JPH05227185A - Master station backup system - Google Patents

Abstract

PURPOSE:To back up the master station without fail in the case an abnormality occurs inside and outside the network. CONSTITUTION:A trunk line 281 is connected to a master station MS and a trunk line 282 to a sub master station SMS. At the location of a frame 21 to be sent on a ring type network 20, the first information indicating whether the frame 21 should be sent from a master station MS or from a sub master station SMS and the second information indicating either of the external clock or the internal clock is selected from a trunk line 28 is written. The master station MS and the sub master station SMS are provided with detection means 25, monitoring means 26, and control means 27 to detect whether the frame 21 is normally received and whether the external clock is normal, determining whether serving as a cycle master or being a slave station by monitoring the first and second information.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a master station / submaster station switching system in a ring network.

[0002]

2. Description of the Related Art Conventionally, a network system capable of performing both data transmission by circuit switching and data transmission by packet switching has been proposed, one of which is the American National Standards Institute (ANSI), ANSI X3T9.5 FDDI. HYBRID RING
FDDI (Fiber Distributed) proposed by CONTROL
Data Interface) -2. FIG. 9 is a diagram showing a configuration example of the network, which is a ring type transmission line (hereinafter, simply referred to as a transmission line) 1 composed of an optical fiber, a monitor station MS connected to the transmission line 1, and a slave station SS. Is equipped with. Monitor station M
S can be a cycle master that sends out a frame called a cycle to the transmission line 1, and two or more S are arranged in one network. Slave station SS
Is a relay of a cycle, in which the desired data is taken in from the frame and the data to be transmitted is inserted. In the following, the monitor station MS
And the slave station SS are collectively referred to as a station.

Then, other networks and various devices are connected to each station. For example, in FIG. 9, the monitor station MS ₃ has an ISDN (Integrated Service)
s Digital Network) terminal is connected to a facsimile that supports the G4 system standardized by the International Telegraph and Telephone Consultative Committee (CCITT).
_An ISDN terminal and an Ethernet which is a packet switching network are connected to ₂ , and an external line such as a public telephone line or a dedicated line is connected to the monitor stations MS ₁ and MS ₂ .

FIG. 10 shows the structure of a cycle sent to the transmission line 1. The cycle period is 125 μsec, 125 μs
It includes a preamble part PA indicating the boundary of ec, a cycle header part CH containing control information, and a data part following CH. CH is a starting delimiter SD and cycle control field.
) CC, cyclr sequence C
S, programming template field (prog
Raming template field) PT and IMC. SD indicates the start position of the cycle and is 2
Composed of symbols. A symbol is the minimum unit of data in FDDI-2, and one symbol is 5 bits on the transmission path 1, but is handled by 4 bits inside the station. CC is control information used by the cycle master station to check whether all stations, including its own station, recognize the cycle and are synchronized in the process at startup. And C
_It consists of two fields, ₁ and C ₂ . C ₁ , C
Each ₂ is a symbol. The CS is a field used by the cycle master to identify whether or not the cycle is normally relayed, and is assigned 2 symbols. Specifically, each time the cycle master sends a cycle to the transmission line 1, a predetermined value is set for CS, specifically, 64 _H (H indicates a hexadecimal number, the same applies hereinafter) to 255 _H. Write sequentially. That is, the cycle master has 64 _H for CS in the first cycle and 6 _{H for} the next cycle.
Write and send 5 _H. Note that 64 _H is written again after 255 _H. Therefore, the cycle master can detect whether or not the cycle is normally relayed by recognizing the CS value of the received cycle. The above is the operation in the steady operation state, but in the process at startup, this field is a monitor rank used for a process in which a plurality of monitor stations MS negotiate with each other to determine one station as a cycle master. (Monitor rank) Made as MR. Specifically, it is as follows. As described above, a plurality of monitor stations MS that can be cycle masters are arranged. However, the cycle masters must actually be the ones and the cycle must be sent to the transmission line 1 by only one of them. Therefore, in the start-up process, the monitor stations MS negotiate with each other to determine what becomes the cycle master.
Its Each monitoring station to which priority is set, the monitoring station at the time of start-up processing sends the cycle by writing own priority of (0 _H ~64 _H) to the MR. When the monitor station recognizes from the MR data of the received cycle that there is a monitor station with a higher priority than itself, the monitor station determines to operate as a slave station, and there is no monitor station with a higher priority than itself. When it recognizes, it determines to operate as a cycle master.

