KR920005879B1 - Method for transmission of cyclic data - Google Patents

Abstract

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Description

Circular Data Transmission Method

1 is a block diagram showing the configuration of a station of a control dataway according to the first embodiment of the present invention.

2 is a block diagram showing the configuration of a station of a control dataway showing a modification of the first embodiment;

3 is a block diagram showing the configuration of a station of a control dataway according to the second embodiment.

4 is an explanatory diagram of data queued in the transmission buffer memory of the second embodiment.

5 is a block diagram showing a station of a conventional control dataway.

6 is a block diagram of a frame.

7 is a schematic overview of the entire control database.

* Explanation of symbols for main parts of the drawings

1: line 2: line connection

3a: Token Cycle Timer 3b: Token Maintenance Timer

4a: Receive buffer memory 4b: Receive buffer memory

5: DMA transfer control unit 6: circular memory

7: Event transmission control unit 8: External control device

13: Timer for buffer memory transfer

The present invention relates to an update of a shared circular memory in a cyclic data transmission method, in particular, a distributed control transmission method having both cyclic data transmission and event transmission.

5 is a block diagram of one configuration of a station of a control database for realizing the protocol of FDDI (Fiber Distributed Data Interface) introduced in, for example, Telecommunications Vol. 21, No. 5 (issued in May 1987). to be.

In the figure, (1) is a line, (2) is a line connection part, (3) is a media access part connected to the line connection part (2), and the idea access part (3) is a token traversal timer (3a) and a token. It has a holding timer 3b.

(4) is a buffer memory for performing data transmission and reception with the media access unit 3, and this buffer memory 4 has a transmission buffer memory 4a and a reception buffer memory 4b. (5) is a DAM transmission control unit for controlling access to the buffer memory (4), (6) is a cyclic memory for storing synchronization data requiring real time (real time) characteristics, and (7) is not required for real time characteristics. The event transfer control unit 8 for controlling asynchronous data is an external control unit for controlling the cyclic memory 6 and the event transfer control unit 7. As shown, the station 9 is connected to the line connection unit 2, the media access unit 3, the buffer memory 4, the DMA transfer control unit 5, the circular memory 6, and the event transfer control unit 7. It is composed by.

6 shows a configuration diagram of a frame. FIG. 6 (a) is a block diagram showing the token frame 10, where (10-SD) is a start delimiter, (10-FC) is frame control, and (10-DA) is a destination address. (10-SA) is the source address, (10-FC) is the frame check sequence, and (10-ED) is the end delimiter.

6B is a block diagram showing the data frame 11, where (11-SD) is a start delimiter, (11-FC) is frame control, and (11-DA) is a destination addresser. (11-SA) is a source address, (11-INFO) is an information area, (11-FCS) is a frame check sequence, (11-ED) is an end delimiter, and (11-FS) is a frame state.

7 is a schematic diagram of the entire control data way constructed using the station. In FIG. 7, a number of stay lines 9a, 9b, and 9c are connected to the loop-shaped transmission path 12, and each station is provided with a media access unit as shown in FIG. (3), the circulation memory 6 and the event transfer control unit 7 are provided, and the external control devices 8a, 8b, and 8c are connected.

Next, the operation of this configuration example will be described. When the station 9 connected to the loop-shaped transmission path 12 acquires the token frame 10 of the configuration shown in Fig. 6 (a), the station 9 is shown in Fig. 6 (b). The right to transmit the data frame 11 of the configuration is obtained.

At this time, the value of the token circulation timer 3a is copied to the token holding timer 3b, the token circulation timer 3a is set (reset) to a predetermined value, and the clock is started again. Here, the token circulation timer 3a starts revelation from the last token acquisition, and the count of the time from the previous token acquisition to the current token acquisition is executed by subtracting (down counting) from the preset value. Doing. Therefore, the data transfer time of asynchronous data can be known by the value at the time of token acquisition of this token circulation timer 3a, and this value is set in the token holding timer 3b. The preset value set in the token circulation timer is a token circulation target time that becomes a target value of the token circulation time.

At this time, the transmission circulation data of the station 9 is queued in the transmission buffer memory 4a and is in a transmission standby state as synchronous data. However, when the transmission right is obtained, this data is transmitted to the other station 9.

As the timing of transferring the transmission circulation data from the circulation memory 6 to the transmission buffer memory 4a, it is unclear when the next token comes. For example, when a token is acquired or when a token is issued, it is used.

Upon completion of the transmission of the synchronous data, the transmission of the asynchronous data stored in the transmission buffer memory 4a is executed until the token holding timer 3b times out. Here, the timeout means that the timer 3b is counted down to indicate "0".

The token holding timer 3b stops counting when the synchronous data is being transmitted, and executes counting while the hanfun asynchronous data frame is being transmitted. If the token circulation timer 3a has already timed out at the time of token acquisition, asynchronous data transmission is not executed.

According to this method, the time required for transmission of the synchronization data and the synchronization data, that is, the token circulation time, does not exceed twice the value at the reset of the token circulation timer 3a, that is, the token circulation target time.

