JP3043885B2 - Data synchronous transmission system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data synchronous transmission system having a synchronization function at the start of data transmission for each transmission cycle.

[0002]

2. Description of the Related Art Hitherto, in a high-speed transmission system such as FDDI adopting a token passing system, it is impossible to perform so-called fixed-cycle transmission. This is because, in order to perform periodic transmission, the transmission start time of each station must be adjusted to a certain timing. However, in a high-speed transmission system such as FDDI, the accumulated error in the timing of the transmission start time after a certain time elapses. This is because it becomes too large.

[0003] In order to overcome such disadvantages,
The applicant has previously proposed Japanese Patent Application No. Hei 1-209783. This technical content is that any one of a plurality of stations is determined as a synchronization control station, and this synchronization control station attempts to transmit a dummy frame before starting transmission of a data frame. Then, the length of the dummy frame is expanded and contracted in accordance with the transmission start time of the data frame, so that the transmission start time of the data frame can be made to coincide with the reference timing, thereby enabling the periodic transmission.

[0004]

Although the data synchronous transmission system described above makes it possible to carry out periodic transmission, the data transmission start time of the synchronous control station is different from the reference timing due to various factors during the data transmission. In some cases, a mismatch occurs.

[0005] In such a case, the synchronous control station detects a deviation with respect to the reference timing, that is, a deviation between the input timing of the reference timing signal supplied from the outside and the data frame transmission start timing. By re-calculating the length of the dummy frame, the deviation with respect to the reference timing is corrected.

[0006] However, even if the length of the dummy frame is correct, if the reference timing signal is incorrect, a shift in reference timing occurs again. Since the reference timing signal is supplied from outside the system, it has been difficult to correct the deviation of the reference timing by controlling the system.

[0007] The present invention has been made in view of the above circumstances, and even if the reference timing signal becomes abnormal, it is possible to continue the periodic transmission and thereby improve the reliability of the system. It aims to provide a synchronous transmission system.

[0008]

According to the present invention, as a means for solving the above problems, when performing data transmission by a token passing method between a plurality of stations, one of the stations is set as a synchronization control station, In a data synchronous transmission system in which the control station generates a dummy frame and adjusts the dummy frame length so that the synchronous control station data transmission start time coincides with a reference timing signal supplied from the outside, The synchronization control station includes: a reference timing signal monitoring circuit that monitors whether a cycle of the reference timing signal is normal; and a dummy frame length refined when the cycle of the reference timing signal is normal. A dummy frame length monitoring circuit for monitoring whether or not the Enter the monitoring result of the long monitoring circuit,
A monitoring operation command circuit that outputs a monitoring operation continuation signal when the dummy frame length is abnormal, and outputs a synchronous control station switching signal when the period of the reference timing signal is abnormal, And any other station having the same function as the synchronous control station, and its reference timing signal supply source as a different supply source from the synchronous control station. When the circuit outputs the synchronous control station switching signal, the spare synchronous control station functions instead of the synchronous control station.

[0009]

In the above configuration, assuming that the synchronous control station has received a token, the synchronous control circuit calculates a period from the time when the token is received to the time when the next reference timing signal is input, and corresponds to this period. Transmit a dummy frame of length. After the transmission of the dummy frame is completed, the data frame is transmitted, and after the transmission is completed, the token is transferred to another station determined as the next transmission order. As described above, when the token sequentially circulates the other stations and the transmission of the data frame in each station ends, the synchronization control station receives the token again and performs the same operation as described above.

At this time, in the synchronous control station, the reference timing signal monitoring circuit and the dummy frame length monitoring circuit perform monitoring operations, respectively. If the length of the dummy frame is abnormal, the monitoring operation command circuit continues the monitoring operation. This is because an error in the dummy frame length is merely a software error, and it is considered that if the transmission operation is continued as it is, there is a high possibility that the error state will be gradually eliminated.

