JPH1141263A - Ring type network system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the transmission efficiency of a network by changing the number or stages or a buffer according to the performance and state of the system that uses the network. SOLUTION: A master station of a network system transmits the information in an initialization processing mode to set the number of stages of a frequency compensation buffer of every slave station based on the performance, state, etc., of the system. The slave station extracts the specific data and transmission clocks from those received data and stores them in a frequency deviation compensation buffer 2. A buffer stage number setting part 4 calculates the number of stages of the buffer 2 to be set and decides the number of these stages with control based on the largest length, type, state, etc., of the frame that is sent from the master station and used in the system. Meanwhile, a data transmitting part 3 controls the timing to start to take the data out of the buffer 2. Thus, the optimum number of stages of the buffer 2 is decided to the network system and it's possible to prevent the deterioration of transmission efficiency that is caused by the excessive transmission delay.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to compensation for frequency deviation in a ring network.

[0002]

2. Description of the Related Art One of the shapes of a network is IE.
There is a ring (loop) network represented by a token ring network defined in EE802.5.

In a ring network, each station is physically arranged on a ring-shaped transmission line, and the station receives a frame flowing in a certain direction on the transmission line from an upstream station. If the address of the received frame is not its own, the receiving station regenerates the frame and sends it to the next downstream station. In this way, in a ring network, each station sequentially relays frames,
Data communication is performed by circulating in the transmission path.

In this ring type network, when receiving a data frame transmitted from an upstream station, the receiving station samples and captures data with a sampling clock generated by its own clock, shapes the waveform, and then shapes the waveform. The data is transmitted to the downstream station using the transmission clock.

As described above, in the ring network, each station extracts data from a data frame having the clock timing of the upstream station at the timing of the clock of the receiving station. Therefore, since the transmission speed of the network is constant, all the clocks of each station must have the same frequency.

However, the clock of each station is 50 to 100 pp with respect to the specified frequency depending on the temperature environment and the like.
It is common to have a frequency variation (frequency deviation) on the order of m (parts per million).

Therefore, even if all stations use the same specified frequency clock for data communication, the clock used by one station in the network and the clock used by another station are actually different. It is possible that the frequencies are different. Therefore, even when operating at the same timing when transferring the first bit of the transmission frame during frame relay,
Due to the frequency deviation, a deviation gradually occurs in the timing between transmission and reception. If the magnitude of this deviation exceeds the one-bit length of the data frame, unnecessary addition (overrun) or loss (underrun) occurs in the frame data.

As a method for solving this problem, a method of providing a deviation compensating buffer using a plurality of 1-bit registers, buffering data frames, and compensating for a clock frequency deviation between transmission and reception is generally used.

FIG. 5 is a block diagram showing a data transfer process at each station using a buffer for deviation compensation.
In FIG. 5, a data receiving unit 101 receives data from an upstream station of a ring network. The received data includes a clock component such as a Manchester code. The data receiving unit 101 samples the received data with a clock having a frequency several times the transmission clock, extracts the data and the transmission clock, and stores the data and the transmission clock in the deviation compensation buffer 102. Store. The deviation compensating buffer 102 is a multi-stage 1-bit buffer composed of a plurality of 1-bit registers. The data transmission unit 103 extracts data from the buffer 102, uses the data to perform Manchester encoding using a transmission clock, forms a frame, and sends the frame to a downstream station in the network.

FIG. 6 is a diagram for explaining a method of compensating for a frequency deviation by the deviation compensating buffer 102. In FIG. 6, a buffer having a capacity of 5 bits is used to deal with overrun / underrun of up to 2 bits each.

The frame data received from the network is stored in the buffer 102 by sequentially storing the received data in the second, third,..., Stages from the first stage at the speed of the transmission clock from the upstream station. Next to the first row, the data is cyclically stored again to the first row.

On the other hand, when data is taken out from the buffer 102, if the data storage side stores the data in the third-stage buffer, the data transmission unit 103 sends the data to the FIFO (Firs
t InFirst Out) method, the data is taken out from the first stage of the buffer, from the first stage to the third stage, and so on, in the order of storage, and is taken out again from the first stage after the fifth stage.

With this arrangement, if a clock shift becomes longer than one bit in a normal case, a loss of a bit or the like may occur. By providing a buffer as shown in FIG. The frequency deviation can be compensated for the overrun / underrun of up to 2 bits, so that long data can be continuously transmitted.

