JPH0311701B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a loop type network system that allows information to be transmitted without any trouble even when a transmission line is disconnected.

BACKGROUND OF THE INVENTION An example of a conventional loop type network system is the one disclosed in Japanese Patent Application Laid-Open No. 129048/1983. As shown in Figure 1, for example, three stations A, B, and C are each connected in a loop with a single transmission path, and information is transmitted in one direction of the loop (indicated by an arrow in the figure). It is transmitted only in the counterclockwise direction (as shown).

By the way, in a network system connected in a loop through a single transmission line as described above, if a break in the transmission line occurs, information may be transmitted only in one direction of the loop. Normally, information is no longer transmitted beyond the point of disconnection, causing the entire system to go down.
We use the pool back method to prevent downtime.

This means that, for example, if the transmission line _L3 for transmitting information from station C to station A is disconnected, station A will detect the disconnection of this transmission line _L3 and detect the disconnection of this transmission line _L3 . In addition to informing stations B and C, the necessary information can be transmitted to each station by performing bidirectional communication at predetermined timings such as A→B→C→B→A→B→... This is how it was done.

As shown in Fig. 2, each station (station B is shown as a representative in Fig. 2) is configured to perform loopback processing in the event of a break in the transmission line, as described above. It is equipped with a switch circuit 1 for switching, and when the transmission line is normal, the input line In is connected to the transmission line _L1 from the previous station A so that information is transmitted in one direction of the loop as shown in the figure. connected,
The output line OUT is connected to the transmission line _L2 to the next stage station C.

When a disconnection occurs, the switch circuit 1 is switched at a predetermined timing to switch the transmission/reception direction.

In the figure, CPU2 is a microcomputer that controls communication, SCI (serial
Communication interface) 3 is an interface for inputting and outputting transmission and reception signals,
It has parallel/serial conversion and serial/parallel conversion functions.

ROM 4 and RAM 5 are memories, and interface 6 is an input/output port. An example of a one-chip microcomputer with such a configuration is HD-6801 manufactured by Hitachi.

The structure of the information transmitted in the above network system is, for example, as shown in FIG.
Two channel slots SLT for control data
1, SLT2, and a disconnection information slot SLT3 for notifying disconnection of the transmission line, and the slot SLT3 for sending the disconnection information has an 8-bit configuration.

For example, if a disconnection occurs in the transmission line _L3 between station C and station A,
Since station A does not receive information from station C for a predetermined period of time, the transmission line
It is detected that a disconnection has occurred in _L3 , and from then on, the most significant bit (MSB) of the disconnection information slot SLT3 is
Data with D ₇ as “1”, that is, [10000000]
Data like this, if expressed in binary coded hexadecimal, is
The data of [80H] (H indicates a hexadecimal number) is transmitted to the next stage station B.

At station B, during a period when the transmission line is normal, the contents of the disconnection information slot SLT3 are [00H], but since its MSB is "1", it means that there is a disconnection in the transmission line. , and sends similar disconnection information to station C, and repeats switching of the transmission direction at a predetermined period T ₁ after a predetermined time T _B has elapsed.

Similarly, station C determines that a wire breakage has occurred based on the wire breakage information from station B, and thereafter moves to an operation of repeatedly switching the communication direction at a predetermined period _T1 after a predetermined time T _C has elapsed.

The above operation is schematically shown in FIG. In the same figure, before the wire breakage occurs (before the wire breakage detection time t _O )
In , each station A, B, and C had a constant counterclockwise transmission direction (indicated by L in the figure), but after the time t _O when the disconnection was detected by station A, each station The station has a constant period T ₁
The transmission direction is repeatedly switched between counterclockwise (L) and clockwise (R) to perform bidirectional communication.

In this way, after a break in the transmission line is detected, each station repeatedly switches the transmission line at a constant cycle _T1 , thereby transmitting information to all stations. .