However, if the period of the reference timing signal is abnormal, the monitoring operation command circuit outputs a signal indicating that the synchronous control station should be changed. This is a malfunction of the reference timing signal supply source outside the synchronous control station, that is, an error on the hardware, with respect to the abnormality of the cycle of the reference timing signal.
This is because even if the dummy frame length is appropriate, it is considered that a deviation with respect to the reference timing will occur eventually.

When the synchronous control station receives the synchronous control station switching signal, the synchronous control station assumes the role of the synchronous control station, for example, by generating a dummy frame. . In this case, since the reference timing signal supply source supplied to the preliminary synchronization control station is different from that used for the synchronization control station, the period of the reference timing signal also returns to the normal state. Will be.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 2 is a block diagram illustrating a schematic configuration of the data synchronous transmission system according to the embodiment. In this system, the token ring method of the token passing method is adopted, and the stations S ₁ , S ₂ , S _{3 ,.}
The tokens (transmission rights) are circulated in the order of.

The station S ₁ is defined as a synchronous control station, and a reference timing signal R ₁ is transmitted from a reference timing signal generator 1 as a reference timing signal supply source via a public line or the like. It has become. The station S ₃ is defined as a standby synchronization control station. When the synchronization control station switching signal is transmitted from the station S ₁ , the station S ₃ is supplied from the reference timing signal generator 2 separate from the reference timing signal generator 1. based on the reference timing signal R ₂ which is, so that it is possible to perform the operation as the synchronous control station on behalf of the station S _1.

[0015] previously described based here, the outline of each transmission timing of the station S ₁ to S _n in the time chart of FIG.
The reference timing signal R ₁ is assumed to be generated for every predetermined circumferential groups T. Now, the time when the station S ₁ at t ₀ is to have received the token, the station S ₁ is dummy data D _m of length l ₁ corresponding to the period until the input time t ₁ of the reference timing signal R ₁ from time t ₀ sends, subsequently transmits a data frame D ₁ and tokens.

Next, upon receiving this token, the station S ₂ transmits a data frame D ₂ and further transmits a token. Hereinafter, the token is similarly circulated, and each station transmits a data frame while holding the token.

At time t ₂ , the station S ₁ becomes the station S _m
, The station S ₁ transmits dummy data D _m having a length l ₂ corresponding to a period from the time t ₂ to the input time t ₃ of the next reference timing signal R ₁ , and then the data frame D 1 Send ₁ and the token. in this way,
Since the station S ₁ as a synchronization control station appropriately changes the length of the dummy frame for each transmission cycle,
Transmission start time point of the data frame D ₁ is always coincident with the reference timing signal R _1. As for the other stations S ₂ to S _n, each transmission time is constant timing.

[0018] FIG. 1 is a block diagram showing the configuration of the station S ₁ in FIG. As shown in this figure, the station S ₁ transmission control circuit 3, the synchronization control circuit 4, a microprocessor unit (MPU) 5 in the formed monitoring operation instruction circuit 6, a reference timing signal monitoring circuit 7, a dummy frame length monitor The circuit 8 is provided.

The transmission control circuit 3 has a built-in token passing transmission protocol and performs transmission and reception with other stations. The transmission control circuit 3 detects a token from the data sent from the station S _n, and outputs a detection signal to the synchronization control circuit 4.

The synchronization control circuit 4 includes a reference timing signal R ₁ from the reference timing signal generator 1 calculates the dummy frame length based on the token detection signal from the transmission control circuit 3, transmission control of the operation result The signal is output to the circuit 3. Transmission control circuit 3 generates a dummy frame based on the calculation result, and sends this to the station S _2.

This dummy frame, as described,
This frame does not need to be taken in by any station on the transmission path, and is used for time adjustment on the transmission path. Therefore, for example, a dummy frame can be created by setting the destination station address in the frame to a station address value that does not exist on the transmission path.

The transmission control circuit 3 and the synchronization control circuit 4
And the MPU 5 are connected by a data bus 9,
An instruction of an operation mode, a state display, data exchange, and the like are performed between each other.

