JP2731430B2 - Data communication method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data communication method, and more particularly to a data communication method in which transmission between terminals is fixedly assigned to a plurality of time-division multiplexed channels.

[Prior Art] A conventional loop data transmission method in which transmission between terminals is fixedly assigned to a plurality of time-division multiplexed channels will be described with reference to FIGS. 2 to 7. FIG.

A plurality of stations S1 to S6 are interconnected to the transmission line 1,
Are configured in a loop. Each station has various terminals T1 ~
T12 is connected, and voice, data, images, and the like are transmitted between the terminals. FIG. 2 shows a system configuration in which the number of stations is 6, and two terminals are connected to each station, but similar effects can be obtained regardless of the number of stations and the number of connected terminals.

Time-division multiplex transmission channel C ₁ -C _l of fixed length constitute 1 Ke frame, the transmission line 1 the frame is repeated
Orbit above. A channel is assigned to each transmission between terminals.

As shown in FIG. 4, the assignment of channels will be described using four transmissions as an example. Between terminals connected to the transmission 1 in the station S1 and S4 and 1: 1 a case of performing two-way transmission, using channel C _1. The station S1 is sending data to detect and channel C _1, and transmits. Station S4, detects the channel C _1, after receiving the data from station S1, and sends the write data to the station S4 is transmitted to the channel C _1. As a result, 1: 1 bidirectional transmission can be performed using one channel. In addition, transmission between two terminals in the same station is based on 1: 1 one-way transmission of transmission 2 described later.
Perform using pairs.

Next, in transmission 2, the terminal connected to station S2
1: 1 one-way transmission to the terminal connected to. The channel C ₂ used in the transmission, station S2 writes the transmitted data to the channel C _2, the station S5 is to receive the data.

In transmission 3, the terminals connected to station S4 are the master station, and stations S3 and S6.
The terminal connected to becomes a slave station and performs 1: n polling selection transmission. Channel C ₃ from master station S4 to slave stations S3 and S6
Used, transmitted using the channel C ₄ from the slave station S3 or S6 to the master station S4.

Transmission 4 is from terminals connected to station S6 to stations S1 and S3.
Performs 1: n broadcast transmission to the terminal connected to.
Here transmitted by S6 station using channel C ₅ is the station S1 and station S3 is receiving data from the channel C _5.

FIG. 5 shows a use state of each channel when a frame including five channels is used for transmission. In the figure, the data transmitting station is indicated by a square mark, and the receiving station is indicated by a solid circle.

As can be seen from the above, the usage of each channel can be classified into two types, one channel used for two-way transmission and one channel used for one-way transmission. In the latter case, 1: 1 and 1: It can be classified into n.

By the way, in time-division transmission with fixed channel connection, the transmitting station periodically updates and transmits data every time an assigned channel is detected. On the other hand, each time the receiving station detects the assigned channel, it determines that the data is from the transmitting station and receives it.

Therefore, when an error such as a failure of the transmitting station or the transmitting terminal or a disconnection from the transmission path 1 occurs, transmission data immediately before the transmission station becomes abnormal circulates on the transmission path 1. However, the receiving station must confirm that the received data has been updated at the transmitting station,
Alternatively, there is a disadvantage that it cannot be determined whether or not it is old.

Also, a slave station responds to the request from the master station in a 1: n polling selection. Therefore, data may be transmitted from the slave station to the master station at a certain time, but none of the slave stations may transmit data at another time. In the latter case, there is a disadvantage that the last data transmitted by a certain slave station circulates on the transmission path, and the master station receives the data already received many times until the slave station transmits new data.

As one method to solve these drawbacks, NCC
Sutrol, A Local Communications Network-Based on the Interconnected Token Access Rings, IBM
Journal of Research and Development, vol5 No.5 481-496 (NCStrole, A Local Commun
ications Network Based on the Interconnected Token
−Access Rings, IBM Journal of Research and Develop
ment vol.27 No.5 P481-496), a monitoring bit W is added to the information section I as shown in FIG.
A predetermined station on the transmission line becomes a monitoring station,
The transmitting station transmits the monitoring bit W as "0", and the monitoring station changes the monitoring bit W from "0" to "1" and transmits it. When the monitoring station receives the data in which the monitoring bit W is "1", the monitoring station determines that the data is abnormal data and discards the data from the transmission line 1. This method can prevent the abnormal data from going around the transmission line 1 more than once. However, in this method, the same data may be received twice depending on the connection order of the transmitting station, the receiving station, and the monitoring station to the transmission path. This will be described with reference to FIG.