However, as mentioned above, during two-way communication,
If the communication direction switching cycle is set to the same cycle _T1 for all stations, it is impossible to determine whether the information has been received by the destination station. It is necessary to increase the number of data transmissions or to make the switching period of the transmission direction relatively long, which results in a slow transmission speed.

In addition, since the communication direction switching cycle is based on a timer built into each station, variations in the precision of these timers may cause
There is a risk that a difference may occur in the communication direction switching timing for each station, and even if the difference is small at first, it becomes large after a long time, and the communication direction with the adjacent station may become completely opposite. (For example, when the own station is rotating counterclockwise, the adjacent station is rotating clockwise.) In such a case, the deviation in communication direction switching timing due to variations in timer precision becomes even greater, and it becomes impossible to transmit data until the communication direction becomes the same again.

〓Object of the invention〓 This invention was made in view of the above circumstances, and its purpose is to ensure communication reliability when performing loopback type two-way communication after a disconnection occurs in the transmission line. It is an object of the present invention to provide a loop type network system which can improve performance and prevent information transmission from becoming impossible due to any transmission direction switching timing.

〓Configuration of the Invention〓 The configuration of the present invention will be briefly explained below using the claim correspondence diagram of FIG.

As shown in the figure, the loop type network system of the present invention has a configuration in which a plurality of stations are connected in a loop through a single transmission path to transmit information.

Each station is equipped with a disconnection detection means for detecting a disconnection in the transmission line between its own station and the preceding station, and the disconnection information transmitting means detects the disconnection when the transmission line is disconnected. In addition, the timing information transmission means transmits timing information set based on the number of stations from the disconnection point until the disconnection information is received to the next station. do.

Furthermore, when each station receives the disconnection information and timing information, it thereafter switches the transmission and reception direction at a period set to be different from that of the adjacent station based on the number of stations from the disconnection point to the own station. The device is characterized in that it includes a transmission direction switching means.

〓Description of Embodiments〓 Hereinafter, embodiments of the present invention will be described in detail with reference to FIG. 6 and subsequent drawings.

The configuration of the loop type network system of this embodiment is similar to the conventional network system shown in FIG.
C is connected in a loop through a single transmission path. Furthermore, since the configuration of each station is the same as that shown in FIG. 2, FIGS. 1 and 2 are used instead for their configuration diagrams.

FIG. 6 is a flowchart showing the contents of the processing executed in the stations making up the loop type network system of this embodiment. The process shown in the figure is executed by the CPU 2 in FIG.

Below, based on the flowchart shown in the same figure,
Communication control processing of the loop type network system of this embodiment will be explained.

The format of the information transmitted between each station is the same as in the conventional example, as shown in Figure 3.
The frame has a marker slot for frame identification.
Consists of SYN and three data slots SLT1 to SLT3. Among the data slots, SLT
1 and SLT2 are channel slots,
Terminal equipment connected to each station (e.g.
Contains control signal data for headlamps, mirrors, turn signal lamps, etc.).

SLT3 includes 8-bit disconnection information. If there is no abnormality in the transmission path, this is expressed as binary coded hexadecimal data as [00H].
(If expressed in binary, this becomes [000000000])
This is the information.

During the period when the transmission path is normal, each station performs steps (1) → (2) → (3) → (4) in Figure 6.
→(19) →(20) are performed, and information is transmitted only in one direction in a loop (counterclockwise as shown in FIG. 1, as in the conventional example).

In the process of step (1), it is determined whether or not a received signal is input to the SCI 3 based on the state of the SCI 3.

In the process of step (2), the received signal input to the SCI 3 is read into the CPU 2.

In the process of step (3), a process of clearing a soft timer _TM1 for detecting transmission line disconnection, which will be described later, is performed.

In step (4), the SLT in the received data is
3 reads the disconnection information, determines whether “1” is written in the MSB of this SLT3, and if the MSB is “0”, concludes that the transmission path is normal,
If it is other than "0", it is determined that there is a disconnection.