[0014]

The deviation due to the frequency deviation at the time of data transmission becomes larger than the size of the transmission frame. Therefore, in the method using the buffer for compensating the frequency deviation of the clock, the number of stages of the buffer is determined so that the frame having the maximum data length among the frames flowing through the network can be transmitted. That is,
The number of stages in the buffer is determined based on the data length (maximum data length) of the longest frame transmitted on the network, assuming that the maximum frequency deviation is constant. This maximum data length is the largest among frames used by various systems using the network.

By the way, each time a transmitted frame passes through a buffer for compensating for clock frequency deviation of each station, a transmission delay occurs, and this delay increases as the number of buffers in each station increases. For example, as shown in FIG. 6, when the number of stages of the buffer is determined corresponding to a shift of a maximum of 2 bits, the transmission frame is delayed by two clocks for each station by the buffer. Thus, as the number of stages of the buffer increases, the transmission delay also increases.

The larger the data length of the network, the larger the number of buffer stages in each station. The larger the number of buffer stages, the greater the delay occurring at each station, and the worse the network transmission efficiency. In particular, even in a system that does not require a data length much longer than the maximum data length of the network, the number of stages of the buffer is the number of stages defined by the network, and the transmission efficiency is reduced more than necessary.

The present invention has been made in view of the above points, and has been made in connection networks of process input / output devices.
In a ring network used as one form of a small-scale network, a network system and a method capable of improving the transmission efficiency of a network by making the number of stages of a buffer variable by a system using the network The purpose is to provide.

[0018]

The network system according to the present invention relates to a ring network system having one master station and one or more slave stations. The master station has maximum length notifying means, and the slave station has buffer means and stage number setting means.

The maximum length notifying means generates and transmits a frame including information based on the maximum length of the frame used by the system using the ring network. The buffer means buffers received data from the network.

The number-of-stages setting means sets the number of stages of the buffer means based on the value of the maximum length of the frame based on the notification frame. In another embodiment of the present invention, a station in the ring network has a frame length measuring unit.

The frame length measuring means measures the length of a frame passing through the own station. And the number-of-stages setting means,
The number of stages of the buffer means is set based on the longest frame length measured by the frame length measuring means within a certain period.

According to the present invention, each station can transmit its own buffer means based on information from the master station based on the maximum length of a frame used by the system using the above-mentioned ring type network, or based on the measurement result by the frame length measuring means. Is set, the delay of the transmission frame flowing through the network by the buffer means can be reduced.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION As one embodiment of the present invention, several stations to about several hundreds used for FA (Factory Automation), a network length of several tens to several hundreds meters,
A case where the present invention is applied to a LAN having a transmission frequency of about several M to several tens MHz will be described.

FIG. 1 is a diagram for explaining a schematic diagram of a ring network system according to the first embodiment. FIG.
In the configurations 2 and 2, an arbitrary number of stations a, b,... M are connected on the ring network 10, of which the station a is the master station for managing the network, and the stations b to m are the slave stations. I do. Arrows on the ring connection type network 10 indicate directions in which frame data flows.
The slave station closest to the master station a on the network 10 is the station b, and the next station is the station c,. . . , The most downstream station is station m. Also, since the network 10 is a ring network, the master station a receives a frame from the slave station m at the most downstream.

Each of the stations a to m has a frequency deviation compensating buffer in which the number of stages described later can be changed. At the time of starting the network, each station sets the number of stages of the buffer to a value based on the data length (maximum data length) of the longest frame transmitted on the network as in the conventional case.

When the network system is started, the master station a performs initialization processing of the network system, for example, setting of network status such as setting / collection of a station number, and information collection.

As one of the initialization processes, the master station transmits, to the frame, information for setting the numerical values of the frequency compensation buffers of the stations b to m based on the performance and state of the system using the network. 11 and transmitted to the network.

The information of the frame 11 includes, for example, information indicating the maximum length of a frame used by a system using a network, or information indicating the type and state of the system. In this case, a step value is obtained for each station using the information in the frame 11. Alternatively, it is also possible to transmit the numerical value of the stage determined by the station a as the frame 11, and each station can set it as the number of stages of its own buffer.

Upon receiving this frame 11, the stations b to m take out the above information, set the number of stages of their own frequency deviation compensating buffer based on the information, and transmit the frame 11 to the downstream stations.

