JP2008109268A - Synchronization communication method of communication apparatus and its synchronization device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively synchronize a plurality of communication apparatuses in a transmission path with high accuracy even when the communication apparatuses are connected in series with the transmission path in a transmission system where the plurality of communication apparatuses in the transmission path receive transmission data from a communication apparatus for managing reference time and operates in synchronism with the reference time although, when the transmission path and the communication apparatuses are connected in series, there is increased a difference of reception times of transmission data between the transmission apparatuses owing to delay in a relaying communications apparatuses by transfer processing in addition to propagation delay of a signal so that each communication apparatus is needed to correct the transmission path delay. <P>SOLUTION: There are packaged on the communication apparatuses 1, 2 a relaying path not mediating a memory device and a return path, and switches 223, 233, a CPU 140 of the communication apparatus 1 for managing the reference time instructs changeover of the return path from the transmission path to measure the transmission path delay and simultaneously a CPU 240 of a communication apparatus 2, a measurement object executes synchronization correction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method in which all communication devices connected to a transmission line are synchronized with a reference time in a transmission system, and the synchronous communication device.

  In order for all communication devices connected to the transmission path to synchronize with the reference time in the transmission system, the communication device managing the reference time needs to notify the reference time to the other communication devices. At this time, when the communication devices are connected in parallel to the transmission line, the difference in the transmission line delay time between the communication devices becomes a difference in signal propagation time, which is an extremely small value. Therefore, even if the in-device reference timer is set to the reference time at the timing when the transmission data is received from the communication device that manages the reference time, the time difference between the communication devices is small. On the other hand, when the communication device is connected in series to the transmission line, the transfer time in the communication device is added in addition to the signal propagation time. Increase. For this reason, in order for a plurality of communication devices to operate synchronously, it is necessary to perform time correction based on the transmission line delay time on the in-device reference timer of each communication device.

  As an example of calculating the transmission line delay time, the return delay time (the time required for data to reciprocate) between the communication apparatus managing the reference time and each communication apparatus is measured, and the time required for the forward path and the return path are equal. As a premise, there is a method of calculating a delay time to each communication device.

FIG. 5 is a sequence chart showing a synchronization procedure of an unknown transmission system previously developed by the present applicant. As a procedure for completing the synchronization, a step of designating a synchronization correction target device by simultaneous broadcast, a step of notifying a reference time to a designated communication device and simultaneously storing a transmission time, and a return time from the designated communication device There are a step of storing, a step of calculating the transmission path delay time from the transmission time and the reception time, and a step of notifying the calculated communication path delay time together with the reference time to a designated communication device.
In the step of designating the synchronization correction target device by simultaneous broadcast, the designated communication device that sends the simultaneous broadcast and receives the simultaneous broadcast signal with the second communication device closest to the first communication device as the designated communication device Sets the switch to the operation of returning the received data to the receiving source. In the step of notifying the designated communication device of the reference time and simultaneously storing the transmission time, the first communication device transmits the transmission data including the reference time and simultaneously stores the transmission time. When the transmission data is received by the designated communication device, the transmission data is repeated by the switch inside the communication device. In the step of storing the return time from the designated communication device, the reception time is stored at the same time when the first communication device receives the data repeated from the designated communication device.
In the step of calculating the transmission line delay time from the transmission time and the reception time, the transmission time is subtracted from the reception time to calculate the transmission line delay time between designated communication devices. In the step of notifying the designated communication apparatus together with the reference time of the calculated transmission line delay time, the designated communication apparatus corrects the time based on the transmission line delay time and the reference time included in the received data and synchronizes with the reference time. It was.
Japanese Patent Application No. 2006-005272 (in particular, page 9, FIG. 3)

In the transmission system as shown in FIG. 5, the first communication device performs a plurality of second communications according to a node map (addresses and connection information of a plurality of second communication devices) registered in advance when measuring the transmission line delay. After the synchronization correction target node is designated by simultaneous broadcast to the device, the time correction information of the first communication device is transmitted a plurality of times to the designated node. The first communication device needs to perform this process on a plurality of second communication devices, which is a burden on the CPU.
In addition, it is impossible for the first communication device to recognize that all the second communication devices have completed initialization and are in a simultaneous broadcast standby state in a transmission path to which a plurality of second communication devices are connected. For this reason, if there is a second communication device that has started initialization with a delay, the second communication device cannot recognize the simultaneous broadcast, and the transmission line delay is measured, and the transmission data from the first communication device is repeated. Since the next second communication device may turn back without being able to do this, it is not possible to match the node map, and it is necessary to start over from the beginning. In addition, simultaneous broadcast transmission for each of a plurality of second communication devices has a problem that is a complicated process.
The present invention has been made in view of such problems, and provides a method by which each communication device can be synchronized without complicated processing when the first communication device performs transmission delay measurement. For the purpose.