The PT is as follows. Cyclic group where data is written following CH (cycl group
ic group) 96 CGs are arranged, but each CG is divided into 16 areas each having a capacity of 2 symbols, and in each area, data of the circuit switching system or packet switching system is stored. Written. Therefore, each CG
It is necessary to clearly define which area is used for circuit switching data and which area is used for packet switching data. A PT is provided for that purpose, and the set S or the reset R is written by the cycle master into P _{0 to} P ₁₅ each having a capacity of 1 symbol. Then, for example, the set S indicates an area used for data of the circuit switching system, and the reset R indicates an area used for data of the packet switching system. Therefore, if the set S is written in P ₀ and the reset R is written in P ₁ , for example, the station receiving this cycle allocates the first area in each CG for the data of the switching line system. It is possible to recognize that the second area is allocated for packet switching system data. P ₂
The same applies to ~ P ₁₅ .

A capacity of 2 symbols is allocated to the IMC, but it is not used in the FDDI-2.

The above is the configuration of CH. Data part is CG
And the Dedicated Packet Data Group (de
dedicated packet data group) DPG. Although the CG is as described above, the DPG is fixedly assigned as being used for data of the packet switching system, and 12 DPGs in total are arranged for every 8CG. The capacity of one DPG is 2 symbols.

FIG. 11 is a functional block diagram showing the configuration of each station. In FIG. 11, a physical medium dependent PMD 11 is shown.
Has a function of converting an optical signal into an electric signal and vice versa.

Physical Layer Protocol (physic
al layer protocol) PHY12 has functions such as conversion from bit stream to symbol, inverse conversion thereof, 4-bit / 5-bit conversion of 1-symbol data, clock extraction, and symbol detection for synchronization. ..

Hybrid ring control (hy
brid ring control) The HRC 13 recognizes the cycle shown in FIG. 10 and multiplexes two kinds of independent data streams in the cycle, that is, a packet-switched data stream and a circuit-switched data stream, It has a distribution function.

Station management
management) The SMT 14 controls each unit and controls the station 10 concerned.
It controls the operation of. Circuit switch multiplexe
r) The CS-MUX 15 performs time division multiplexing and demultiplexing of circuit switched data. The call control 16 controls call connection in circuit switching. Media access control M
AC17 is for media access control for packet switched data. The logical link control LLC 18 performs processing relating to packet exchange data.

Next, an outline of the operation of the station 10 in the configuration of FIG. 11 will be described. In the following description, station 10 is assumed to be monitor station MS. When the power is turned on, the SMT 14 sets the basic mode, and the information of the predetermined priority order is set in the HRC 13
And instruct execution of the startup process. The basic mode is a mode that is set when cycle synchronization is not established, such as when the power is turned on or when an abnormality occurs. In this mode, only the packet switching function operates.

This causes the HRC 13 to cycle MR
Write a priority to and generate a cycle. In this cycle, 4 bits of the symbol are converted into 5 bits by the PHY 12, further converted into an optical signal by the PMD 11, and sent out to the transmission line 1.

The cycle sent from another monitor station MS is received by the PMD 11, converted from an optical signal into an electric signal, and further converted into a 4-bit 5-bit bit stream by the PHY 12 and passed to the HRC 13. The HRC 13 recognizes the MR of the received cycle and compares it with its own priority order, and decides to become a slave if its own priority order is low, but continues the cycle if its own priority order is high. Send out. By repeating the above operation, the monitor station having the highest priority finally becomes the cycle master and starts the transmission of the cycle. At that time, the cycle master decides whether each area of the CG is used for circuit-switched data or packet-switched data,
It is natural to write the set S or the reset R to P _{0 to} P ₁₅ .

When the cycle master is determined as described above, the basic mode shifts to the hybrid mode which is a steady state. The hybrid mode is a mode in which the circuit switching function and the packet switching function coexist.