Now, the transmitting station is S1, the receiving station is S2 and S4, the monitoring station is S3,
It is assumed that stations S1, S2, S3, S4, and S1 are connected to the transmission line 1 in this order. When the transmitting station S1 transmits data, the monitoring bit W
Is transmitted as “0”. The receiving station S2 receives the data, and the monitoring station S3 changes the monitoring bit W from "0" to "1" and transmits the same. The receiving station S4 receives the data. After the transmitting station S1 transmits data, if an abnormal state occurs, the data is not changed and the receiving station S2 receives the data again. The monitoring station S3 has the monitoring bit W
Is "1", this data is determined to be the second round, and this data is deleted. Therefore, the receiving station S4 does not receive the same data. That is, the receiving station S2 receives the same data twice, but the receiving station S4 receives the same data only once.

As described above, there is a disadvantage that the same data is received twice depending on the connection order of the transmitting station, the receiving station, and the monitoring station.

[Problems to be solved by the invention]

The above conventional technique has a problem that the same data circulates and receives data unless the transmitting station is abnormal or new data is transmitted.

An object of the present invention is to prevent a receiving station from receiving the same data that goes around.

Another object of the present invention is to provide bidirectional transmission between two stations using the same channel, and to prevent another station from receiving abnormal data even if one station becomes abnormal.

Another object of the present invention is to provide one-way transmission between two stations using one channel, and to prevent the receiving station from receiving data when the transmitting station is abnormal.

Another object of the present invention is to automatically select a receiving station that determines not to receive abnormal data due to a transmitting station error in 1: n broadcast transmission using one channel.

Another object of the present invention is to prevent the master station from detecting old data and not receiving it when the slave station does not transmit data in the 1: n polling selection transmission.

[Means for Solving the Problems] The above objects are achieved by terminals connected to each station circling a frame composed of a plurality of channels which are time-division multiplexed on a transmission line connecting a plurality of stations in a ring. In a data communication method for performing data transmission using channels fixedly allocated to inter-station transmissions, each of the channels is composed of a channel header and an information section, and the channel header includes a station identification code and a monitoring bit. , An information valid bit and a parity bit, and the receiving station receives the information portion of the channel when the station identification code of the received channel is the station identification code of the transmitting station, and sets the monitoring bit to be set by the transmitting station. In the state, the receiving station receives the information section of the channel and resets the monitoring bit, the information valid bit is set in the transmitting station, and the receiving station identifies the station. When it is determined from the code or the monitoring bit that the data is abnormal data and the information of the channel is not received, the information valid bit is reset at the receiving station, and the receiving station determines the parity of the channel head of the corresponding channel based on the parity bit. This is achieved by performing a check and changing the station identification code, monitor bit, and information valid bit only when the status is normal.

[Action]

A station identification code, a monitor bit, an information valid bit, and a parity bit are provided in a channel header, and the station identification code is set in advance between two stations or between a transmitting station and a receiving station. The monitoring bit is set in the transmitting station and reset in the receiving station. The information valid bit is transmitted in a set state by the transmitting station, and the receiving station determines whether the channel header is normal or abnormal. If the data is abnormal, the information valid bit is changed to the reset state.

Therefore, in two-way transmission between two stations using the same channel, if the received station identification code matches the station identification code of the partner station, it is determined to be normal, and if it matches the station identification code of its own station, it is determined to be abnormal, Reset the information valid bit.
In one-way transmission, the receiving station changes the monitoring bit to a reset state and transmits it to the next station. Therefore, the monitoring bit indicates that the data in the reset state has already been received, and when receiving the data in which the monitoring bit is in the reset state, the information valid bit is reset.

In 1: n transmission in which there are a plurality of receiving stations, the immediately downstream receiving station determines the content of the channel header, changes the channel header according to the result, and transmits it to the next station. Other receiving stations determine whether or not to receive according to the set / reset state of the information valid bit of the received channel header, but do not change the channel header. The immediately downstream receiving station is determined for each channel from the contents of the channel header.