In step (19), processing is performed to set the data of the slot to be transmitted. this is,
This is because the configuration is such that data is transmitted for each slot each time the process shown in FIG. 6 is performed.

In step (20), the data for one slot set in step (19) is output from the SCI 3 to the transmission line.

Next, processing when a disconnection occurs in the transmission line will be explained below in order for each station.

For example, if a disconnection occurs in the transmission line _L3 that transmits information from station C to station A, first, station A will not receive the information from the preceding station C, so step (1) in FIG. ) is NO, and the next step (13) is performed.

In step (13), it is determined whether a flag FLG1 indicating whether or not bidirectional communication using the loopback method is being executed is ON or not.
At station A, at this stage the flag is
Since FLG1 is still OFF, the determination result is
The result is NO, and the next step (14) is processed.

In step (14), processing is performed to advance the soft timer _TM1 for wire breakage detection, and in the next step (15), it is determined whether the contents of the timer _TM1 have exceeded a preset timer time _TO . A determination is made.

Since there is a disconnection in the transmission line _L3 , no information will be transmitted from the station C even after the timer time _TO , so when the timer _TM1 reaches the timer time _TO , Transmission path between previous station C and own station A
It is determined that a disconnection has occurred at _L3 , and the next step (16) is executed.

In step (16), "1" is written in the LSB (least significant bit D _O ) of the slot SLT3 for wire breakage information, and the information is set to [01H] in binary coded hexadecimal notation (H represents hexadecimal notation).

Next, in step (17), a predetermined timer time _T2 is set in the soft timer _T2 that generates the transmission direction switching cycle. After that, step (18)
[01H] is stored in the register _MBRK that stores the disconnection distance (data indicating the number of stations from the disconnection point). This allows station A
In this case, the number of stations on the communication path from the disconnection point is set to 1.

Next, in step (21), a flag indicating that loopback type two-way communication is being executed is set.
Turn on FLG1.

And step (19) and step (20)
Through this process, the transmission data, that is, the two channel slots SLT1 and SLT2 for control, and SLT3 (content is 01H) formed in the above step (16) are transmitted to the next stage station B.

Next, the process from step (1) to step (13) is performed again, and this time, since the flag FLG1 is ON, the process in step (6) is executed next, and the subtraction process of the timer _TM2 is performed. will be done. Then, in step (7), it is determined whether or not the early timer _TM2 is 0, that is, the timer time _T2 has elapsed.
If the execution result is NO, the transmission state is maintained until timer _TM2 becomes 0, and step (19) is performed.
In (20), the above-mentioned transmission data is sent. If the execution result is YES, the timer time T ₂ is set in the timer TM ₂ again in step (8), and then the communication direction is switched in step (9), and T ₂ is set in the switched communication direction. The above transmission data is sent out in steps (19) and (20) for a period of time.

From then on, at station A, step (1)
→(13)→(6)→(7)→(19)→(20)→……(1)→
(13)→(6)→(7)→(8)→(9)→(19)→(20)→……
The process is executed repeatedly.

That is, as shown in FIG.
rotates counterclockwise (from the time t _a when a break in the transmission line between station C and station A is first detected until time T ₂ (the time set in step (17) in Figure 6) has elapsed. L), that is, continue to send out the transmission data of SLT1, SLT2, and SLT3 (content is [01H]) in the direction of station B. After time _T2 has elapsed, the communication direction switches to clockwise (R), and the above transmission data continues to be sent in the direction of station C for the time _T2 (value of timer _TM2 set in step 8). However, in this case, station C cannot receive data due to a disconnection), and as will be described later, the transmitted data sent from station B is received for T ₂ hours (in Fig. 7, during T ₂ , station B cannot receive data). Station A, whose communication direction is counterclockwise (L), cannot receive data, but there will always be cases where it can receive data afterwards). after that,
A switching operation is performed repeatedly to rotate the communication direction counterclockwise (L) and clockwise (R) at a cycle of T ₂ , and transmission and reception are performed in the switched communication direction for a time period of T ₂ .