In hybrid mode, HRC13
Receives the cycle, it refers to the cycle PT,
The circuit switched data is distributed to the CS-MUX 15, and the packet switched data is distributed to the MAC 17. Then, the circuit switching data is transferred from the CS-MUX 15 to the terminal device of the circuit switching system, for example, the ISDN terminal device via the call control 16. Similarly, packet exchange data is transmitted from MAC 17 to L
It is transferred to a terminal device of a packet switching system, for example, an Ethernet terminal device via the LC 18.

Further, when there is a data transmission request from the terminal device of the circuit switching system, the HRC 13 refers to the PT of the received cycle and allocates the data to be transmitted for the CG circuit switching data. In the same manner, when there is a request for data transmission from the packet switching terminal device, the data to be transmitted is written in the area allocated for the CG packet switching data and the cycle is sent out. To do.

In the hybrid mode, the other monitor stations operating as slaves are always
When the cycle master is abnormal due to some cause, it can be detected, and when the cycle master abnormal is detected, the HRC 13 of the station concerned notifies the SMT 14 of that fact. Notice. As a result, the SMT 14 switches the mode from the hybrid mode to the basic mode, the above-described operation is performed again, and the monitor station having the next priority is determined as the cycle master.

[0019]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In I-2, by arranging a plurality of monitor stations MS that can be cycle masters, it is possible to recover when an abnormality occurs in the cycle masters, thereby improving the reliability of the network. Because there are multiple monitor stations,
The following problems may occur.

First, a plurality of monitor stations must negotiate with each other to determine the cycle master, which complicates the control system and increases the number of monitor stations in order to improve reliability. However, there is a problem that the reliability may be reduced against the intention. That is, although the above-mentioned control is logically correct, there is a possibility that the actual circuit may malfunction due to noise, etc. Therefore, the priority order of the monitor stations may match due to some trouble. However, it is doubtful whether a large number of monitor stations can be installed to significantly improve reliability.

Next, there is a problem that system management of the network may be complicated. In other words, when arranging a plurality of monitor stations, which station is to be the monitor station, what priority order each monitor station should have, and the procedure for determining the cycle master are determined. Must be,
System management becomes very complicated and tedious.

Further, since the process of determining the cycle master is performed only between the monitor stations, the station previously defined as the slave station cannot recognize which monitor station is determined as the cycle master. is there. This is especially important in circuit switching systems. That is, in the circuit switching system, it is usual to define one station for centralized channel management, which is shown in FIG.
In the case of the above configuration, it is desirable that it is a cycle master. However, since the slave station cannot recognize which station is the cycle master, it is necessary to inquire which station is the cycle master when transmitting data by circuit switching after the start-up process. Yes, the processing becomes complicated.

Further, the FDDI-2 can cope with an abnormality inside the network, but cannot cope with an abnormality of an external line connected to the station, for example, when an abnormality occurs in the clock of the external line. is there. For example, in FIG.
In the above, it is assumed that the monitor station MS ₁ is a cycle master and an abnormality has occurred in the clock of the external line A in the hybrid mode. At this time, the monitor station MS ₂ is operating as a slave, but when the monitor station MS ₂ is synchronized with the clock of the circuit line B, the cycle master is set to the monitor station MS ₁
It is desirable to change from a monitor station MS ₂ to a monitor station MS ₂ . However, in the FDDI-2, since the cycle master is determined only by the priority order, the cycle master is not changed in response to such an abnormality in the external line. In this case, the monitor station MS ₁ still has the cycle master. Continue to work as. Moreover, at this time, the clock is switched to the internal clock of the monitor station MS ₁ , so that there is no means for synchronizing with the clock of the external line B connected to the monitor station MS ₂ .

On the other hand, in Japanese Patent Laid-Open No. 1-288134, only two stations, a master station and a sub-master station, are arranged as stations that can be master stations capable of transmitting data frames to the network, and external stations are used. It has been proposed to switch the master station from the master station to the submaster station when a clock abnormality is detected. An example of the configuration is shown in FIG.
2 shows the structure of the data frame in FIG.