On the other hand, the reference timing signal monitoring circuit 7
And it receives the reference timing signal R ₁ from the reference timing signal generator 1, so as to determine whether the period of this signal is within a predetermined value within a certain range (e.g., 5%) Has become. Then, the determination result as a signal for displaying the state of the reference timing signal R _1, are sent to the monitoring operation command circuit 6 and the synchronous control circuit 4.

In the synchronous control circuit 4, if the status indication outputted from the reference timing signal monitoring circuit 7 indicates that it is within a certain range, that is, it is normal, the reference timing signal from the reference timing signal generator 1 is output. The above-described calculation of the dummy data frame length is performed using R ₁ as it is. However, if the status display output from the reference timing signal monitoring circuit 7 indicates that the status display is out of the predetermined range, that is, it is abnormal, the synchronization control circuit 4 stores the previous reference timing signal held therein. Is used to calculate the dummy frame length. At the same time, the monitoring operation command circuit 6 is notified via the data bus 9 of the reference timing error state. This reference timing error state is maintained until the error state is cleared by a command from the monitoring operation command circuit 6.

The dummy frame length monitoring circuit 8 receives the calculation result from the synchronization control circuit 4 and checks whether the dummy frame length falls within a certain range defined by the upper limit value and the lower limit value. It is determined.
The determination is sent to the monitoring operation circuit 6 and the synchronization control circuit 4 as a signal indicating the state of the dummy frame length.

In the synchronization control circuit 4, if the status display output from the dummy frame length monitoring circuit 8 indicates that the status display is within a certain range, that is, normal, the calculation result is output to the transmission control circuit 4 as it is. I do. However, when the status display indicates that the state is out of the predetermined range, that is, that the state is abnormal, the synchronization control circuit 4 performs the following output.

That is, when the status display from the dummy frame length monitor circuit 8 indicates that the upper limit value is exceeded, the synchronization control circuit 4 outputs the upper limit value to the transmission control circuit 3 as a dummy frame length. If the lower limit is indicated, the lower limit is output to the transmission control circuit 3 as the Bummy frame length. In other words, even if the length of the dummy frame is greatly changed, the dummy frame length is not greatly changed at once, and the dummy frame length is corrected stepwise with a change width within an allowable range. I have. And the synchronization control circuit 4
At the same time, the monitoring operation command circuit 6 is informed of the dummy frame length error state. This dummy frame length error state is maintained until the error state is cleared by a command from the monitoring operation command circuit 6.

Next, the operation of the monitoring operation command circuit 6 will be described with reference to the flowchart of FIG. First, the monitoring operation command circuit 6, the state indication signal from the reference timing signal circuit 7, the period of the reference timing signal R ₁ is equal to or normal (step 1). If it is normal, the synchronization is permitted to the synchronization control circuit 4 in order to add a dummy frame to the head of the queue of transmission frames of the transmission control circuit 3 which is already operating (step 2).

As a result, the synchronization control circuit calculates the dummy frame length. The monitoring operation command circuit 6 determines whether or not the dummy frame length is normal based on the status display signal of the dummy frame length monitoring circuit 8. (Step 3). If normal, the reference timing error state and the dummy frame length error state held in the synchronization control circuit 4 are cleared in advance (step 4), and the synchronization control circuit 4 is allowed to monitor an automatic error (step 4). Step 5).

Thereafter, the synchronization control circuit 4 performs operations such as the calculation of the dummy frame length as described above, and the monitoring operation command circuit 6 waits for the occurrence of the reference timing error state or the dummy frame length error state (step S1). 6). In this case, the error state is detected by the synchronization control circuit 4.
Monitors the interrupt signal via the data bus 9
Or the monitoring operation command circuit 6 may periodically read the status register of the synchronization control circuit 4.