Two-way transmission or one-way transmission, the two station identification codes in two-way transmission, and the distinction between the transmitting station and the receiving station in one-way transmission are stored in the mode register for each channel. Then, the corresponding mode register is read.

Therefore, even if the transmitting station becomes abnormal and the same data circulates on the transmission path, the receiving station does not receive the same data a plurality of times.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to FIG. 8 and FIG.

Channel C ₁ -C _l constituting a frame to be transmitted on the transmission path 1 as is shown in each FIG. 8, the channel header
CH and information section I. Further, the channel header CH is
It includes a parity bit P, a station identification code D, a monitor bit M, and an information valid bit V. In this embodiment, the station identification code D
Is described with one bit, but there is no limitation on the bit length in the present invention. In the channel header CH, parity bits P,
The case where the station identification code D, the monitoring bit M, and the information valid bit V are arranged in this order will be described, but there is no restriction on the arrangement order in the present invention.

The check range of the parity bit P will be described with the station identification code D, the monitor bit M, and the information valid bit V, but may be the channel header CH or the channel CH and the information section I. The parity bit P may be odd parity or even parity.

FIG. 9 shows the setting conditions of each bit in the channel header CH shown in FIG. 8 and the immediately downstream receiving station flag DNR indicating the immediately downstream receiving station which first receives data from the transmitting station among the plurality of receiving stations. It is explained based on.

The station identification code D is an identification code of the transmitting station itself specified by a mode register for each channel described later, and is set in a channel header and transmitted. Required for bidirectional transmission between two stations using the same channel and the first station is "1"
Then, the other stations are set to “0”. The receiving station does not change the station identification code D.

The monitoring bit M is transmitted as "1" at the time of data transmission, changed to "0" at the receiving station, and transmitted to the next station. This allows
It is possible to detect that the data is not updated when the transmitting station is abnormal in one-way transmission.

The information valid bit V is transmitted by setting “1” indicating that data is valid at the time of data transmission. The receiving station has the following two modes depending on the transmission mode. In the 1: 1 two-way transmission mode on the same channel, if the received station identification code D is the station identification code of the partner station, the information valid bit V is "1" without any change since the partner station has correctly updated it. However, if the received station identification code D is the station identification code of the own station, the data is not updated at the partner station, and the data transmitted by the own station has returned through the transmission line 1 and is correct. Not data. Therefore, the information valid bit V
To “0”.

When the information valid bit V in the one-way transmission mode is the immediately downstream receiving station and the monitoring bit M is "0", the same data is received a plurality of times, and is changed to "0" and transmitted to the next station. You. On the other hand, the information valid bit V is not changed except at the immediately downstream receiving station and when the monitoring bit M is “0”. That is, data is transmitted, the first round is valid, the second round is determined to be abnormal, and is changed to invalid, and the third and subsequent rounds are abnormal but already “0”
It does not need to be changed because it has been changed to

The immediately downstream receiving station flag DNR is used in the one-way transmission mode. If there is only one receiving station, this receiving station is always eligible to be the immediate downstream receiving station. On the other hand, in the transmission of a plurality of receiving stations, the first receiving station from the transmitting station is the direct downstream receiving station, but if the direct downstream receiving station becomes abnormal, the direct downstream receiving station is selected from other receiving stations. The station to be the station is selected, and the new immediately downstream receiving station determines whether the received data is normal or abnormal. Accordingly, the direct downstream receiving station treats the number of receiving stations as one or a plurality of stations in the case of one-way transmission in the same manner.

The immediately downstream receiving station flag DNR is set each time the monitoring bit M transmitted by the transmitting station is received and is "1". Since the monitoring bit M is changed to "0" at the receiving station, another receiving station cannot be a direct downstream receiving station.

The transmitted data is received by all the receiving stations in the first round. If an error occurs after the transmitting station has transmitted the data, the same data makes two rounds, but is not received because the information valid bit V is reset at the immediately downstream receiving station.

The immediately downstream receiving station flag DNR is reset by the channel header when the monitoring bit M is reset and the information valid bit V is reset at the immediately downstream receiving station. In other words, when the same data has made three rounds, the immediately downstream receiving station flag DNR is reset.