The frame 11 makes a round in the network 10 and the station a receives it when the setting of the number of buffers in the stations b to m is completed. Thus, the station a recognizes that the setting of the number of stages of the buffer has been completed at the stations b to m in the network.

FIG. 2 is a block diagram of the first embodiment focusing on a buffer for deviation compensation in each station. In FIG. 2, a data receiving unit 1 receives data from an upstream station of a ring network, samples the received data with a clock having a frequency several times the transmission clock of the network 10, and extracts the data and the transmission clock. Then, it is stored in the deviation compensation buffer 2. Further, the data transmitting section 3 takes out the data from the frequency deviation compensating buffer 2, regenerates the frame by its own clock, and sends it to the downstream station. The data receiving unit 1 and the data transmitting unit 3 are obtained by adding a function to a buffer stage number setting unit 4 described later to the data receiving unit 101 and the data transmitting unit 103 in FIG.

The frequency deviation compensating buffer 2 is a multi-stage 1-bit buffer composed of a plurality of 1-bit registers. The buffer 2 compensates for the frequency deviation in the longest data length (maximum data length) frame transmitted on the network. Assuming that the size of the buffer and the number of necessary buffer stages obtained based on the maximum data length are n, the buffer has a capacity of 2n + 1 or more. The storage format of the data in the buffer 2 is a cyclic format in which the data is sequentially stored from the first row, the next row below the bottom row is a cyclic format that returns to the first row, and the data is extracted from the FIFO.
Format.

The buffer stage number setting unit 4 determines the stage value of the frequency deviation compensating buffer 2 based on the information from the station a, and controls the buffer 2 and the data transmission unit 3. The buffer stage number setting unit 4 uses, for example, when the information given from the station a in the frame 11 is the stage value itself to be set in the buffer, the value is used as the value of the frame used in the system using the network. In the case of information indicating the maximum length, system type, status, or the like, the number of stages to be set is calculated using the information, or the information is obtained from a value obtained in advance and stored in the buffer stage number setting unit 4. To decode and select, and based on that, buffer 2
And the data transmission unit 3.

When the data receiving unit 1 receives the frame 11 from the station a from the network 10, it notifies the buffer stage number setting unit 4 of the information in the frame 11. In response to this, the buffer stage number setting unit 4 determines the value of the stage number of the frequency deviation compensating buffer 2 from the values calculated in advance using the information or by decoding the information. Thereafter, the buffer stage number setting unit 4 controls the buffer 2 and the data transmission unit 3 so that the frequency deviation compensating buffer 2 functions as a buffer of this stage number.

FIG. 3 is a diagram for explaining the setting of the number of stages in the buffer 2 for frequency deviation compensation. The number of stages of the frequency deviation compensating buffer 2 of each station is initially set to the number of stages corresponding to the data length (maximum data length) of the longest frame transmitted on the network. When the maximum data length is transmitted, there is a possibility that a maximum n-bit frequency deviation will occur, and the number of stages in the buffer 2 is n.

FIG. 3A is a diagram showing the setting of the number of stages in the buffer 2 in the initial state. Since this buffer 2 is for compensating the frequency deviation, the buffer 2
Does not indicate the capacity of the buffer 2 itself,
It indicates how many stages data is stored in the buffer 2 by the data receiving unit 1 before the data transmitting unit 3 retrieves data from the buffer 2. As shown in FIG. 3A, when data is stored up to the n-th stage of the buffer 2 by the data receiving unit 1, the data transmitting unit 3 starts to fetch the stored data. Underflow / overflow can be dealt with.

Next, regarding the number of stages of the frequency deviation compensating buffer 2, the frame a is transmitted from the station a, and in response to this, the buffer stage number setting unit 4 determines the value of the number of stages of the frequency deviation compensating buffer 2. If this value is k, k ≦ n.

FIG. 3B shows the state after the number of stages of the buffer 2 has been set by the buffer stage number setting unit 4. When receiving the information in the frame 11 from the data receiving unit 1, the buffer stage number setting unit 4 determines the stage value k of the frequency deviation compensation buffer 2 based on the information. Thereafter, the data buffer stage number setting unit 4 controls the buffer 2 and the data transmission unit 3, and determines the timing at which the data transmission unit 3 retrieves stored data from the buffer 2 and the timing at which the data reception unit 1 transmits data to the n stages of the buffer 2. The time is changed from the time when the data is stored up to the eye to the time when the data is stored up to the kth stage.