In order to solve the above problem, the present invention is as follows.
The invention according to claim 1 relates to a synchronous communication method, wherein all devices connected to the transmission path include an in-device reference timer, and the first communication device transmits a reference time in the transmission system as transmission data. In a synchronous communication method in which a plurality of second communication devices other than the first communication device receives the transmission data, corrects a reference timer within the device, and synchronizes with the reference time, the second communication device A relay path for relaying received data from the transmission path without passing through a storage device in the apparatus, and a switch for returning the received data from the relay destination to the reception source on the relay path. Each of the communication devices individually measures the transmission line delay time to the plurality of communication devices, and individually notifies the device of the measurement result and the reference time, the plurality of communication devices and the notified transmission line delay time Equipment base at reference time It is characterized by correcting the timer.
According to a second aspect of the present invention, in the synchronous communication method according to the first aspect, the first communication device notifies a reference time to the designated communication device and simultaneously stores a transmission time; and the designated communication device Storing a return time from the transmission time, calculating a transmission line delay time from the transmission time and the reception time, and notifying the calculated communication line delay time together with a reference time to the designated communication device. , And a synchronization correction of the reference timers of the plurality of second communication devices.
According to a third aspect of the present invention, in the synchronous communication method according to the first aspect, the switch of the plurality of second communication devices returns the received data to the reception source after power-on or initialization. It is a feature.
According to a fourth aspect of the present invention, in the synchronous communication method according to the first aspect, transmission data for transmission line delay measurement transmitted from the first communication device has a storage area for a reference time and a transmission line delay time. The first time stores only the reference time, and the second time and later stores the reference time and the transmission line delay time measured by the previous transmission data.

The invention according to claim 5 relates to a synchronous communication device, and is inserted into two transceivers, a forward communication line and a backward communication line connecting the two transceivers, and each of the forward communication line and the backward communication line. An Rx FIFO, a Tx FIFO inserted between the outgoing communication line and the return communication line on the output side of the Rx FIFO, and a CPU that inputs data from the Rx FIFO and outputs data to the Tx FIFO, and The reference timer is provided inside or outside the apparatus.
The invention according to claim 6 also relates to the synchronous communication device, and is inserted into each of the two transceivers, the forward communication line and the backward communication line connecting the two transceivers, and each of the forward communication line and the backward communication line. RxFIFO, TxFIFO inserted between the forward communication line and the return communication line on the output side of the RxFIFO, a switching switch provided between the RxFIFO and the TxFIFO, respectively, and data from the RxFIFO A CPU that inputs data, outputs data to the TxFIFO, and outputs a switching signal to the loopback switch is provided in the apparatus, and a reference timer is provided inside or outside the apparatus.

According to the first aspect of the present invention, transmission data can be relayed without going through an internal memory. Therefore, even when a transmission line and a device are connected in series, a delay time due to relay can be suppressed, and a highly accurate synchronous operation Can be realized. Further, the plurality of communication apparatuses can calculate the transmission line delay time only by mounting a switch on the relay path.
According to the second aspect of the present invention, the first communication device can centrally manage not only the reference time but also the synchronization of a plurality of communication devices, and can manage the reference time of the entire transmission system.
According to the third aspect of the present invention, since the plurality of communication devices take a procedure of returning the received data to the receiving source after the power is turned on or after initialization, the first communication device does not perform delay measurement. It is possible to perform delay measurement without processing and to synchronize with the reference time promptly.
According to the invention of claim 4, while measuring the transmission line delay time, the plurality of communication devices can correct the time with the reference time and the transmission line delay time stored in the measurement data.
Moreover, according to the invention of Claim 5 and Claim 6, since the synchronous communication method of Claims 1-4 can be performed by using the apparatus of Claim 5 and Claim 6, it is highly accurate. Synchronous operation can be performed quickly.

Hereinafter, specific examples of the method of the present invention will be described with reference to the drawings.
In the following different drawings, those having the same instrument code indicate the same contents, and therefore redundant description is omitted.