In this transmission method, if the data amount of synchronization data transmitted by token acquisition, that is, the amount of transmission data of its own station in the cyclic memory 6 is set to be the same each time, the amount of synchronization data is always constant for all stations. The token circulation time does not exceed the token circulation target time preset in the token circulation timer 3a, and a certain responsiveness is assured with respect to the circulating data, so that some improvement is achieved.

The update of the conventional cyclic data has been performed in the above manner. However, since the transmission timing of the cyclic data from the circular memory 6 to the transmission buffer memory 4a is at the time of token acquisition or token issuance, it is transmitted from the circular memory to the transmission buffer memory until it is actually transmitted to the loop-shaped transmission path. There was a problem that the responsiveness of the circulating data was deteriorated by requiring two times (or one) times the token circulation target time.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems, and in the update of the cyclic memory, a circulator that shortens the time required until the data is transmitted from the cyclic memory to the transmission buffer memory and then transmitted to the loop-shaped transmission path. It is to provide a data transmission method.

In order to achieve the above object, the first aspect of the present invention is, for example, after initialization of the loop-shaped transmission system, only synchronous data is transmitted during the first token iteration, and the second token is obtained in the first token acquisition. The token traversal time until acquisition is revealed, and the minimum token traversal time by transmission of synchronous data is measured. After that, if the token acquisition minimum time has elapsed after the token acquisition, the transmission data is transmitted from the cyclic memory to the transmission buffer memory.

In addition, a second aspect of the present invention for achieving the above object is to transmit a dummy frame to a loop-shaped transmission path which no station can receive when obtaining a token, which is queued in the transmission buffer memory during this transmission. The synchronous data frame is updated with data in the cyclic memory.

According to the first aspect of the present invention, the minimum token traversal time due to transmission of synchronization data only is measured in advance, the minimum token traversal time is preset in the token acquisition of the station, and the time is started, and the transmission is performed at the timeout. Generates transfer timing to buffer memory. Therefore, the transmission data of the transmission buffer memory can be updated at the latest time before the next token acquisition.

According to the second aspect of the present invention, upon obtaining the token of the station, the transmission of the dummy frame to the loop-shaped transmission path is started, and the synchronous data frame queued in the transmission buffer memory is updated with the data in the circular memory. Therefore, after completion of the transmission of the dummy frame, the latest cyclic data can be transmitted continuously.

Best Mode for Carrying Out the Invention Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same part as the conventional example mentioned above, and the description is abbreviate | omitted.

[First Embodiment]

1 is a block diagram showing the configuration of a station of the first embodiment. A characteristic feature of this embodiment is that a buffer memory transfer timer 13 is provided which inputs a token acquisition signal from the media access control unit 3 and supplies an output to the DMA transfer control unit 5.

The token frame 10 and the data frame 11 have the same configurations as the conventional example shown in Figs. 6A and 6B, and the token circulation timer 3a and the token holding timer 3b. The same is true of the conventional treatment. And, in this embodiment, when acquiring the token frame 10, each station obtains the right to transmit the data frame 11, but at this time, the value of the token traversal timer 3a is copied to the token holding timer 3b. At the same time, the token circulation timer 3a is reset and retries.

When the transmission right is obtained, the station 9 is queued in the transmission buffer memory 4a and transmits transmission circular data of its own station which is in the transmission standby state as synchronous data.

During the transmission of this synchronization data, the clock of the token holding timer 3b is stopped. After transmission of the synchronous data is completed, the token holding timer 3b starts counting, and if the asynchronous data transmission is queued, the asynchronous data transmission is possible until the token holding timer 3b times out.

Here, the cyclic communication data for each station transmitted in one token acquisition as the synchronization data is fixed, and the sum total of the synchronization data transmitted in the entire loop is always set to be constant per token.

In this way, the preset value of the token circulation timer 3a, which is reset upon token acquisition, that is, the token circulation target time (hereinafter referred to as TTRT) is the time from the token acquisition to the next token acquisition (hereinafter referred to as the token circulation target). Time TRT).

Also, the token circulation target time TTRT is not lower than the total time (hereinafter referred to as the minimum token circulation time Ts) in the loop of the synchronization data transmission time.

Therefore, the next token may not come during the acquisition of the token until the minimum token traversal time Ts in the loop of the synchronization data transmission time.

Therefore, when Ts is measured and transfer from the circular memory 6 to the transmission buffer memory 4 at the time Ts has passed after the token acquisition, the time gap from transmission queuing to token acquisition is reduced.

The measurement of this Ts is performed at the time of initialization of the loop-shaped transmission system. In other words, after initialization of the loop-shaped transmission system, each station only transmits synchronization data in the first token acquisition, measures the time until the next token acquisition, and sets this as Ts.

In the conventional scheme, the time gap between the transmission to the transmission buffer memory 4a and the acquisition of the token was the maximum TTRT even when the data amount of the synchronization data was always the same. According to this embodiment, the TTRT-Ts is improved by Ts. .