Thus, the buffer 2 operates as a k-stage frequency deviation compensation buffer capable of coping with underflow / overflow of up to k bits.
The transmission frame is transmitted by the buffer 2 as shown in FIG.
In FIG. 3A, a delay corresponding to n clocks occurs, but in FIG. 3B, a delay corresponding to k clocks occurs, and the delay due to the frequency deviation compensating buffer 2 is minimized.

As described above, in the first embodiment, the buffer stage number setting units 4 of the stations b to m control the frequency deviation compensation buffer 2 and the data transmission unit 3 based on the information from the master station a. The number of stages of the buffer 2 is changed to a value optimized for a system using a network by controlling the timing at which the data transmission unit 3 starts to fetch stored data. As a result, it is possible to prevent a reduction in transmission efficiency due to an unnecessary transmission delay in the buffer 2.

Next, a second embodiment will be described. In the second embodiment, the number of buffers is not determined by the information from the master station as in the first embodiment.
Each station is provided with a circuit for measuring the data length of a transmission frame passing through its own station, that is, a transmission frame flowing on a ring network, and each station uses its measurement result for a fixed period to determine the number of stages of its own frequency deviation compensation buffer. Set.

In the second embodiment, first, each station initially sets the number of buffer stages for frequency deviation compensation to the data length (maximum data length) of the longest frame transmitted over the network as in the first embodiment. It is set to a value n based on this.

After the network system starts up,
Each station measures the length of the transmission frame passing through its own station for a certain period of time, and stores the maximum value of the length of the frame passing through its own station during that time.

FIG. 4 is a schematic block diagram for realizing the second embodiment. As a configuration for determining the maximum value of the length of the passing frame and storing the maximum value,
General method such as storing the maximum value of the previous measurement value in a register or the like, comparing the previous value with the current measurement value when a new measurement is completed, and holding the larger value as the maximum value in the register It can be realized by.

In FIG. 4, first, the data receiving section 21 samples a frame received from the ring network 24, and then stores the data as received data in the frequency deviation compensating buffer 22 at the timing of the received frame storage signal 30. Further, the data receiving section 26 raises the frame start / end notification signal 29 and notifies the frame data length counter circuit 25 of the start of the frame. In response, the frame data length counter circuit 25 outputs the frame storage signal 3
Start counting 0.

When the reception of one frame is completed, the data receiving section 23 lowers the frame start / end notification signal 29 and notifies the frame data length counter circuit 25 of it.
In response to this, the frame data length counter circuit 25 finishes counting the frame length based on the frame storage signal 30, and uses the count value as a measurement result as a frame comparison circuit 27.
Output to The frame comparison circuit 27 compares the frame length 33 of the frame received this time with the maximum length 34 of the frame measured up to the previous time stored in the frame maximum data length storage register 26, and determines the larger value 35. It is stored in the register 26.

When a period in which these operations are repeated for a predetermined period and the measurement is completed is completed, the frame length stored in the frame maximum data length storage register 26 is set as a maximum frame length value 36 of the frame transmitted through the network 24 and the buffer is used. This is notified to the stage number conversion circuit 28.

Based on the maximum frame length value 36, the buffer stage number conversion circuit 28 obtains the number k of stages of the buffer 22 necessary for compensating the frequency deviation of the frame transmitted through the network 24, and converts this to the buffer stage number signal 32. To the buffer 22.

Thereafter, when the data of the stage number k notified to the buffer 22 by the buffer stage number conversion circuit 28 is stored in the data receiving unit 21, the buffer 22 notifies the data transmitting unit 23 by the frame extraction signal 31. Data transmission unit 2
3 fetches data from the buffer 22 in response to the frame fetch signal 31, starts regenerating the frame, and transmits the frame to the network 24.

As described above, in the configuration for realizing the second embodiment, the circuit for measuring the frame length itself recognizes the head of the frame and counts the data frame bit length from the timing to recognize the end of the frame. It is a general circuit such as a counter circuit, a comparison circuit that compares whether or not the frame length is the maximum before each measurement of the frame length, a storage register for storing the maximum frame length, and can be easily realized.

As described above, in the second embodiment, each station is provided with a configuration for measuring the data length of a frame passing through its own station within a certain period, and the data is measured based on the measurement result as in the first embodiment. By setting the number of stages of the buffer by determining the timing at which the transmitting unit retrieves data from the buffer, it is possible to prevent a reduction in transmission efficiency due to an unnecessary station delay in the buffer.

