JPH0435934B2 - - Google Patents

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention relates to a data transmission method, and in particular, the present invention relates to a data transmission method, and in particular, the present invention relates to a data transmission system that uses a token passing bus to transmit data (for example, voltage, current, etc.) at multiple points distant from each other. This invention relates to a signal synchronization method for simultaneously sampling instantaneous values such as

(Prior art) Regarding a method for controlling transmission path usage allocation when control stations scattered at multiple locations use a common transmission cable in a time-sharing manner to transmit and receive data, IEEE
(Institute of Electrical and Electronics Engineers of the United States) and ISO (International Organization for Standardization) are currently working on various standardization efforts.
In particular, the token passing bus method promoted by the IEEE802.4 committee and ISO DP8824 is real-time, meaning that transmission is always possible within a certain fixed time, so it is suitable for controlling factories, etc. It is beginning to be adopted as a standard for transmission equipment.

The outline of this token passing bus method is explained in the second section.
This will be explained using figures. The stations ₁₁ to _1o that make up the network are connected to branching devices ₃₁ to _3o called taps.
It is connected to the coaxial cable 2 via.

In the token passing bus system, transmission rights called tokens are passed in order between stations joining the network, preventing multiple stations from transmitting at the same time. Tokens are passed in order from the station with the largest station address to the station with the smallest address, and each station remembers the successor station to which it should pass the token, and the tokens are passed forming a logical ring. . The token passing bus system has the following functions in order to maintain this logical ring even when a station leaves due to the joining of a new station or failure of a joining station, and loss of tokens due to noise. In other words, there is a new station invitation function that invites new stations to join the logical ring at approximately regular intervals, and a token reissue function that allows the previous token holding station to reissue tokens when tokens are temporarily lost due to noise, etc. It has an issuing function and a succeeding station exclusion function that passes a token to a further succeeding station when a succeeding station fails and excludes the failed station from the logical ring.

To perform signal synchronization using the token passing bus method, a specific station is set as the master station, and stations other than the master station (slave stations) synchronize with the master station using data frames sent synchronously by the master station. One possible method is to synchronize.

That is, the main station 1 ₁ sends the main synchronization signal S ₁ with a period T
If the data frame D ₁ of the master station 1 ₁ is transmitted in synchronization with the main synchronization signal S ₁ , the slave stations 1 ₂ to 1 _o will calculate backward from the reception time of the data frame D 1 and transmit the data frame D ₁ of the master station 1 1 in synchronization with the main synchronization signal S ₁ . It becomes possible to know the time of occurrence, and it becomes possible to synchronize the signals of all stations participating in the network.

Data frame for synchronization sent by master station 1 ₁
Hereinafter, D ₁ will be referred to as a synchronous data frame.

However, as mentioned above, the token passing bus method requires new stations to solicit, join or leave for the logical ring maintenance function, token passing retries, and fluctuations in the data frame transmission time of each station, etc., resulting in token circulation time. changes. Therefore, the main synchronization signal S ₁
In order to transmit the synchronous data frame D1 at a constant period in synchronization with the data frame _D1 , a new transmission time adjustment means is required.

In the token passing bus method, if the master station postpones transmission until the transmission start time (synchronization timing) of synchronous data frame D ₁ , the bus monitoring algorithm of the preceding station that passed the token to the master station will treat it as a token passing failure. The preceding station then takes steps to reissue the token. Furthermore, if the master station ₁ postpones transmission for a period of time that is considered to be no response,
There is a problem in that the main station ₁₁ is removed from the logical ring as a failure. Therefore, in order to solve the above problem, until the transmission start time of synchronous data frame D ₁ ,
A possible method is to adjust the transmission time of the synchronous data frame _D1 by transmitting a dummy empty data frame and changing the length of this empty data frame according to the time when the token arrives at the main station.

(Problem to be solved by the invention) However, in the above method, the length of the empty data frame is calculated and the frame is constructed to create a synchronous data frame.
The processing time required to transmit _D1 prior to the start of transmission is limited, and the amount of data that can be transmitted and the transmission speed of the network are restricted. Further, when receiving a synchronization data frame transmitted by the master station and performing phase synchronization, there is a problem in that the fluctuation of the synchronization signal of the slave station becomes large.

The present invention uses a token passing bus method to generate a synchronous data frame synchronized with the main synchronization signal _S1 .
A transmission time adjustment method in which the main station transmits D ₁ at regular intervals with plenty of time, token retransmission due to stochastically generated noise, and synchronized data frame transmission time fluctuations due to new stations joining or leaving. The transmission time fluctuation of the synchronized data frame of the main station due to the time fluctuation required for data frame transmission processing of each station is
It is an object of the present invention to provide a new signal synchronization method that does not reduce signal synchronization accuracy in a slave station synchronized with a master station.