The transmission line 1 has a value of 1
One or a plurality of frames continuously circulate. When a plurality of frames circulate, data of the same channel of each frame on the transmission path is transmitted. When the transmitting station becomes abnormal, the information valid bit V of the corresponding channel of all frames on the transmission path is set to "0". For this reason, the immediately downstream receiving station flag is set to the set state during a period in which the abnormal data makes three rounds.

The parity bit P is obtained from the station identification code D, the monitoring bit M, and the information valid bit V at the transmitting station in the case of an odd parity by the following equation.

The receiving station performs a parity check from each bit of the received channel header CH, and if normal, determines / changes each bit. Do not change in the case of a parity error.
If paraffin wax is normal, the new parity bits, station identification code D, using the effective bit V _C monitored bit M _C and information that has changed And transmitted to the next station.

Each bit in the channel header CH and the truth value of the immediately downstream receiving station flag shown in FIG. 8 are shown in FIG. 9, and a circuit example for realizing this will be described with reference to FIGS. 1 and 10. .

The stations S1 to S6 are connected to the loop transmission line 1 in the order shown in FIG. A terminal is connected to each station, and a terminal is connected to station S1.
Although T1 and T2 are connected, there is no restriction on the number of connected terminals.

The stations S1 to S6 have the same configuration, and the description will be made using the station S1 in FIG.

The serial data received from the transmission path 1 is subjected to waveform shaping,
The data is input to a serial / parallel conversion circuit 3 that performs parallel data conversion and extracts a frame synchronization signal and a channel synchronization signal via a receiver 2 that extracts a timing clock.

From the serial-parallel conversion circuit 3, a reception header CH _R, which is a channel header received for each channel, is converted into a header determination change circuit 4
To, receiving information part I _R received is input to the reception buffer 5 and the selector 8 stores the received data. Based on the frame synchronization signal and the channel synchronization signal extracted by the serial / parallel conversion circuit 3, the timing control circuit 11 stores the mode register 12 storing the mode for each channel and the register 39 of the immediately downstream reception station flag. It outputs a mode command 22 for selecting each channel, a buffer command 21 for instructing storage and reading in the reception buffer, and a buffer command 23 for instructing storage and reading of transmission data from the terminal.

In the mode register 12, the transmission mode of each channel and the station identification code of the own station are stored in advance, and the mode register of the next channel is accessed for each mode command 22, and the mode 24 and the own station identification code 25 are read. Output to the header determination change circuit 4. The own station identification code 25 is also output to the header generation circuit 13.

The header determination change circuit 4 executes the processing shown in FIG. 9, and an embodiment will be described with reference to FIG.

The received reception header CH _R is output from the serial / parallel conversion circuit 3, and the parity bit P is input to the parity check circuit 31 and the fourth selector 44. The station identification code D parity check circuit 31 is inputted to the coincidence judgment circuit 33 and the parity generation circuit 43, a further station identification code of the new header CH _C which is the output of the header determining changing circuit 4.

The monitoring bit M is transmitted to the parity check circuit 31, the first selector 34, the inverter 36, the AND circuit 36, and other AND circuits.
Entered in 40. The information valid bit V is input to the parity check circuit 31, the inverter 35, the second selector 41, and the third selector 42.

But the parity check circuit 31 to perform the determination whether the channel received header is correct, performs the determination changes if correct, in case of parity error, header CH _R a header determining changing circuit as received The output is a new header CH _C. The header normal 45, which is the check result of the parity check circuit 31, is “1” level when correct.
In the case of a parity error, the signal becomes “0” level, becomes an input of a selection instruction signal of the first selector 34, the third selector 32, and the fourth selector 44, and is further input to AND circuits 37 and 38.

Station identification code D of the match determining circuit 33 receives the header CH _R
And a signal obtained by inverting the own station identification code 25 from the mode register 12 by the inverter 32 is determined. If they match, they output "1", and if they do not match, they output "0" and are input to the second selector 41. If the mode 24 read from the mode register 12 is the same-channel two-way transmission, it becomes the output of the second selector 41. header normal 45 is new information valid bit V _C which is the output of the third selector 42 when there is "1" level. That is, when the received data is new information valid bit V _C as long as from the partner station is "1", the data of the local transmission becomes other station abnormality came back after searching the transmission path 1 new information valid bit V _C is "0".