A master station MS, a sub-master station SMS and a plurality of slave stations SS are connected to the ring type transmission line 1. An external line A is connected to the master station MS and an external line is connected to the sub-master station SMS. B are respectively connected. As shown in FIG. 13, the data frame includes a master function / sub-master function switching control frame MSW, an external clock frame EXTCLOCK, and a data frame DA.
It is composed of TA and control / synchronization frame SV / SYN.

In FIG. 12, the master station MS becomes the master station and the sub-master station SMS becomes the slave station when the power is turned on or the like when the power is turned on. In the steady state, the master station MS becomes MSW "
1 "is written and a data frame is transmitted, and when the sub master station SMS receives the data frame, M
SW is converted to "0" and relayed. Further, the sub master station SMS writes "1" to EXTCLOCK when it is normally connected to the external line B, and EXT when the clock of the external line B is abnormal.
The data frame is relayed by writing "0" in CLOCK.

Then, when the master station MS detects that an abnormality has occurred in the clock of the external line A,
Submaster station SMS has EXTCLOCK = 1
When is displayed, "0" is written in the MSW and the data frame is transmitted. Sub master station S
When the MS recognizes this, it operates the function as a master station.

As a result of the above operation, the sub master station SM will be operated even when the clock of the external line connected to the master station MS becomes abnormal.
Since S functions as a master station, the network can be operated in synchronization with the clock of the external line connected to the sub master station SMS. Further, according to this configuration, since only two stations can be master stations, the above-mentioned problems can be solved.

However, in the system disclosed in Japanese Patent Application Laid-Open No. 1-288134, the master station MS first needs to operate as a master station. However, there is a problem in that the network system cannot be operated when the transmission of the data is not possible.

When an abnormality occurs in the clock of the external line A connected to the master station MS, the master station switches from the master station MS to the sub-master station SMS, but then the clock of the external line A returns to normal, If an abnormality occurs in the clock of the external line B connected to the sub-master station SMS functioning as the master station, the sub-master station SMS is not switched to the master station MS, and the system is restarted. There is also the problem that processing must be performed.

The present invention is intended to solve the above-mentioned problems, and whether an abnormality occurs inside the network or an abnormality occurs in the clock of the external line, either the master station or the sub-master station. It is an object of the present invention to provide a master station backup system that can function as a cycle master.

[0032]

In order to achieve the above object, the master station backup system of the present invention has the configuration shown in FIG. FIG. 1A is a diagram showing the configuration of a network, in which a master station MS, a sub-master station SMS, and a dependent station SS are connected to a ring network 20. Station lines 28 ₁ and 28 ₂ are connected to the master station MS and the sub-master station SMS, respectively. The master station MS and the sub-master station SMS are ring networks 2
0 can be a master that sends out a frame having a predetermined structure, and the dependent station SS communicates using the frame sent out by the master.

In FIG. 1B, the master is the ring network 2.
It is a figure which shows the structure of the frame transmitted on 0, and the frame 21 is provided with predetermined fields 22 and 23. First information indicating whether the frame 21 is transmitted from the master station MS or the submaster station SMS is written in one of the fields 22 and 23, and , The other field contains the master station MS or sub-master station SM
Second information is written indicating whether S is synchronized with the external clock from the office line 28 or with the internal clock. Therefore, for example, when the master station MS sends the frame 21 in synchronization with the external clock, one of the fields 22 and 23 contains information indicating that this frame is sent from the master station MS. Information indicating that the master station MS is synchronized with the external clock from the station line 28 ₁ is written in the other field. The master station MS synchronizes with the internal clock to generate frame 2
The same applies to the case where 1 is transmitted, the sub master station SMS transmits the frame 21 in synchronization with the external clock from the station line 28 ₂ , and the sub master station SMS transmits the frame 21 in synchronization with the internal clock. ..

The master station MS and the sub-master station SMS are
As shown in FIG. 1C, both are detecting means 25 and monitoring means 26.
And a control means 27. The detection means 25 detects whether the frame is normally received and whether the external clock is normal, and the monitoring means 26.
Is for monitoring the first information and the second information. Then, the control means 27 becomes the master and sends out the frame 21 to the ring network 20 or becomes the dependent station and becomes the frame 21 based on the detection result of the detection means 25 and the monitoring result of the monitoring means 26. To determine whether to relay.