As described above, station A recognizes that the number of stations from the disconnection point is 1, and starts the timer determined by the number of stations 1 and T ₂ .
The timer time (1×T ₂ ) of TM ₂ is used as the communication direction switching cycle. Also, since the number of stations is 1, the disconnection information SLT3 is set as [01H], and the communication direction is switched every switching cycle T ₂ , and during the switching cycle T ₂ , the switched communication direction is [01H].
I am trying to send transmission data that includes SLT3. Also, if there is transmission data from the preceding station in the switched communication direction, it is received.

Next, station B receives SLT3 whose content is [01H] from station A, and processes steps (1)→(2)→(3)→(4)→(5). The execution result of step (5) is initially
Since the answer is NO, the process of step (10) is performed next.

In step (10), the distance data memory
Processing is performed to store [02H] in M _BRK . This corresponds to the number of stations between the disconnection point and the own station, and it corresponds to the number of stations between the disconnection point and the own station.
A process of adding 1 to the contents of 3 is performed, and the addition result ([02H] in this station B) corresponds to the number of the station from the disconnection point.

Next, in step (11), the contents [02H] of the distance data memory _MBRK are set in the disconnection information slot SLT3 to be transmitted to the next station C.

Then, in step (12), the timer time of the soft timer _TM2 for generating the communication direction switching cycle of the own station is set to the time obtained by multiplying the contents of the distance data memory _MBRK by the reference timer time _T2 . . That is, station B
In this case, the timer time of this timer TM ₂ is 2T ₂
becomes.

After that, the flag is set in step (21).
After turning on FLG1, the transmission data (SLT1, SLT2, SLT3) is sent to the next station C through the processing of steps (19) and (20). The contents of SLT3 are [02H] set in step (11).

After that, when station B receives transmission data from station A (or station C when switching clockwise), it repeats steps (1) → (2) → (3) → (4) → (5).
→ (6) → (7), and when there is no more transmission data from station A, proceed to steps (1) → (13) → (6) →
(7), and continue through steps (19) and 2 until the soft timer _TM2 , which was set to _2T2 in step (7), becomes 0.
At (20), the above transmission data (SLT1, SLT2, SLT3=[02H]) is sent to station C.

Next, when the soft timer TM ₂ becomes 0, the program proceeds from step (7) to step (8), sets the timer TM ₂ to 2T ₂ in step (8), switches the communication direction to the station A direction, and then The above transmission data (SLT3=[02H]) is transmitted until the soft timer _TM2 set to _2T2 becomes 0. At this time, when the station A mentioned above has its communication direction in the direction of the station C, the station A can receive the transmission data from the station B, and as described later, the station C can send the transmission data in the direction of the station B. When sent, station B can receive the content.

_After that, the above transmission data ( _SLT1 , SLT
2, SLT3=[02H]) and receives the transmission data from the previous station in the switched communication direction.

That is, as shown in FIG.
is SLT3 with content [01H] from station A.
The time 2T ₂ from the time _tb when tb is first detected (the timer set in step (12) in
SLT1, _SLT2 , SLT1, SLT2, counterclockwise (L), that is, toward station C, until
Sends the transmission data of SLT3 (content is [02H]). Then, after 2T ₂ hours have elapsed, the communication direction switches to clockwise (R), and the above transmission data is sent in the direction of station A for the time 2T ₂ (value of timer TM ₂ set in step (8)). Along with being sent out,
As will be described later, transmission data sent from station C is received for 2T ₂ hours. after that,
A switching operation is performed to repeat the communication direction from counterclockwise (L) to clockwise (R) at a cycle of 2T ₂ , and transmission and reception are performed in the switched communication direction for a period of 2T ₂ .

