clock and the internal clock have different frequencies, the communication apparatus switches to the selector mode to output the line clock and enters the subordinate mode. In addition, when the frequency of the line clock and the internal clock is the same, the communication apparatus switches to the self-running mode by switching the selector to output the internal clock.

JP-A-8-30350

  However, the device described in Patent Document 1 may not detect that the frequency is different if the frequency difference between the line clock and the internal clock is small even if the clock mode of the opposite device is the free-running mode. For this reason, what is described in Patent Document 1 is that the own device is switched to the self-running mode even though the opposite device is in the free-running mode, and the clock mode of the own device may not be set appropriately. There was a problem.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a communication device that can more appropriately set the clock mode of its own device in accordance with the clock mode of the opposite device.

The communication device of the present invention includes a reception clock extraction unit that extracts a reception clock from a reception signal from the opposite device, a self-running mode that generates and outputs a free-running clock, and a slave clock that is synchronized with the reception clock. Whether there is a frequency difference between the free-running clock and the reception clock by comparing the free-running clock and the reception clock with the clock generation unit that can be switched to any one of the clock modes of the dependent mode to be output A self-running clock frequency for controlling the clock generation unit to change and output a frequency of the free-running clock when the clock comparison unit does not detect that there is the frequency difference. a control unit outputs a control signal to said self-running mode to the clock generator when the device itself starts to operate, the If the frequency difference is detected to be the clock comparator unit, and, if the frequency difference is detected to be by the clock comparator unit after changing the frequency of said free-running clock, the said clock generator A clock mode control unit that outputs a control signal so as to be in a subordinate mode , wherein the clock generation unit can be switched to any one of the clock modes based on the control signal.

The communication method of the present invention comprises a free-running mode setting step of setting the own device to a self-running mode of operation using a free-running clock when the device itself starts operation, received from the receiving signal from the counter device A receiving clock extracting step for extracting a clock; a clock comparing step for detecting whether there is a frequency difference between the free-running clock and the receiving clock by comparing the free-running clock and the receiving clock; and the clock A self-running clock frequency control step of changing the frequency of the free-running clock when the frequency difference is not detected in the comparison step, and a received signal from the opposing device after the change of the frequency of the free-running clock A reception clock re-extraction step for re-extracting the reception clock from the frequency of the free-running clock; By comparing the free-running clock and the reception clock to detect whether there is a frequency difference between the free-running clock and the reception clock, in the clock comparison step or the clock re-comparison step when the frequency difference is detected to be the and a slave mode setting step of setting the own device to a slave mode to operate in the dependent clock that is synchronized with the receive clock.

  The present invention can provide a communication device that can set the clock mode of its own device more appropriately according to the clock mode of the opposite device.

It is a block diagram which shows the structure of the communication apparatus as the 1st Embodiment of this invention. It is a flowchart explaining operation | movement of the communication apparatus as the 1st Embodiment of this invention. It is a block diagram which shows the structure of the communication apparatus as the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the clock comparison part in the 2nd Embodiment of this invention. It is explanatory drawing of the rising edge detection pulse which the clock comparison part in the 2nd Embodiment of this invention detects. It is a flowchart explaining operation | movement of the communication apparatus as the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the communication apparatus as the 3rd Embodiment of this invention.

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

(First embodiment)
FIG. 1 shows the configuration of a communication device 1 as a first embodiment of the present invention.

  In FIG. 1, the communication device 1 includes a reception clock extraction unit 11, a clock generation unit 12, a clock comparison unit 13, a free-running clock frequency control unit 14, and a clock mode control unit 15. Further, the communication device 1 is communicably connected to the opposite device in a communication system that performs communication by synchronizing clocks. The opposing device is a communication device that transmits and receives data in either the self-running mode or the subordinate clock mode.

  The reception clock extraction unit 11 extracts a reception clock from the reception signal from the opposite device. For example, the reception clock extraction unit 11 may extract the reception clock from the reception signal in which the reception clock is superimposed on the data. Alternatively, the reception clock extraction unit 11 may receive a reception clock from a clock communication transmission line provided in parallel with the data communication transmission line. The extracted reception clock is input to the clock generation unit 12 and the clock comparison unit 13.

  The clock generation unit 12 generates a free-running clock. For example, the clock generation unit 12 includes a free-running oscillation circuit. The frequency of the free-running clock generated by the clock generator 12 is variable based on an external control signal.

  Further, the clock generation unit 12 generates a dependent clock synchronized with the reception clock.

  The clock generator 12 can be switched between a free-running mode for outputting a free-running clock and a dependent mode for outputting a dependent clock based on a control signal from the outside.