The first selector 34 is “0” when the normal header 45 is “1”.
The outputs when That monitoring bit M received when the parity error "0" to the new monitoring bits M _C. Therefore, when data is received, the monitoring bit M is set to "0".

The register 39 for storing the immediately downstream receiving station flag DNR corresponds to the number of channels, one of which is selected by the mode command 22 operates, the header normal 45 indicates "1", and the mode 24 indicates one-way transmission and indicates "1". And the monitoring bit M is “1”, the AND circuit 37
Becomes "1" level, and one register selected by the mode command 22 is set to "1". On the other hand, the output of one register 39 selected by the mode command 22 is "1" via the fifth selector 46, that is, the immediately downstream receiving station flag DNR is set, and the header normal 45 is "1". When 24 is "1" and the monitoring bit M and the information valid bit V are both "0", the condition of the AND circuit 38 is satisfied and the register 39
Is reset, and it is no longer the immediate downstream receiving station.

The output of the register 39 becomes another input of the AND circuit 40, another selection signal input of the second selector 41, and an input of the AND circuit 38. If the mode 24 is "1", that is, one-way transmission and the immediately downstream receiving station flag DNR is "1", the received monitoring bit M
Is normal via the AND circuit 40 and the second selector 41
If 45 is "1", it becomes the output of the third selector 42 and becomes the new information valid bit Vc. Therefore, if the monitoring M received by the immediately downstream receiving station is "1", the data is normal, and if the monitoring bit M is "0", the data is determined to be abnormal data.

When the mode 24 is "1", that is, in the case of one-way transmission and the immediately downstream receiving station flag DNR is "0", the received information valid bit V becomes the output of the second selector 41 as it is, and the header normality 45 becomes "1". If it is 1 ", the output of the third selector 42 is obtained. Therefore, a receiving station that is not a direct downstream receiving station in one-way transmission does not change the information valid bit indicating normal / abnormal data.

Newly generated new monitoring bit M _C , new information valid bit
V _C and received station identification code D is input to the parity generation circuit 43, parity bits are generated. The output of the parity generation circuit 43 is input to the fourth selector 44 and the header is normal.
45 is selected by the fourth selector 44 if "1", the new parity bit P _C. On the other hand, when the header normality 45 is “0”, the received parity P is selected by the fourth selector 44,
Is output.

Register 39 in FIG. 10 is required for the number of channels,
This may be realized by a random access memory.

New header which is the output of the header determination change circuit 4 in FIG.
CH _C, the new parity bit P _C shown in FIG. 10, station identification code D, the new monitoring consists bit M _C and new information valid bit V _C, the received information is the output of the serial-parallel conversion circuit 3 to the reception buffer 5 stored with part I _R. The contents of the reception buffer 5 are read out when instructed by the buffer command 21, and are read by the bus 27.
Is input to the terminal T1 or the terminal T2 via the.

Next, the transmitting side will be described with reference to FIG. Terminal
Information transmitted from T1 or terminal T2 starts bus 27,
The data is stored in the transmission buffer 6. Among stored data, data corresponding to the channel is output as a new information unit I _N by the buffer command 23 is input to the selector 8.
The other input of the selector 8 receives information part I _R is connected, the output of the selector 8 is selected by the other output is selected command 26 of the transmission buffer 6.

Further, the parity bit P, the station identification code D, the monitoring bit M, and the information valid bit V of the channel header CH are generated by the header generation circuit 13 via the station identification code 25 output from the mode register 12, and the generated header is generated. CH _G is connected to one input of the selector 7. Here, the monitoring bit M and the information valid bit V are “1”. The other input of the selector 7 is a new header generated by the header determination change circuit 4.
CH _C , one of which is selected by the selection command 26.

The selectors 7 and 8 output the generated header CH _G by the selection command 26 on the channel to which the connected terminals T 1 and T 2 transmit data.
And select the new information unit I _N, the new header CH _C changing the received data in the channel which does not transmit the data of the terminal T1, T2
Selecting a received information portion I _R and.