As described above, station B recognizes that the number of stations from the disconnection point is 2, and starts the timer determined by the number of stations 2 and T ₂ .
The timer time (2×T ₂ ) of TM ₂ is used as the communication direction switching cycle. Also, since the number of stations is 2, the disconnection information SLT3 is set as [02H], and the communication direction is switched every switching cycle 2T ₂ , and during the switching cycle 2T ₂ , the switched communication direction is [02H].
I am trying to send transmission data that includes SLT3. Furthermore, if there is transmission data from the preceding station in the switched communication direction, it is received.

Next, station C receives SLT3 whose content is [02H] from station B, and performs steps (1)→(2)→(3)→(4)→(5)→(10).
→
The processes of (11) → (12) → (21) → (19) → (20) are executed, and in step (10), the distance data memory
[03H] is stored in M _BRK , and station C
It is remembered that is the third station from the disconnection point. Further, in step (12), _3T2 is set as the timer time of the soft timer _TM2 that sets the communication direction switching cycle.

Then, as shown in FIG. 7, station C detects transmission data from station _B for the first time after _3T2 time (the value of timer _TM2 set in step 12 in FIG. 6) has elapsed. Turn counterclockwise (L), that is, toward station A, until SLT1, SLT2, SLT3 (content is [03H])
After 3T ₂ hours, the communication direction switches to clockwise (R), and the above communication data becomes 3T _2.
time (timer TM ₂ set in step 8)
value), and is sent in the direction of station B. At this time, the transmission data from station A is not received because the transmission line is disconnected. After that, the communication direction is repeatedly switched counterclockwise (L) and clockwise (R) at a time period of 3T ₂ , and in the switched communication direction, 3T ₂
Transmission and reception will be performed every time.

That is, station C is from station B.
When the transmission data with the content of SLT3 is [02H] is received for the first time, step (1)→(2)→(3)→(4)→(5)→(10)
Then, in step (10), 1 is added to [02H] transmitted from station B, and [03H] is set in the distance data memory _MBRK . As a result, station C is set as the third station from the disconnection point. And distance data memory
M _BRK set [03H] in step (11)
Set SLT3, and in step (12) set _3T2 as the timer time of soft timer _TM2 .
Next, in step (21), FLG1, which indicates that bidirectional communication is in progress, is turned on, and in steps (19) and (20), the transmission data (SLT1, SLT2, SLT3 = [03H]) is turned on.
is sent to station A.

Next, after FLG1 is turned ON, if there is transmission data from station B, step (1) → (2) is executed.
→(3)→(4)→(5)→(6)→(7), and if there is no transmission data from station B, proceed to step (1)→
The process proceeds in the order of (13) → (6) → (7), and the above-mentioned transmission data is sent to station A in steps (19) and (20) until the soft timer TM ₂ set to 3T ₂ in step (7) becomes 0. Sends (SLT1, SLT2, SLT3 = [03H]).

Next, when the soft timer TM ₂ becomes 0, the process proceeds from step (7) to step (8), and in step (8), the soft timer TM ₂ is set to 3T ₂ , and the communication direction is switched to the station B direction. Furthermore, the above transmission data (SLT1, SLT2, SLT3 = [03H]) continues until the soft timer TM ₂ set to 3T ₂ becomes 0.
Send out. At this time, the station B mentioned above
When the direction of communication is toward station A, station B receives the above-mentioned transmission data (SLT) sent from station C to station B.
1, SLT2, SLT3 = [03H]) can be received.
_After that, the above transmission data ( _SLT3 =
[03H]) and receives transmission data from the preceding station in the switched communication direction.

As described above, station C recognizes that the number of stations from the disconnection point is 3, and starts the timer determined by the number of stations 3 and T ₂ .
The timer time (3×T ₂ ) of TM ₂ is used as the communication direction switching cycle. Also, since the number of stations is 3, SLT3, which is the disconnection information, is set as [03H], and the communication direction is switched every switching cycle 3T _2. During the switching cycle 3T ₂ , the switched communication direction is set to [03H]. I am trying to send data that includes SLT3. Also, if there is transmission data from the preceding station in the switched communication direction, it is received.