For example, the clock generation unit 12 generates a subordinate clock generation unit that generates a subordinate clock based on the received clock, a self-running clock generation unit that generates a free-running clock, and output clocks of the subordinate clock generation unit and the free-running clock generation unit. A switching unit for switching may be included. In this case, the free-running clock generator has a configuration that can change the frequency of the free-running clock based on a control signal from the free-running clock frequency controller 14 described later. Further, the switching unit switches and outputs the free-running clock and the dependent clock according to the control signal from the clock mode control unit 15. However, the clock generation unit 12 is not limited to the above-described configuration.

  The clock output from the clock generation unit 12 is used as a clock for transmitting a transmission signal by being output to the transmission unit included in the communication device 1. The clock output from the clock generation unit 12 is also input to the clock comparison unit 13.

  The clock comparison unit 13 detects whether there is a frequency difference between the reception clock and the free-running clock by comparing the reception clock and the free-running clock. The clock comparison unit 13 outputs a comparison result signal indicating whether there is a frequency difference to the free-running clock frequency control unit 14 and the clock mode control unit 15.

  The free-running clock frequency control unit 14 outputs a control signal for changing the frequency of the free-running clock to the clock generation unit 12 when the clock comparison unit 13 does not detect that there is a frequency difference between the reception clock and the free-running clock. To do.

  The clock mode control unit 15 outputs a control signal for setting the clock generation unit 12 to the free-running mode to the clock generation unit 12 and then detected by the clock comparison unit 13 that there is a frequency difference between the reception clock and the free-running clock. In this case, a control signal for switching to the subordinate mode is output to the clock generation unit 12. Further, the clock mode control unit 15 also detects that there is a frequency difference between the reception clock and the free-running clock by the clock comparison unit 13 after the free-running clock frequency control unit 14 changes the frequency of the free-running clock. A control signal for switching to the subordinate mode is output to the clock generator 12.

  That is, the clock mode control unit 15 sets the clock generation unit 12 to the free-running mode when the clock comparison unit 13 does not detect that there is a frequency difference between the reception clock and the free-running clock even after the free-running clock frequency is changed. Leave as it is.

  The clock mode setting operation of the communication apparatus 1 configured as described above will be described with reference to FIG. Note that the communication device 1 starts the following operation based on a start signal from a setting start switch (not shown).

  First, the clock mode control unit 15 outputs a control signal for setting the free-running mode to the clock generation unit 12. Thereby, the clock generation unit 12 outputs a free-running clock (step S1).

  Here, when a free-running clock is output from the clock generation unit 12, the communication device 1 transmits a transmission signal to the opposite device using the free-running clock. If the opposite device is in the subordinate mode, the opposite device transmits data using a clock subordinate to the self-running clock of the communication device 1. Alternatively, if the opposite device is in the free-running mode, it transmits data using a clock asynchronous to the free-running clock of the communication device 1.

  Next, the clock comparison unit 13 compares the reception clock extracted from the reception signal by the reception clock extraction unit 11 with the free-running clock output from the clock generation unit 12. Then, the clock comparison unit 13 outputs a comparison result signal indicating whether there is a frequency difference between the reception clock and the free-running clock (step S2).

  If it is not detected in step S2 that there is a frequency difference between the reception clock and the free-running clock, the case where the clock mode of the opposite device is the subordinate mode and the case where the opposite device is in the free-running mode, It can be considered that the frequency difference from the clock is very small. Therefore, the free-running clock frequency control unit 14 outputs a control signal for changing the frequency of the free-running clock to the clock generation unit 12, whereby the clock generation unit 12 outputs a free-running clock having the changed frequency ( Step S3).

  Here, when the free-running clock having the changed frequency is output from the clock generation unit 12, the communication device 1 transmits a transmission signal to the opposite device using the free-running clock having the changed frequency. If the opposite device is in the subordinate mode, the opposite device transmits data using a clock subordinate to the free-running clock of the communication device 1 whose frequency has been changed. Alternatively, in the self-running mode, the opposing device transmits data using a clock asynchronous to the free-running clock of the communication device 1 regardless of the change in the frequency of the free-running clock of the communication device 1.

  Next, the clock comparison unit 13 re-compares the reception clock re-extracted from the reception signal by the reception clock extraction unit 11 and the free-running clock output from the clock generation unit 12. Then, the clock comparison unit 13 outputs a comparison result signal indicating whether there is a frequency difference between the reception clock and the free-running clock (step S4).

  If it is not detected in step S4 that there is a frequency difference between the reception clock and the free-running clock, it is considered that the opposite device is in the subordinate mode. Therefore, the clock mode control unit 15 keeps the clock generation unit 12 in the free-running mode (step S5).