[Structure of the invention]

(Means for Solving the Problems) The gist of the present invention is to adjust the transmission completion time of the signal synchronization data frame, that is, the synchronization data frame, in the main station of signal synchronization. synchronous data frame, and changes the length of the empty data frame according to the time difference between the transmission completion time of the synchronous data frame and the main synchronous signal, making it possible to transmit a synchronous data frame synchronized with the main synchronous signal. It is.

That is, the station that becomes the main station of synchronization is equipped with a means for generating a main synchronization signal, and uses the above-mentioned means to adjust the transmission completion time of the synchronization data frame transmitted by the own station.
transmitting an empty data frame prior to transmitting the synchronous data frame, calculating the length of the empty data frame based on the time difference between the transmission completion time of the synchronous data frame and the main synchronizing signal, and configuring the frame;
Next, until the master station receives the token frame, the empty data frame is added to the transmission queue prior to the transmission queue of the synchronous data frame, and the empty data frame is followed by synchronous data synchronized with the main synchronization signal. Enable frame transmission. On the other hand, the slave station performs signal synchronization following the master station by detecting the completion of reception of the synchronization data frame.

In other words, if the slave station is equipped with a station phase synchronization circuit that generates a station synchronization control signal capable of phase synchronization control, and there is a time difference between the reception completion time of the synchronization data frame and the station synchronization control signal, the reception of the synchronization data frame is completed. Rather than correcting the phase of the local phase synchronization circuit as it is at the time, signal synchronization is performed by adjusting the phase within a certain range to the reception completion time of the synchronization data frame and making it follow it.

Furthermore, if the time difference between the transmission completion time of the synchronization data frame and the main synchronization signal is outside a certain range, the main station sets a transmission synchronization failure bit in the synchronization data frame to indicate this, and receives and detects this. When a transmission synchronization failure occurs in the master station, the slave station stops the phase correction of the station phase synchronization circuit and uses the station synchronization control signal of the station phase synchronization circuit as the synchronization signal for the slave station. This allows signal synchronization to be maintained.

(Operation) When the main station detects the arrival of a token, an empty data frame is sent before the synchronous data frame,
A synchronous data frame is then transmitted. The main station calculates the frame length of the empty data frame based on the time difference between the main synchronization signal and the transmission completion time of the synchronized data frame, and constructs the empty data frame.
By adding the empty data frame and the synchronous data frame to the transmission queue until the next token is received, the current time difference, that is, the error in the synchronous signal transmission, is corrected and the next synchronous data frame is , transmitted in synchronization with the main synchronization signal. The slave station receives the synchronization data frame, corrects the phase of the station phase synchronization circuit, and synchronizes the synchronization signal of its own station. In this case, fluctuations in the synchronized data frame transmission completion time of the main station are largely due to transient and stochastic factors, and the phase correction of the station phase synchronization circuit is performed to match the synchronized data frame reception completion time. When this is done, fluctuations in the synchronized data frame transmission completion time become slave station and signal synchronization fluctuations.
Therefore, if there is a time difference between the synchronization data frame reception completion time and the station synchronization signal, phase synchronization correction is performed within a certain phase range to achieve tracking synchronization with the synchronization data frame reception completion time of the main station. Also, when the synchronization data frame is poorly synchronized due to a delay in token arrival time or other reasons, the main station sets a transmission synchronization failure bit in the synchronization data frame and transmits it.
When the slave station receives and detects the synchronization failure bit, phase correction of the station phase synchronization circuit is prohibited, and the station synchronization signal of the slave station is maintained stably.

(Example) An example of the present invention will be described below using FIGS. 1 to 6. FIG _. 1 is for explaining a method of transmitting a synchronized data frame of a master station using the signal synchronization method of the present invention. In the token passing bus of _FIG.
~1 Let _o be the subordinate station.

FIG. 3 shows an example of a block configuration having both main station and slave station functions. The master station and slave station will be explained in detail below.

a Detailed description of the main station The main station ₁₁ has a signal source of the main synchronization signal _S1 shown in FIG. Figure 4 shows the status of the token passing bus where signal synchronization is performed, and shows the _state of the token passing bus where signal synchronization is performed.
D _o represents data frames transmitted by stations 1 ₁ to 1 _o , respectively, and T ₁ to T _o represent tokens.

On the other hand, in D _s , the main station 1 ₁ adjusts the time,
This is an empty data frame to send. FIG. 5 is an enlarged view of the transmitted signal portion of the main station. When the main station ₁₁ detects the token T _o , it transmits an empty data frame D _s before transmitting the synchronous data frame D ₁ . In this case, when the token disappears temporarily due to noise, etc., or when any station solicits a new station, the arrival of the token to the main station ₁₁ is delayed due to the retransmitted token or solicitation frame.
When a station leaves the station, the token arrival to the main station ₁₁ is accelerated.