Here, the transmission timing to the transmission buffer memory 4a in the measurement of Ts and the acquisition of the token is controlled by the timer 13 for buffer memory transmission. In other words, the buffer memory transfer timer 13 is configured such that Ts described above is preset and counts as a down count upon token acquisition. When counting up, a signal is supplied to the DMA transfer control unit 5, and the synchronization data of its own area in the circular memory 7 is transferred to the transmission buffer memory 4a.

Therefore, the next time the token is acquired, the synchronization data queued to this transmission buffer 4a can be transmitted.

In addition, in the embodiment shown in FIG. 1, a buffer memory transfer timer 13 is used to calculate the transfer timing to the transmission buffer memory 4a by measuring Ts and obtaining tokens. However, if the count value is obtained in the token circulation timer 3a, as shown in FIG. 2, a timer value detection section 14 may be provided instead of the buffer memory transfer timer 13. That is, since the preset value TTRT and the minimum token circulation time Ts in the token circulation timer 3a are known in advance, the progress of Ts after the token acquisition can be known by the value of the token circulation timer 3a. Therefore, the timer value detection unit 14 may maintain the value of TTRT-Ts and transmit when the value is reached.

Second Embodiment

Next, the second embodiment will be described with reference to FIGS. 3 and 4.

The characteristic feature of this embodiment is that a dummy frame is added to the head of the sync frame queued in the transmission buffer memory 4a of FIG. That is, as shown in FIG. 4, a dummy frame is added to the head of the sync frame queued in the transmission buffer memory 4a.

Therefore, when the station 9 acquires the token, it transmits to the line 1 a synchronous frame sequence that is queued in the transmit buffer memory 4a as in the conventional example and is in a transmission standby state as a synchronous frame. The head is a dummy frame. Here, the dummy data frame and the sync data frame are distinguished by FC frame control, and this dummy frame is instructed so that no station performs only relaying without performing reception processing.

The DMA transfer control unit 5, which receives the token acquisition signal during transmission of the dummy frame, updates the cyclic data information of the synchronization data frame with the transmission area data of its own station in the cyclic memory 6 of its own station.

When the length of the dummy frame is longer than the time required for this update, the transmission of the synchronous data frame to the loop-shaped transmission path does not follow the update in the data of its own station transmission area in the cyclic memory 6.

In this way, the synchronous data frame sequence updated by the cyclic data of the transmission area of the own station is transmitted to the line 1 following the dummy frame. That is, although the actual transmission time of the cyclic data of the transmission area of the own station is the maximum token circulation time in the past, in this embodiment, it is the transmission time of the dummy frame. Therefore, the transmission time is shortened by the difference between the token traversal time and the dummy frame transmission time.

In the above embodiment, an example of distinguishing a dummy frame by FC frame control is shown. However, the same operation can be obtained by designating a destination address as an address that does not actually exist and sending it.

As described above, according to this embodiment, the time interval from the transmission to the transmission becomes only the transmission time of the dummy frame, which can greatly improve the real time of the synchronization data.

As described above, according to the present invention, since the transfer of the synchronous data to the transmission buffer memory is performed during the minimum token circulation time or the dummy data transmission, a cyclic data transmission method that can reduce the cost of the device and has a good response can be obtained. Lose.

Claims (2)

Token circulation time from the first token acquisition to the second token acquisition is measured by the token circulation timer, the token holding time that the own station can continue to transmit is measured by the token maintenance timer, and the token is acquired. The token holding time is set according to the token circulation time measured by the token circulation timer, and the token holding time is set in the circular memory which is queued in the transmission buffer memory as data that is required for real time and is transmitted preferentially in token acquisition. The data in the transmission area of the station is sent to all stations as synchronous data, and then the queue is queued in the transmission buffer memory as asynchronous data that does not require real time eventually until the token holding timer times out. The recursion by sending it as asynchronous data In the cyclic data transmission method in which all stations share the contents of the memory, after the initialization of the loop-shaped transmission system, only the synchronization data is transmitted during the first token traversal, and the token from the first token acquisition to the second token acquisition is transmitted. If the minimum time of token acquisition is measured after the acquisition of the token, and the minimum time of token acquisition after the acquisition of the synchronous data has elapsed, the transfer of the transfer data from the circular memory to the transmission buffer memory is performed. Circular data transmission method. If the token traversal time from the first token acquisition to the second token acquisition is measured by the token traversal timer, the token holding time that the own station can continue to transmit is measured by the token maintenance timer, and the token is acquired. Token holding time is set in the token holding timer according to the token circulation time measured by the token circulation timer, and each real time is required, and data in the circulating memory queued in the transmission buffer memory as data transmitted preferentially in token acquisition. It transmits data of its own station's transmission area to all stations as synchronous data, and then queues in the transmission buffer memory as asynchronous data that does not require real time eventually until the token maintenance timer times out. By sending data as asynchronous data In the cyclic data transmission method in which the contents of the exchange memory are shared by all stations, a synchronous frame is transmitted to the loop-shaped transmission path in which a dummy frame, which cannot be received by any station, is queued in the transmission buffer memory during the transmission. Circular data transmission method of updating a data frame with data in circular memory.

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