  On the other hand, if it is detected in step S2 or step S4 that there is a frequency difference between the reception clock and the free-running clock, the opposite device is considered to be in the free-running mode. Therefore, the clock mode control unit 15 outputs a control signal for switching to the subordinate mode to the clock generation unit 12. Thereby, the clock generation unit 12 outputs a dependent clock (step S6).

  Thus, the communication device 1 ends the clock mode setting operation.

  Note that the clock mode control unit 15 may count the number of comparisons by the clock comparison unit 13 in steps S2 and S4. Thus, the free-running clock frequency control unit 14 may change the frequency of the free-running clock until the number of comparisons reaches a predetermined threshold value, and the clock comparison unit 13 may perform re-comparison.

  Next, effects of the first exemplary embodiment of the present invention will be described.

  The communication apparatus according to the first embodiment of the present invention can set the clock mode of the own apparatus more appropriately according to the clock mode of the opposite apparatus.

  The reason is that the self-running clock frequency control unit changes the frequency of the free-running clock when there is a frequency difference between the received clock from the opposite device and the free-running clock generated in the own device. This is because the comparison unit compares the received clock with the free-running clock again. This is because it is possible to discriminate between the case where the opposite device is in the subordinate mode and the case where the opposite device is in the free-running mode but the frequency difference between the reception clock and the free-running clock is very small.

(Second Embodiment)
Next, a second embodiment of the present invention will be described in detail with reference to the drawings. Note that, in each drawing referred to in the description of the present embodiment, the same reference numerals are given to the same configuration and steps that operate in the same manner as in the first embodiment of the present invention, and the detailed description in the present embodiment. Description is omitted.

  FIG. 3 shows the configuration of the communication apparatus 2 as the second embodiment of the present invention. In FIG. 3, the communication device 2 is different from the communication device 1 according to the first embodiment of the present invention in that a clock comparison unit 23 is provided instead of the clock comparison unit 13.

  The clock comparison unit 23 detects the rising edges of the reception clock extracted by the reception clock extraction unit 11 and the free-running clock generated by the clock generation unit 12. The clock comparison unit 23 detects whether there is a frequency difference between the reception clock and the free-running clock by detecting a change in the phase difference of the detected rising edge detection pulse. Then, the clock comparison unit 23 outputs a comparison result signal indicating whether there is a change in phase difference to the free-running clock frequency control unit 14 and the clock mode control unit 15.

  For example, the clock comparison unit 23 may include rising edge detection circuits 231 and 232 and a pulse position comparison circuit 233 as shown in FIG.

  The rising edge detection circuit 231 detects the rising edge of the reception clock and outputs an edge detection pulse.

  The rising edge detection circuit 232 detects the rising edge of the free-running clock and outputs an edge detection pulse.

  The pulse position comparison circuit 233 outputs a signal that detects whether or not the difference between the positions of the detection pulses output from the rising edge detection circuits 231 and 232 changes.

  For example, an example of the edge detection pulse detected by the rising edge detection circuits 231 and 232 will be described with reference to FIG.

  In FIG. 5, (a) is an example of a reception clock, and (c) is an example of a free-running clock.

  The rising edge detection circuit 231 detects a rising edge with respect to the reception clock, and outputs an edge detection pulse as shown in (b).

  The rising edge detection circuit 232 detects a rising edge with respect to the free-running clock, and outputs an edge detection pulse as shown in (d).

  The pulse position comparison circuit 233 measures a time difference t between the edge detection pulse shown in (b) and the edge detection pulse shown in (d). Then, when the length of the time difference t changes, the pulse position comparison circuit 233 outputs a comparison result signal indicating that a change in the phase difference between the reception clock and the free-running clock has been detected.

  Further, when the length of the time difference t does not change, the pulse position comparison circuit 233 outputs a comparison result signal indicating that a change in the phase difference between the reception clock and the free-running clock is not detected.

  The pulse position comparison circuit 233 can be configured by a counter using a high-speed clock capable of measuring the time difference t.

  The clock mode setting operation of the communication apparatus 2 configured as described above will be described with reference to FIG.

  The communication device 2 executes steps S12 and S14 instead of steps S2 and S4 with respect to the clock mode setting operation of the communication device 1 as the first embodiment of the present invention described with reference to FIG. The point to do is different.

  In addition, the communication apparatus 2 shall start the following operation | movement based on the start signal from a setting start switch similarly to the communication apparatus 1 as the 1st Embodiment of this invention.

  First, the clock mode control unit 15 sets the clock generation unit 12 to the free-running mode (step S1).