Therefore, the length of the empty data frame D _s is such that the transmission completion time of the synchronous data frame D ₁ is the main synchronous signal.
It is necessary to change the transmission time _ts according to the time when the token arrives at _{the main station 11 so} as to be synchronized with S1. Here, the preconditions are the sum of the gap time t _f between one frame, the sum of the token transmission times t _T of all stations, and the maximum data frame transmission time of all stations.
The sum T _TRO of the sums of t _Dnax is smaller than the synchronization signal synchronization T, and the difference between the two T - T _TRO is the gap time between frames t _f and the minimum length of the empty data frame D _s
Suppose that it is selected to be larger than the sum of t _Snio .
The above-mentioned gap time t _f is the sum of the transmission delay between stations and the station delay occurring in signal processing at the station.

However, in the token passing bus, the empty data frame length _ts cannot be changed in accordance with the token arrival time.
First, stations are generally not equipped with the ability to know when a token arrives. Second, main station 1
₁ starts transmitting the empty data frame D _s as soon as it recognizes the arrival of a token, so there is no time to calculate the empty data frame length t _s .

Therefore, to solve the first problem, for example, as shown in FIG. 3, the main station ₁₁ is provided with means for detecting the transmission completion time of the synchronous data frame _D1 . That is, the output signal _Tx1 from the token passing bus control circuit (hereinafter abbreviated as TBC) 12 to the modem 11 is branched and input to the transmission/reception completion detection circuit 16, and the transmission/reception completion detection circuit 16 detects the synchronous data frame _D1 . A transmission completion pulse Q _s is generated at the time of transmission completion.
This pulse Q _s causes the registered timer 17 to
The transmission completion time is stored in the register, and an interrupt is requested to the token passing bus processor 13 by _Qs to read the transmission completion time. The timer 17 with a register is reset to '0' (or set to the maximum value) by the main synchronization signal _S1 of the station synchronization signal generation circuit 20, and after that, it is connected to an up (or down) counter that counts the time clock and this counted value. Consists of registers for storage. Therefore, the time difference between the synchronization data frame transmission completion time and the main synchronization signal _S1 can be detected from the count value of the register timer 17, and the talk arrival time can be indirectly known.

Next, for the second problem, the empty data frame length to be transmitted when receiving the next token is calculated based on the time difference detected this time, and the next synchronous data frame transmission completion time is determined by the main synchronous signal.
Correct to match S ₁ . Therefore, main station 1
₁ can be added to the transmission queue that constitutes an empty data frame with sufficient time, and it becomes possible to transmit the synchronized data frame D ₁ synchronized with the main synchronization signal S ₁ .

In addition, the synchronization data frame _D1 transmitted by the main station ₁₁ includes bits related to transmission synchronization,
When the above time difference exceeds the allowable value, a transmission synchronization failure bit is set in the synchronization data frame _D1 to be transmitted the next time a token arrives and added to the transmission queue.

The frame formats of the data frames D ₁ -D _o and the empty data frame D _s are as shown in FIG. 6 and conform to the IEEE802.4 token passing bus system.

b. Detailed explanation of the stations serving as vertical stations The vertical stations ₁₂ to _1o have means for detecting the completion of reception of the synchronization data frame _D1 transmitted by the main station ₁₁ and synchronizing the station synchronization signals of their own stations. ing. That is, in the configuration shown in FIG. 3, the token passing path control circuit 12 generates an interrupt request IRQ upon completion of receiving the data frame D, and the token passing bus processor 13 immediately processes the data upon receiving this interrupt request. Determine frame D and detect completion of reception of synchronous data frame _D1 . Immediately upon detecting the synchronization data frame _D1 , a reception synchronization pulse Q _R is generated from the output port 21.

The received synchronization pulse Q _R is compared with the station synchronization signal S output from the station synchronization signal generator 20 by a phase comparator 22, and a signal corresponding to the phase difference is generated.
DPH is output, and the phase of the station synchronization signal S is adjusted within a certain range based on this signal DPH. That is, rather than matching the phase of the station synchronization signal S with the phase of the received synchronization pulse Q _R , the phase of the station synchronization signal S is finely adjusted in the direction of decreasing the phase difference by determining whether the phase is advanced or delayed. As a result, the station synchronization signal S of the slave station ultimately becomes the received synchronization pulse.
For Q _R , the judgment processing time of the token passing bus processor 13, the inter-station transmission delay time,
It is matched at an early time equal to the sum of the station delay times, and is matched with the main synchronization signal _S1 , and is synchronized. In this way, the phase comparator 22 and the station synchronization signal generator 2
0 forms a local phase synchronization circuit.