FIG. 1 is a block diagram showing a configuration of a communication apparatus to which the method of the present invention is applied.
In FIG. 1, a first communication device 1 and a second communication device 2 are connected by a transmission line 5. The first communication device 1 includes an in-device reference timer 150 for managing the reference time of the transmission system in the CPU 140, and the second communication device 2 is provided in the CPU 240 for synchronizing with the reference time of the transmission system. An in-device reference timer 250 is provided. In this example, the in-device reference timer is mounted inside the CPU, but may be mounted as a dedicated clock outside the CPU.
The first communication device 1 is connected to the transmission line 5 via the transceivers 111 and 112, and absorbs the difference between the transmission data received from the transmission line 5 and the operation clock of the CPU 140 between the transceiver 111 and the CPU 140. The Rx FIFO 121 and the Tx FIFO 131 for absorbing the difference between the transmission data transmitted in accordance with the operation clock of the CPU 140 and the transmission clock are connected. Similarly, the Tx FIFO 132 and the Rx FIFO 122 are connected between the transceiver 112 and the CPU 140. Here, the output end of the Rx FIFO 122 and the input end of the Tx FIFO 121 are connected, and the data received from the transceiver 112 is transferred to the transceiver 111 using the Rx FIFO 122 and the Tx FIFO 121 as a relay path. Similarly, the output end of the Rx FIFO 131 and the Tx FIFO 132 are connected and used as a relay path from the transceiver 111 to the transceiver 112.

The second communication device 2 is connected to the transmission path 5 via the transceivers 211 and 212, and absorbs the difference between the transmission data received from the transmission path 5 and the operation clock of the CPU 240 between the transceiver 211 and the CPU 240. The Rx FIFO 232 and the Tx FIFO 221 for absorbing the difference between the transmission data transmitted in accordance with the operation clock of the CPU 240 and the transmission clock are connected. Similarly, the Rx FIFO 222 and the Tx FIFO 232 are connected between the transceiver 212 and the CPU 240. Here, like the first communication device, in order to relay transmission data received between the two transceivers, the output end of the Rx FIFO 231 and the input end of the Tx FIFO 232, and the output end of the Rx FIFO 222 and the Tx FIFO 221 are respectively connected. .
In addition, the second communication device includes switchers 223 and 233 that disconnect the relay path and return the received transmission data to the reception source. The switch is held in a state where the received transmission data is turned back to the receiving source after the power is turned on or after initialization. When the synchronization delay measurement is completed, the CPU switches the switch to the relay path.
Furthermore, the switcher passes through the same number of FIFOs when the receiver is turned back for synchronous delay measurement and when it is set as a relay path during normal operation.
Although only the second communication device is mounted with the switching device for return on the relay path, it may be mounted on the first communication device to unify the circuit configuration.

FIG. 2 shows an example of a transmission system to which the present invention is applied.
In this example, four communication devices are connected in series to the transmission line. The first communication device 1 manages the reference time, and the second to fourth communication devices have the same block diagram as the second communication device 2 in FIG. Synchronize.
In this example, the first communication device 1 is connected so as to be at the end of the transmission line. However, as described in FIG. 1, the first communication device 1 also has a relay function. You may connect on the way.

FIG. 3 is a sequence chart showing the delay measurement procedure of the present invention.
FIG. 3 also shows the operation flow of each device in addition to the communication sequence.
First, the case where the first communication device 1 performs the synchronization correction of the second communication device 2 will be described. The first communication device 1 transmits the delay measurement data storing the address of the second communication device to be synchronization corrected and the current value of the reference time based on the preset connection information (S122). At the same time, the transmission time is stored (S123).
Thereafter, the first communication device 1 waits for reception of the return data from the second communication device, and stores the reception time when receiving the return data (S124).
Here, the transmission path delay time is calculated from the stored transmission time and reception time (S125), and the delay measurement data storing the current value of the reference time and the calculated transmission path delay time is transmitted to the target device. (S126).
Here, as described in the block diagram of FIG. 1, the same number of stages is used when the switch is set as a relay path during normal operation and when it is turned back to the reception source for synchronous delay measurement. Since the FIFO passes through the FIFO and only absorbs the clock difference, it can be considered that there is no difference in the delay time between the forward path and the backward path. Therefore, if the transmission time is Ts and the reception time is Tr, the transmission line delay time of the transmission line can be calculated by (Tr−Ts) / 2.
FIG. 3 shows a sequence in the case where the first communication device 1 performs the synchronization correction of the third communication device 3, but the description is omitted because it is the same as the above-described procedure. In addition, although the transmission line delay measurement is performed once, the measurement error may be reduced by performing it a plurality of times and averaging.
Next, the operation of the second communication device 2 that receives the synchronization correction will be described.
In the second communication device 2, after the power is turned on or initialized, the switch is in a folded state. In this state, it waits for the reception of the delay measurement data stored with the reference time and the transmission path delay time, and when received, corrects the in-device reference timer 250 with the reference time and transmission path delay time stored in the received data. (S203).
At this time, the received delay measurement data is returned to the first communication device 1 by the switch simultaneously with the reception. As this correction method, there is a method of rewriting the in-device reference timer 250 to a value obtained by adding the reference time and the transmission line delay time.