In the first and second actual machine methods,
If the maximum frame length of the frame used by the system using the network does not change, there is no problem in setting the number of buffer stages once the optimum value is set when the system is started. However, in the case of a system in which the maximum frame length may vary during the process, the number of buffer stages cannot be fixed at the start of the network system. The third embodiment corresponds to such a case.

In the third embodiment, the measurement of the frame length passing through the own station in the second embodiment is performed not only at the time of starting the system as in the second embodiment, but also in the third embodiment.
The process is performed at regular intervals, and the number k of buffer stages is corrected based on the measurement result each time.

In this way, the optimal number of buffer stages for frequency deviation compensation is always set for the frame length used by the system, so that unnecessary delay at the station does not occur and transmission efficiency is prevented from lowering. I can do it.

Also in the first embodiment, the master station a transmits information for setting the numerical value of the frequency compensation buffer at regular intervals or whenever the maximum length of a frame flowing in the network changes. The same effect can be obtained by issuing the frame 11 and notifying the slave stations b to m.

[0056]

As described above, according to the present invention, the numerical value of the buffer for frequency deviation compensation can be varied according to the performance and state of the system using the network. It is possible to improve the transmission efficiency of the network.

A system using a network is
Even if the maximum frame length used in the process is variable, the optimal number of buffer stages for frequency deviation compensation is always set for the frame length used by the system, resulting in unnecessary delay at the station. Therefore, a decrease in transmission efficiency can be prevented.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic diagram of a ring network system according to a first embodiment.

FIG. 2 is a block diagram of the first embodiment centered on a deviation compensation buffer of each station.

FIG. 3 is a diagram illustrating a method of compensating for a frequency deviation by a deviation compensating buffer.

FIG. 4 is a block diagram of a configuration for realizing a second embodiment.

FIG. 5 is a block diagram showing a data transfer process at each station using a deviation compensation buffer.

FIG. 6 is a diagram illustrating a method of compensating for a frequency deviation by a deviation compensating buffer 102;

[Explanation of symbols]

 1, 21 Data receiving unit 2, 22 Frequency deviation compensating buffer 3, 23 Data transmitting unit 4 Buffer stage number setting unit 10, 24 Ring network 11 Information for setting stage numerical value Frame 25 Frame data length counter circuit 26 Frame Maximum data length storage register 27 Frame length comparison circuit 28 Frame length buffer stage number conversion circuit

Claims (8)

[Claims] 1. A ring network system having one master station and one or more slave stations, wherein the master station transmits a frame including information based on a maximum length of a frame used by a system using the ring network. Generation,
A maximum length notifying unit for transmitting, the slave station includes a buffer unit for buffering data received from the network, a stage number setting unit for setting a stage number of the buffer unit based on information based on the frame, A ring-type network system comprising: 2. The number-of-stages setting unit according to claim 1, wherein the number-of-stages setting unit sets the number of stages of the buffer unit by determining a timing of extracting stored data from the buffer unit for generating a transmission frame. Ring network system. 3. A station device of a ring type network, comprising: frame length measuring means for measuring the length of a frame passing through its own station; buffer means for buffering data received from the network; A stage setting unit for setting the number of stages of the buffer unit based on the longest frame length measured by the frame length measuring unit; 4. The number-of-stages setting unit periodically sets the number of stages of the buffer unit based on the longest frame length measured by the frame-length measurement unit within a certain period. The ring network station device according to claim 3. 5. A method for compensating frequency deviation in a ring network comprising a plurality of stations, wherein a first station transmits a frame for notifying information based on a maximum length of a frame used by a system using the ring network to the network. Wherein each station receiving the frame sets the number of stages of its own frequency deviation compensating buffer based on information from the frame. 6. A method for compensating for a frequency deviation in a ring network comprising a plurality of stations, wherein the station measures a length of a transmission frame passing through the station for a predetermined period, and as a result of the measurement, A frequency deviation compensation method in a ring-type network, wherein the number of stages of a buffer for frequency deviation compensation is set based on the length. 7. The setting of the number of stages of the frequency deviation compensating buffer is performed by determining a timing of extracting stored data from the frequency deviation compensating buffer for generating a transmission frame. A method for compensating for frequency deviation in a ring network as described in the above. 8. The station according to claim 5, wherein the station performs the measurement periodically and sets the number of stages of its own frequency deviation compensation buffer based on the result of the measurement. A method for compensating for frequency deviation in a ring network as described in the above.