When any of the error states is detected, the monitoring operation command circuit 6 prohibits the synchronous control circuit 4 from performing automatic error monitoring (step 7). Then, the monitoring operation command circuit 6 reads the status register of the synchronization control circuit 4 and determines whether this error is a dummy frame length error or a reference timing error (step 8). In the case of a dummy frame length error, the flow returns to step 4 to clear the error state, and the automatic error monitoring is started again (step 5).
This is because the fact that the dummy frame length is abnormal even though the reference timing is normal means that there is a high possibility that a dummy frame length error has occurred due to a software error such as an operation error. Alternatively, it is considered that the dummy frame length can be returned to a normal value by performing the correction stepwise with the lower limit value as the dummy frame length.

On the other hand, if the error is a reference timing error, the monitoring operation command circuit 6 counts the number of occurrences of this error. Then, a predetermined number of times (m
If an error occurs, the monitoring operation command circuit determines that there is no possibility that the reference timing error state returns to normal, and instructs the synchronization control circuit 4 to stop the synchronization operation (steps 9 and 10). It should be noted that the synchronization control circuit 4 operates until the number of occurrences of the reference timing error reaches m.
The dummy frame length is calculated using the cycle of the reference timing signal before the occurrence of the error, and synchronization is attempted.

After instructing the synchronization control circuit 4 to stop such a synchronization operation, the monitoring operation command circuit 6 outputs a synchronization control station switching signal to the transmission control circuit 3 (step 1).
1). Transmission control circuit 3 sends to the station S ₂ the frame added with the sync station switching signal as the station S ₃ addressed a preliminary synchronization control station. This frame is input to the station S ₃ through the station S _2. Thus, the station S _3, using the reference timing signal R ₂ from the reference timing signal 2, a synchronization control station S ₁ is was performed until it is performed on behalf of the station S _1. In this case, the reference timing signal generator 2
Since the reference timing signal generator 1 is distinct independent, never cycle of the reference timing signal R ₂ is abnormal.

[0034]

As described above, according to the present invention, a spare synchronization control station having a reference timing signal supply source separate from that of the synchronization control station is provided, and the reference timing signal supplied to the synchronization control station is provided. When an error occurs, the synchronization operation is switched from the synchronous control station to the standby synchronous control station, so that constant-cycle transmission can be continued regardless of the occurrence of an error in the reference timing signal, improving system reliability. It is possible to do.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a synchronization control station according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a schematic configuration of a system according to an embodiment of the present invention.

FIG. 3 is a flowchart for explaining the operation of FIG. 1;

FIG. 4 is a time chart for explaining the operation of FIG. 2;

[Explanation of symbols]

S ₁ Synchronous control station S ₃ Preliminary synchronous control station R ₁ , R ₂ Reference timing signal 1, 2 Reference timing signal generator 6 Monitoring operation command circuit 7 Reference timing signal monitoring circuit 8 Dummy frame length monitoring circuit

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04L 7/00 G06F 13/368 H04L 12/42

Claims (1)

(57) [Claims] When performing data transmission by a token passing method between a plurality of stations, one of the stations is set as a synchronization control station, the synchronization control station generates a dummy frame, and adjusts the dummy frame length. In the data synchronous transmission system, the synchronous control station is configured to make the data frame transmission start time coincide with a reference timing signal supplied from the outside, wherein the synchronous control station determines whether a cycle of the reference timing signal is normal. A reference timing signal monitoring circuit that monitors whether the dummy frame length generated when the cycle of the reference timing signal is normal is normal; and a reference timing. The monitoring result of the signal monitoring circuit and the dummy frame length monitoring circuit is input, and the dummy frame length is abnormal. And a monitoring operation command circuit that outputs a monitoring operation continuation signal, and outputs a synchronous control station switching signal when the period of the reference timing signal is abnormal. A similar function is provided to any other station, and its reference timing signal source is different from this synchronous control station.
This is a standby synchronous control station, and when the monitoring operation command circuit outputs the synchronous control station switching signal, the standby synchronous control station is made to function in place of the synchronous control station. Data synchronous transmission system.