As explained above, in this embodiment, the switching cycle of the communication direction of each station is set to a value different from that of the adjacent station in accordance with the number of stations from the disconnection point, so that the communication direction of the station that sends the transmission data is Even if the communication direction of the next station is different and the next station cannot receive the signal, there will always be a case where the communication direction becomes the same within a short time. For this reason,
Even if the accuracy of the timer time of each station is different, a period in which the communication direction is the same between adjacent stations can be ensured, and data communication can be performed reliably.

Next, in the above embodiment, the communication direction switching cycle at each station is sequentially increased in proportion to the number of stations from the disconnection point. A similar effect can be obtained by performing the process shown in FIG. 8 instead of the process 12).

That is, through the process of step (22), the distance data memory stored in step (10) is
It is determined whether the content of _MBRK is an even number or not, and if it is an even number, the communication direction switching cycle is set to _2T2 by processing in step (24). Furthermore, if the contents of _MBRK are an odd number, the communication direction switching period is set to _T2 by the process of step (23).

As a result, as shown in Fig. 8, the odd-numbered stations A and C from the disconnection point perform an operation to switch the communication direction at a cycle T ₂ from the time they learn of the disconnection, and the even-numbered stations A and C from the disconnection point. At station B, from the time when the disconnection is known, the communication direction is switched at a cycle of _2T2 .

In this way, if two types of communication direction switching cycles are set depending on whether the number of stations from the disconnection point is an even number or an odd number, even if the number of stations configuring the network increases, ,
The communication direction switching cycle is _2T2 at maximum, which can prevent the communication time delay of the entire system from becoming extremely long.

〓Effects of the Invention〓 As explained in detail above, in the loop type network system of the present invention, when performing loopback type two-way communication after a disconnection occurs, information can be reliably transmitted to adjacent stations. and the transmission speed will not become extremely slow.

Furthermore, it is possible to prevent communication with an adjacent station from becoming impossible due to an error in the communication direction switching period for each station.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the system configuration of a loop type network system, Figure 2 is a block diagram showing the hardware configuration of each station, Figure 3 is a diagram showing the format of communication data, and Figure 4 is a diagram of the conventional loop network system. FIG. 5 is a timing chart showing the operation of each station after a disconnection occurs in the loop type network system, FIG. 5 is a diagram corresponding to the claims of the present invention, and FIG. Flowchart showing the contents of processing executed at the station, No. 7
The figure is a timing chart showing the operation after disconnection is detected at each station in the system of the same embodiment.
FIG. 8 is a flowchart showing the main part of the processing executed in each station in another embodiment of the present invention, and FIG. 9 is a timing chart showing the operation after disconnection is detected in each station in the system of the same embodiment. be. A, B, C...Station, _L1 , _L2 , _L3 ...
...Transmission line, SLT3...Disconnection information slot, M _BRK
... Distance data memory, TM ₂ ... Communication direction switching cycle, 1 ... Switch circuit.

Claims (1)

[Claims] 1. In a loop-type network system in which a plurality of stations are connected in a loop through a single transmission path, and information is transmitted only in one direction of the loop while the transmission path is normal. ; Each of the stations is equipped with a disconnection detection means for detecting a disconnection in the transmission line between its own station and the previous station; When a disconnection in the transmission line occurs, the stations sequentially connect to the next station from the station where the disconnection is detected. a disconnection information transmitting means for transmitting disconnection information to notify the occurrence of a disconnection to the disconnection information; together with the disconnection information, timing information that is sequentially set for each station based on the number of stations from the disconnection point until receiving the disconnection information; and a timing information transmitting means for transmitting the information to the next stage station; when the disconnection information and timing information are received, thereafter, based on the timing information,
1. A loop type network system comprising: transmission direction switching means for switching transmission and reception directions at a period set to be different from that of adjacent stations.