In addition, the slave station determines the synchronization data frame D ₁ and also detects and stores the state of the transmission synchronization failure bit. If the synchronization failure occurs a specified number of times in a row, output to the output port 21 is prohibited and the synchronization signal generator 20 The synchronization signal S is maintained at the phase before the synchronization failure occurred.

The transmission synchronization fluctuation error of the synchronized data frame transmitted by the master station is usually transient, and it is necessary to prevent the transmission synchronization fluctuation error of the synchronized data frame that occurs stochastically from directly appearing as signal synchronization fluctuation within the slave station. ing.

In this way, the stability of the oscillation circuit of the slave station is taken into account so that the signal synchronization will be maintained for a certain period of time even if the master station is in an abnormal state, and the backup of the master station will be maintained in the signal synchronized state. It is effective in doing so.

The transmission line of the present invention is not limited to the bus system as shown in FIG. 2, but may also be constructed using optical fiber cables 5 ₁ to 5 _o and optical star coupler 4 as shown in FIG. 7, for example. good.

Furthermore, although the above embodiment describes the IEEE802.4 token passing bus, the present invention can also be applied to networks having similar communication protocols.

〔Effect of the invention〕

Networks with IEEE802.4 token passing bus or similar communication protocols do not originally have a signal synchronization function, but by using the signal synchronization method of the present invention, the function originally provided can be improved. It is equipped with a signal synchronization function without sacrificing the characteristics (features such as real-time performance, self-recovery, scalability, etc.), and can be used to simultaneously obtain data (instantaneous values of voltage, current, etc.) at multiple points over the network. This becomes effective for sampling signal synchronization, etc., making it possible to further expand the range of uses.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of a method for transmitting synchronous data frames using the signal synchronization method of the present invention, FIG. 2 is a block diagram of a bus network using coaxial cables, and FIG. Figure 4 is a block diagram showing an example of the circuit configuration of a station that has both master station and slave station functions in this system. Fig. 4 is an enlarged view of the main station transmission signal part, Fig. 6 is a data frame structure diagram in the IEEE802.4 token passing bus, and Fig. 7 is an enlarged view of the main station transmission signal part in Fig. 4. FIG. 1 is a configuration diagram showing an example of a network. _S1 ...Main synchronization signal, _D1 ...Synchronization data frame, _Ds ...Empty data frame, _T1 ~T _o ...Token, 1 ₁ ~ _1o ...Token passing bus station, 2... Coaxial cable, 3 ₁ to 3 _o ...Tap (brancher), 4... Optical star coupler, 5 ₁ to 5 _o ...
Optical fiber cable (double fiber), 11
...Modem (modulation/demodulation circuit), 12...Token passing bus control circuit (TBC), 13...Token passing bus processor, 14...Memory, 15...Interface with upper position, 16
... Transmission/reception completion detection circuit, 17... Timer with register, 20... Synchronization signal generation circuit, 21... Output port, 22... Phase comparator.

Claims (1)

[Scope of Claims] 1. In a signal synchronization method using an IEEE802.4 token passing bus or a network having a communication protocol similar to this, a station that becomes the main synchronization station has a means for generating a main synchronization signal. In order to adjust the transmission completion time of the synchronous data frame transmitted by the own station, an empty data frame is transmitted prior to the transmission of the synchronous data frame, and the empty data frame is set at the transmission completion time of the synchronous data frame. The length of the synchronous data frame is calculated based on the time difference with the main synchronous signal, the frame is constructed, and the empty data frame is added to the transmission queue before the synchronous frame transmission queue to be transmitted next. A transmission completion time is transmitted in synchronization with the main synchronization signal, and a station that becomes a synchronized slave station synchronizes its own station synchronization signal with the main synchronization signal by detecting the completion of reception of the synchronization data frame. Characteristic signal synchronization method. 2. Each of the main station and the slave station follows a predetermined signal phase to achieve phase synchronization, and when there is a phase difference from the phase to be synchronized, outputs a station synchronization signal that achieves phase synchronization within a certain phase range. A station phase synchronization means is provided, in the case of the master station, synchronizes the station synchronization signal with the main synchronization signal without phase difference, and in the case of the slave station, synchronizes the reception completion time of the synchronization data frame with the station synchronization signal. The signal synchronization method according to claim 1, wherein the phase of the station synchronization signal is corrected within a certain phase range according to the time difference to synchronize with the main synchronization signal. 3. When the time difference between the transmission completion time of the synchronization data frame and the main synchronization signal exceeds an allowable range, or when the main synchronization signal disappears due to an abnormality, the main station converts the transmission synchronization failure bit into the synchronization data frame. Claim 2 is characterized in that when the slave station that receives the transmitted signal is set at a specific position and receives the transmitted synchronization defective bit, it prohibits the phase correction of the station phase synchronization circuit. signal synchronization method.