[0035]

Embodiments will be described below with reference to the drawings.
The network configuration is as shown in FIG. 2, and similarly to that shown in FIG. 12, a master station MS, a sub-master station SMS, and a plurality of slave stations SS are connected to the ring type transmission line 30. The master station MS is connected to the external line A as a station line of the present invention, and similarly, the sub master station SMS
An external line B as a station line of the present invention is connected to. The master station MS and the sub-master station SMS are the stations that can be the masters that send out the cycle corresponding to the frame of the present invention on the transmission path 30, and the slave station SS has only the function of communicating using the cycle sent by the master. It is equipped with.

FIG. 3 is a diagram showing an example of the structure of the cycle.
In the cycle shown in FIG. 10, the CS field is a synchronous indication field (synchronous).
The indication field) is different only in that it is changed to SI, and the other is the same. SI is a field used by the master station MS and the sub-master station SMS, and has a clock indication (cloc).
k indication) CI and master indication (ma
ster indication) MI is divided. CI and M
Both I are 1 symbol.

The CI indicates whether the master station MS or the sub-master station SMS is synchronized with the external clock or the internal clock. Here, the set S is set when the master station MS or the sub-master station SMS is synchronized with the external clock. Is written, and the reset R is written when synchronized with the internal clock.

MI indicates whether the cycle synchronization is performed by the master station MS or the sub-master station SMS, and here, the set S is set when synchronization is performed by the master station MS. Is written and reset R is written when synchronized by the sub-master station SMS. Therefore, SI is SS
Indicates that the master station MS has transmitted in synchronization with the external clock, and the cycle in which SI is SR indicates the sub master station SMS.
Is transmitted in synchronization with the external clock, the cycle in which SI is RS indicates that the master station MS transmits in synchronization with the internal clock, and the cycle in which SI is RR is , Indicates that the sub-master station SMS has transmitted in synchronization with the internal clock. Here, it is assumed that SS has the highest priority, and SR, RS, and RR are in the following order.

Next, the configurations of the master station MS and the sub-master station SMS will be described. The master station MS and the sub-master station SMS have exactly the same configuration, and although the overall configuration is similar to that shown in FIG. 11, their operations are different.

FIG. 4 is a diagram showing the structure of the HRC.
The C31 includes a cycle transmission / reception unit 32, a timing adjustment buffer 33, a data multiplexing unit 34, a cycle generation unit 35, and a cycle control unit 36.

When receiving the cycle, the cycle transmitting / receiving unit 32 receives the cycle converted from the bit stream to the symbol by the PHY 37 and converts it into byte data, and the data portion of the cycle has the timing adjustment buffer 33.
Then, the cycle header part CH performs a process of transferring to the cycle control part 36. Further, at the time of transmitting the cycle, a process of converting the byte data, which is generated by the cycle generation unit 35 and put in the cycle, into a symbol and transferring the symbol to the PHY 37 is performed.

The timing adjustment buffer 33 is for making the time from transmitting a cycle to receiving the cycle an integral multiple of 125 μsec, which is one cycle of the cycle. The timing adjustment buffer 33 is used for the master station MS and the sub master station SMS.
However, only the one that operates as a cycle master is used.

Regarding data reception, the data multiplexer 34 transfers the switched line data to the CS-MUX 40 and the packet switched data to the MAC 39, respectively, and at the time of data transmission, the switch transferred from the CS-MUX 40. The line data and the packet exchange data transferred from the MAC 39 are multiplexed. Needless to say, the PT of the cycle is referred to when multiplexing and demultiplexing the circuit switched data and the packet switched data.

The cycle generation unit 35 includes a data multiplexing unit 3
A cycle is generated based on the transmission data multiplexed in 4 and a control signal from the cycle control unit 36. The cycle generated by the cycle generator 35 is in the state of byte data.