  Next, the clock comparison unit 23 detects the rising edges of the reception clock and the free-running clock extracted from the reception signal, and compares the phase differences. Then, the clock comparison unit 23 generates a comparison result signal indicating whether or not a change in phase difference has been detected (step S12).

  If no change in phase difference is detected in step S12, the free-running clock frequency control unit 14 outputs a control signal for changing the frequency of the free-running clock to the clock generation unit 12 (step S3).

  Then, the clock comparison unit 23 detects the rising edge of the received clock and the free-running clock re-extracted from the received signal, and re-compares the phase difference. Then, the clock comparison unit 23 generates a comparison result signal indicating whether or not a change in phase difference has been detected (step S14).

  If no change in phase difference is detected in step S14, the clock mode control unit 15 leaves the clock generation unit 12 in the free-running mode, assuming that the opposing device is in the subordinate mode (step S5).

  On the other hand, when a change in phase difference is detected in step S12 or step S14, the clock mode control unit 15 switches the clock generation unit 12 to the subordinate mode, assuming that the opposing device is in the free-running mode (step S6).

  Thus, the communication device 2 ends the clock mode setting operation.

  Next, the effect of the second exemplary embodiment of the present invention will be described.

  The communication apparatus as the second embodiment of the present invention can set the clock mode of the own apparatus more appropriately according to the clock mode of the opposite apparatus.

  The reason is that the clock comparator 23 detects a change in the phase difference of the rising edge detection pulse detected from the reception clock and the free-running clock, and the frequency between the reception clock from the opposite device and the free-running clock generated in the self-device. This is because if the difference cannot be detected, the free-running clock frequency control unit changes the frequency of the free-running clock, and the clock comparison unit compares the received clock with the free-running clock again. This is because it is possible to discriminate between the case where the opposite device is in the subordinate mode and the case where the opposite device is in the free-running mode but the frequency difference between the reception clock and the free-running clock is very small.

  Moreover, the communication apparatus as the second embodiment of the present invention realizes a communication apparatus that can set the clock mode of the own apparatus more appropriately according to the clock mode of the opposite apparatus with a simpler configuration. be able to.

  The reason is described. For example, the apparatus described in Patent Document 1 performs comparison using counters provided for the reception clock and the free-running clock in order to compare the frequencies of the reception clock and the free-running clock. For this reason, the apparatus described in Patent Document 1 requires two counters having the same configuration.

  In contrast, the communication apparatus according to the second embodiment of the present invention detects the rising edges of the reception clock and the free-running clock for comparison and recomparison of the frequencies of the reception clock and the free-running clock. A clock comparison unit that detects whether or not the phase difference changes by using one counter is used. Therefore, the communication device as the second exemplary embodiment of the present invention can configure the clock comparison unit with a smaller number of counters than that described in Patent Document 1.

  Thus, in the communication apparatus as the second embodiment of the present invention, the clock comparison unit detects whether or not the phase difference between the rising edge detection pulses of the reception clock and the free-running clock changes. Therefore, a simpler configuration than that described in Patent Document 1 can be adopted.

(Third embodiment)
Next, a third embodiment of the present invention will be described in detail with reference to the drawings. Note that, in each drawing referred to in the description of the present embodiment, the same configurations and steps that operate in the same manner as in the first and second embodiments of the present invention are denoted by the same reference numerals, and the present embodiment. The detailed description in is omitted.

  FIG. 7 shows the configuration of the communication apparatus 3 as the third embodiment of the present invention. In FIG. 7, the communication device 3 is different from the communication device 2 as the second embodiment of the present invention in that a communication signal 3 includes a reception signal disconnection detection unit 37 and a clock mode setting start unit 38.

  The reception signal disconnection detection unit 37 detects whether or not the reception signal from the opposing device is disconnected. For example, the reception signal disconnection detection unit 37 outputs a reception signal disconnection detection signal to the clock mode setting start unit 38 when detecting the disconnection or release of the reception signal by monitoring the reception signal. Here, the reception signal disconnection detection signal is a signal that is “1” while the reception signal disconnection is detected and “0” while the reception signal disconnection is cancelled.

  The clock mode setting start unit 38 receives the reception signal disconnection detection signal output from the reception signal disconnection detection unit 37. Then, the clock mode setting start unit 38, when the received reception signal disconnection detection signal changes from “1” indicating disconnection to “0” indicating cancellation, the clock comparison unit 23, the free-running clock frequency control unit 14 and the clock mode controller 15 are started.