Transmission header CH _T and transmitting information section I _T, which is the output of the selector 7 and 8 are data to be transmitted, the parallel-serial conversion circuit 9
Is transmitted to the transmission line 1 from the station S1 via the driver 10 and transmitted to the next station S2.

An example of the state of each bit in the channel header CH will be described with reference to FIGS. 11 and 12. FIG. 11 shows an example in which the stations S1 and S4, which are the transmission 1 in FIG. 4, perform bidirectional transmission using one channel. In FIG. 12, the station S6, which is the transmission 4, is a transmitting station.
An example of one-way transmission of 1: n in which the stations S1 and S3 are receiving stations will be described. In both figures, a 4-bit 1, 0 numeral string indicates the values of the odd parity bit P, the station identification code D, the monitor bit M, and the information valid bit V in order. In the drawing, a circle indicates that data is received at the station, and a cross indicates that data is not received. Further, for simplicity of description, here, it is assumed that no parity error occurs.

In FIG. 11, stations S1 and S4 are both normal, station S4 is abnormal,
This shows the case where S1 is abnormal.

The station identification code D is "0" at the station S1 and "1" at the station S4. First station at time t ₁ S1 "101 is a channel header CH
When the station S4 receives this, the station identification code D is "0", which is the station identification code of the partner station, and
Judges that the data is transmitted by S1, and sets the monitoring bit M to "0".
In addition, the information valid bit V remains “1” and the new header CH _C “0”
001 "is generated and the data is received. The station S4 transmits" 0111 "because the station identification code D of the own station is" 1 ". Therefore, it is determined that the data is correct and received.

Subsequently, the station S1 is to send data, the station S4 is a time t ₂ becomes abnormal, the data S1 is received channel header CH
Will be the same as the value sent. The station S1 determines that the data is incorrect because the received station identification code D indicates its own station, and sets the information valid bit V to "0". So station S1
Does not receive data.

In time t ₃ after the station S1 is abnormal and station S4 is showing the case of normal. The station S4 transmits the channel header CH with “0111” and receives the same data. Since the received station identification code D matches the own station, it is determined that the data is erroneous, the information valid bit V is changed to "0", and no data is received.

Next, an example of one-way transmission will be described with reference to FIG. The station identification code D of the transmitting station S6 is set to “0”.

Time t ₁ from t ₂ is the station S6, S1, S3 all in the case of normal, the station S6
Transmits the channel header CH as “1011”. The first receiving station S1 has a monitoring bit M of "1" and the immediately downstream receiving station flag.
Since DNR is "0", the received information valid bit V is as new information valid bit V _C, and the receive data. The monitoring bit M is changed to "0", and the immediately downstream receiving station flag DNR is set to "1". The receiving station S1 newly transmits "0001" as the channel header CH to the next station.
The second receiving station S3 does not become the immediately downstream receiving station because the monitoring bit M of the received channel header CH is “0”.
Since the information valid bit V is "1", it is received. The same contents as the received channel header are transmitted to the next station.

When the transmission station in S6 now time t ₂ becomes abnormal, data receiving station S3 is transmitted is not updated at the transmitting station S6, the receiving station S1 is receiving the "0001". Since the receiving station S1 is the immediately downstream receiving station, the received monitoring bit M is "0", so that it is determined that the already received data has made two rounds, and the information valid bit V is changed to "0". No data is received.

The next receiving station S3 does not receive because the information valid bit V is "0".

Further, when the receiving station S1 receives the data by making a further round of data, the monitoring bit M and the information valid bit V are "0", so that the immediately downstream receiving station flag DNR is reset to "0".

When the transmission station in S6 the time t ₃ is restored successfully, the transmitting station S6 sends a "1011" as the channel header CH again. The first receiving station S1 receives the data and sets the monitoring bit M to “0”.
Change to The immediately downstream receiving station flag DNR is set to "1" again.

When the receiving station S1 becomes abnormal, the first receiving station S3 becomes the immediately downstream receiving station.

In the transmission 1 shown in FIG. 4, which is 1: 1 one-way transmission,
This corresponds to the case where there is no receiving station S3 in FIG. 12, and the station S1 is always the immediately downstream receiving station.