The cycle control section 36 performs processing such as generation of timing for cycle transmission, or determination of whether to operate as a master or a slave. The detailed configuration and operation of the cycle control unit 36 will be described later.

The above is the configuration of the HRC of the master station MS and the sub-master station SMS. The slave station SS has a configuration excluding the timing adjustment buffer 33.

Next, the structure and operation of the cycle controller 36 will be described. FIG. 5 is a diagram showing a more detailed configuration of the cycle control unit 36 and the flow of various control signals.

The external clock monitoring unit 41 monitors whether or not the clock of the connected external line is normal, and notifies the SMT 38 of the state of the external clock obtained as a result of the monitoring by the external clock status signal. ..

The reception cycle monitoring unit 42 monitors whether or not the cycle is normally received, and notifies the SMT 38 of the cycle reception state obtained as a result of the monitoring by the reception cycle status signal.

The internal clock generator 44 generates an internal clock.

The clock selector 45 includes the external clock from the external clock monitor 41 and the internal clock generator 4.
The internal clock from 4 is input, and based on the clock select signal notified from the SMT 38, the cycle generator 35 is notified of the cycle transmission trigger signal synchronized with either the external clock or the internal clock. The cycle generation unit 35 generates a cycle based on the timing of the cycle transmission trigger signal. Therefore, when the cycle transmission trigger signal is synchronized with the external clock, the cycle synchronized with the external clock is generated and the cycle transmission trigger is generated. If the signal is synchronized with the internal clock, a cycle synchronized with the internal clock is generated.

When the SMT 38 detects that the external clock is normal by the external clock status signal,
The clock selector 45 is notified of the clock select signal instructing the selection of the external clock. Also, when the external clock status signal changes the state of the external clock, that is, when the normal state changes to the abnormal state and when the abnormal state is recovered and returns to normal, and the reception cycle status signal indicates reception of a cycle. When the state changes, that is, when the cycle is not normally received, and when the abnormal reception state is recovered and returns to normal, the HRC state management unit 46 is notified of the reset request signal.

The SI field control unit 43 is based on the station class signal and the clock select signal notified from the SMT 38 and the value of the SI field of the reception cycle notified from the reception cycle monitoring unit 42 during the startup processing. , Whether your own priority is higher than your opponent,
It is detected whether it is low, and based on that, the master standby status signal is notified to the HRC state management unit 46, and the transmission SI status signal is notified to the cycle generation unit 35. here,
The station class signal is a signal indicating whether it is defined as the master station MS, the sub master station SMS, or the slave station SS in advance. In the master station MS, S is , R is notified in the sub master station SMS. The master standby status signal is a signal indicating whether the value of the SI field of the received cycle is higher or lower than that of its own, or whether the received cycle is the cycle which it previously sent. The transmission SI status signal is a signal indicating the value of the SI field of the transmission cycle.

The HRC state management unit 46 receives a reset request signal, a cycle start signal,
Station class signal and SI field control unit 4
3 based on the master standby status signal notified from 3 and the reception CC status signal notified from the reception cycle monitoring unit 42, a cycle action signal for instructing whether the cycle is transmitted or not is generated.
Notify 5. Here, the received CC status signal is used to detect whether or not the synchronization of all stations including self is established.

The above is a general description of the operation of each part of the cycle control unit 36. Next, regarding the operation for determining the cycle master during the start-up process, H shown in FIG.
FIG. 7 and FIG. 8 showing the state transition of the RC state management unit 46.
The state transition of the SI field control unit 43 shown in FIG.

When power is turned on or when an abnormality occurs in the network system, the SMT 38 notifies the HRC state management unit 46 of a reset request signal. As a result, the HRC state management unit 46 transitions to the basic state shown in FIG. In this state, only the packet switching function operates. In this state, when the SMT 38 designates a predetermined class by the station class signal and the cycle start signal issues a cycle transmission request (S1 in FIG. 8), the HRC state management unit 4
6 notifies the cycle action signal to the cycle generation unit 35 to instruct the transmission of the cycle, and the CM (cycle master) standby state of FIG.
S and sub master station SMS are cycle masters C
Transition to a state to negotiate to determine M. As a result, the cycle generation unit 35 generates and sends a cycle in synchronization with the cycle transmission trigger signal by the cycle action signal. The SI field value of the cycle transmitted at this time is determined by the SI field control unit 43 based on the station class signal and the clock select signal notified from the SMT 38, and notified to the cycle generation unit 35 by the transmission SI status signal. To do.