  The operation of the communication device 3 configured as described above will be described. Here, the communication apparatuses 1 and 2 as the first and second embodiments of the present invention have started the clock mode setting operation based on the start signal from the setting start switch.

  On the other hand, in the communication apparatus 3 as the third embodiment of the present invention, first, the reception signal disconnection detection unit 37 detects the reception signal disconnection or the release thereof, and sets the reception signal disconnection detection signal to the clock mode. Output to the start unit 38.

  Next, the clock mode setting start unit 38 detects a time point when the received reception signal disconnection detection signal changes from “1” to “0” (that is, a time point when the reception signal starts to be input).

  The clock mode setting start unit 38 outputs a clock mode setting start signal to the clock mode control unit 15.

  The clock mode control unit 15 that has acquired the clock mode setting start signal executes the clock mode setting operation in the same manner as the communication device 2 according to the second embodiment of the present invention described with reference to FIG.

  Thus, the communication device 3 ends the operation.

  Next, effects of the third exemplary embodiment of the present invention will be described.

  The communication apparatus according to the third embodiment of the present invention reduces the operation burden on the user in the communication apparatus that can more appropriately set the clock mode of the own apparatus according to the clock mode of the opposite apparatus. Can do.

  The reason is that the clock mode setting start unit starts the clock mode setting operation when the reception signal disconnection detection unit detects a time point when the reception signal changes from disconnection to release. This is because the user does not need to operate the setting start switch.

  It should be noted that the above-described embodiments can be implemented in combination as appropriate.

  The present invention is not limited to the above-described embodiments, and can be implemented in various modes.

1, 2, 3 Communication device 11 Reception clock extraction unit 12 Clock generation unit 13, 23 Clock comparison unit 14 Free-running clock frequency control unit 15 Clock mode control unit 37 Reception signal disconnection detection unit 38 Clock mode setting start unit 231 Rising edge detection Circuit 232 Rising edge detection circuit 233 Pulse position comparison circuit

Claims (5)

A reception clock extraction unit that extracts a reception clock from a reception signal from the opposite device;
A clock generation unit capable of switching to a clock mode between a free-running mode for generating and outputting a free-running clock and a subordinate mode for outputting a subordinate clock synchronized with the reception clock;
A clock comparison unit that detects whether there is a frequency difference between the free-running clock and the reception clock by comparing the free-running clock and the reception clock;
A self-running clock frequency control unit that controls the clock generation unit to change and output the frequency of the free-running clock when the clock comparison unit does not detect that there is the frequency difference;
In the case where the information processing apparatus outputs a control signal to said self-running mode to the clock generator when starting the operation, the frequency difference is detected to be by the clock comparator unit, and the frequency of said free-running clock of if it is detected that there is the frequency difference by the clock comparator unit after the change, and a clock mode control section for outputting a control signal to the slave mode to the clock generator,
The clock generator is
A communication apparatus capable of switching to any one of the clock modes based on the control signal .   The clock comparison unit detects the rising edges of the reception clock and the free-running clock, and detects whether the phase difference of the detected rising edge detection pulse changes to determine whether the frequency difference exists. The communication device according to claim 1, wherein the communication device detects whether or not. A reception signal disconnection detection unit for detecting whether the reception signal from the opposing device is disconnected,
A clock mode setting start unit that operates the clock comparison unit, the free-running clock frequency control unit, and the clock mode control unit when the reception signal disconnection is released based on detection by the reception signal disconnection detection unit;
The communication apparatus according to claim 1, further comprising: A free-running mode setting step of setting the own device to a self-running mode of operation using a free-running clock when the device itself starts to operate,
A reception clock extraction step of extracting a reception clock from the reception signal from the opposite device;
A clock comparison step of detecting whether there is a frequency difference between the free-running clock and the reception clock by comparing the free-running clock and the reception clock; and
A free-running clock frequency control step of changing the frequency of the free-running clock when it is not detected that there is the frequency difference in the clock comparison step;
A reception clock re-extraction step for re-extracting the reception clock from the reception signal from the opposite device after the change of the frequency of the free-running clock;
A clock re-comparison step for detecting whether there is a frequency difference between the free-running clock and the reception clock by comparing the free-running clock and the reception clock after changing the frequency of the free-running clock;
When the frequency difference is detected to be at the clock comparison step or said clock re-comparing step, a slave mode setting step of setting the own device to a slave mode to operate in the dependent clock that is synchronized with the reception clock ,
A communication method comprising:   In the clock comparison step and the clock re-comparison step, the rising edges of the reception clock and the free-running clock are detected, and the change in the phase difference of the detected rising edge detection pulse is detected. The communication method according to claim 4, wherein whether or not there is present is detected.

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