As described above, in the present embodiment, when the same data circulates, the receiving station does not receive the data but can receive only the correct data.

When the transmission mode is bidirectional transmission using the same channel, the effect of the present invention can be obtained even if a channel header is configured with the parity bit P and the station identification code D.

Further, in the one-way transmission in which the transmission mode is all 1: 1, the effect of the present invention can be obtained even if the channel header is configured by the parity bit P and the monitoring bit M. It is not necessary to determine and set the immediately downstream receiving station.

Further, in the case where the transmission mode is all 1: n polling selection transmission or 1: n broadcast transmission, the effect of the present invention can be obtained even if the channel header is constituted by the parity bit P, the monitoring bit M and the information valid bit V.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to this invention, there exists an effect which can prohibit reception of circulation data by transmission abnormality by providing a channel header and changing determination.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, FIG. 2 is a block diagram of loop transmission, FIG. 3 is a block diagram of a frame flowing on a transmission line in FIG. 2, FIG. 5 is a time chart of the transmission channel of FIG. 4, FIG. 6 is a conventional channel format, FIG. 7 is a transmission configuration diagram showing a conventional transmission system, and FIG. 8 is a channel of one embodiment of the present invention. Format, FIG. 9 is a truth table of the channel header of FIG. 8, FIG. 10 is a circuit diagram of the header decision changing circuit of FIG. 1, FIG. 11 is a bit transition diagram of FIG. 8 in bidirectional transmission, and FIG. FIG. 9 is a bit transition diagram of FIG. 8 in one-way transmission. S1 to S6 station, T1 to T12 terminal, 1 transmission line, CH
... channel header, D ... station identification code, M ... monitoring bit, V ... information valid bit, DNR ... immediately downstream receiving station,
P: parity bit.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masakazu Okada 5-2-1 Omikacho, Hitachi City, Ibaraki Prefecture Inside the Omika Plant, Hitachi, Ltd. (72) Inventor Hiroshi Tomizawa 5-2-2 Omikacho, Hitachi City, Ibaraki Prefecture No. 1 Inside the Hitachi, Ltd. Omika Plant (72) Inventor Nao Ogawa 5-2-1 Omika-cho, Hitachi City, Ibaraki Prefecture Inside the Hitachi Ltd. Omika Plant (72) Inventor Toru Muramoto 5 Omika-cho, Hitachi City, Ibaraki Prefecture Chome 2-1 Hitachi, Ltd. Omika Plant (72) Inventor Seiichi Yasumoto 5-2-1 Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. Omika Plant (72) Inventor Yukio Koyama Hitachi, Ibaraki Prefecture 5-1-1, Hidaka-cho, Hitachi City, Hidaka Works, Hitachi Cable, Ltd. (56) References JP-A-59-21151 (JP, A) JP-A-62 286337 (JP, A) JP-A-62-82745 (JP, A) JP-A-62-82746 (JP, A) JP-A-3-139039 (JP, A) IEICE Technical Report (IEICE Technical Report) Report) Vol. 87, No. 218 IN87-51 Yasuhiro Taki et al .: "Study on slot access method for backbone LAN"

Claims (2)

(57) [Claims] A data transmission between terminals connected to each station by circling a frame composed of a plurality of channels time-division multiplexed on a transmission line connecting a plurality of stations in a ring is fixed to transmission between the respective stations. In a data communication method performed using channels that are temporarily allocated, each of the channels includes a channel header and an information section, and the channel header is provided with a station identification code, a monitor bit, an information valid bit, and a parity bit. The receiving station receives the information part of the channel when the station identification code of the received channel is the station identification code of the transmitting station, and when the monitoring bit set in the transmitting station is set, the receiving station The information part is received and the monitor bit is reset, the information valid bit is set in the transmitting station, and the receiving station receives the information from the station identification code or the monitor bit. When it is determined that the data is normal data and the information of the corresponding channel is not received, the information valid bit is reset at the receiving station, and the receiving station performs a parity check of the channel head of the corresponding channel based on the parity bit and is normal. A data communication method characterized in that a station identification code, a monitoring bit, and an information valid bit are changed only in a data communication system. 2. The data communication method according to claim 1, wherein the station identification codes of the transmitting station and the receiving station have a complement relationship with each other.