FIG. 4 is an example of delay measurement data transmitted by the first communication device 1.
The data includes a transmission address 601, a transmission source address 602, a data type 603, and a data length 604, and FCS (Frame Check Sequence) that detects an error in transmission data. In this example, the data type 603 identifies timer correction and correction end. Here, the individual address of the measurement target device is stored in the transmission destination address 601. The transmission path delay time 616 of the delay measurement data stores 0 because the transmission path delay time is not measured at the first transmission, and stores the measurement result measured by the first transmission at the second transmission. To do.

In this way, since the two transceivers have a relay path connected by RxFIFO and TxFIFO that only absorb the clock difference, all the communication apparatuses even in the transmission system in which the transmission path and the communication apparatus are connected in series However, it is possible to perform a highly accurate synchronous operation.
Further, since only a switch between RxFIFO and TxFIFO needs to be mounted on a plurality of communication devices synchronized with the reference time, it can be realized with a simple circuit at low cost.

It is a block diagram which shows the structure of the communication apparatus to which the method of this invention is applied. It is an example of the transmission system to which this invention was applied. It is a sequence chart which shows the delay measurement procedure of this invention. It is a format of transmission data for delay measurement of the present invention. It is a sequence chart which shows the synchronous procedure of the transmission system which the present applicant developed previously.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st communication apparatus 2 2nd communication apparatus 3 3rd communication apparatus 4 4th communication apparatus 5 Transmission path 111,112,211,212 Transceiver 121,132,221,232 TxFIFO
122, 131, 222, 231 Rx FIFO
140, 240 CPU
150, 250 In-device reference timers 223, 233 Switcher 601 Transmission destination address 602 Transmission source address 603 Type 604 Data length 605 Target device address 606 FCS
615 Current value of reference time 616 Transmission line delay time

Claims (6)

All devices connected to the transmission line have an in-device reference timer, the reference time in the transmission system is transmitted as transmission data by the first communication device, and a plurality of second communications other than the first communication device. In the synchronous communication method in which the device receives the transmission data, corrects the reference timer in the apparatus, and synchronizes with the reference time,
The second communication device includes a relay path that relays the received data from the transmission path without passing through the storage device in the apparatus,
A switch is provided on the relay path to return the received data from the relay destination to the receiver,
The first communication device individually measures transmission line delay times to the plurality of communication devices, individually notifies the device of the measurement result and the reference time, and the plurality of communication devices are notified of the transmission lines. A synchronous communication method comprising correcting an in-device reference timer with a delay time and a reference time.   The first communication device notifies the designated communication device of a reference time and simultaneously stores a transmission time, stores a return time from the designated communication device, and includes the transmission time and the reception time. A step of calculating a transmission line delay time and a step of notifying the designated communication device together with the calculated transmission line delay time together with a reference time, the synchronization correction of the reference timers in the plurality of second communication devices. The synchronous communication method according to claim 1, wherein the synchronous communication method is performed.   2. The synchronous communication method according to claim 1, wherein the switch of the plurality of second communication devices wraps received data back to a reception source after power-on or initialization.   Transmission data for transmission line delay measurement transmitted from the first communication device has a storage area for a reference time and a transmission line delay time, the first time stores only the reference time, and the second time and thereafter the reference time and the previous time. 2. The synchronous communication method according to claim 1, wherein the transmission path delay time measured by the transmission data is stored.   Two transceivers, an outbound communication line and an inbound communication line connecting the two transceivers, an RxFIFO inserted into each of the outbound communication line and the inbound communication line, and each outbound communication on the output side of the RxFIFO A TxFIFO inserted into the line and the return communication line, and a CPU that inputs data from the RxFIFO and outputs data to the TxFIFO, and a reference timer is provided inside or outside the apparatus. A characteristic synchronous communication device.   Two transceivers, an outbound communication line and an inbound communication line connecting the two transceivers, an RxFIFO inserted into each of the outbound communication line and the inbound communication line, and each outbound communication on the output side of the RxFIFO A TxFIFO inserted between the TxFIFO and the RxFIFO, a turn-back switch provided between the TxFIFO and the RxFIFO, respectively, input data from the RxFIFO, output data to the TxFIFO, and return A synchronous communication device comprising: a CPU for outputting a switching signal to a switching device for use in the device; and a reference timer provided in the device or outside the device.

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