The operation of the SI field control unit 43 will be described below. The SI field control units 43 of the master station MS and the sub-master station SMS both have three types of inactive (Inactive), external active (Active-Ext), and internal active (Active-Int) as shown in FIGS. It has three states, but behaves differently. Note that inactive is a state in which it operates as a slave, and is in this state at the time of initialization. The external active is a state in which the cycle is transmitted in synchronization with the external clock, and the internal active is a state in which the cycle is transmitted in synchronization with the internal clock.

Now, the SI field control unit 43 of the master station MS, in the inactive state,
When it is detected that the external clock is selected by the clock select signal, the state transits to the external active state (S10 in FIG. 7), and when it is detected that the internal clock is selected, the state transits to the internal active state (S1).
1). In the inactive state, the sending SI status signal indicates the contents of the receiving SI status signal, and the master standby status signal indicates that the value of the SI field has a higher priority than self.

When the SI field control unit 43 detects that the external clock is selected by the clock select signal in the internal active state, the SI field control unit 43 transits to the external active state (S12), but the received SI
When the status signal detects that the cycle in which the SI field value is SR is received, the status returns to the inactive state (S13). That is, in the internal active state, the value of the SI field of the master station MS is RS, while the sub master station S
When the MS selects the external clock and is transmitting a cycle, the value of the SI field of the cycle is SR, and the master station MS stops becoming the cycle master due to the above priority. In addition,
In the internal active state, the sending SI status signal indicates RS, and the master standby status signal indicates that when the receiving SI status signal is RR, the value of the SI field has a lower priority than that of the receiving SI status signal.
When the I status signal is RS, it indicates that the value of the SI field matches its own priority.

Further, when the SI field control unit 43 detects that the internal clock is selected by the clock select signal in the external active state, the SI field control unit 43 transits to the internal active state (S14). In the external active state, SS is indicated as the transmission SI status signal, and the master standby status signal is SI when the reception SI status signal is RR or SR.
The value of the field has a lower priority than that of the self, and when the reception status signal is SS, it means that the value of the SI field matches the priority of the self.

The SI field control unit 43 of the sub master station SMS, in the inactive state,
When it is detected that the external clock is selected by the clock select signal, the state transits to the external active state (S15 in FIG. 8), and when it is detected that the internal clock is selected, the state transits to the internal active state (S1).
7). In addition, in the inactive state, the transmission SI
The status signal indicates the content of the received SI status signal, and the master standby status signal indicates that the SI field value has a higher priority than self.

The sub master station SMS S
When the I-field control unit 43 detects that the external clock is selected by the clock select signal in the internal active state, the I-field control unit 43 transitions to the external active state (S18), but the SI field value is changed by the received SI status signal. When it is detected that the SS or RS cycle is received, the state returns to the inactive state (S19). That is, in the internal active state, the value of the SI field of the sub master station SMS is RR, and if the master station MS is operating normally regardless of whether it is synchronized with the internal or external clock, The higher priority,
The submaster station SMS ceases to be a cycle master. In the internal active state, the transmission SI status signal indicates RR, and the master standby status signal indicates that the SI field value matches its own priority when the reception SI status signal is RR.

Also, the S of the sub master station SMS
In the external active state, the I-field control unit 43 transitions to the inactive state (S19) when it detects that the SI field has a value of SS in the cycle received by the received SI status signal (S19). When it detects that the internal clock is selected, it transits to the internal active state (S2
0). In the external active state, the transmission SI
The status signal indicates SR, the master standby status signal indicates that the SI field value has a lower priority than self when the reception SI status signal is RS, and the SI standby signal indicates SI when the reception SI status signal is SR. Indicates that the value of the field matches its own priority.

The above operations are performed in the SI field control units 43 of the master station MS and the sub master station SMS to generate a master standby status signal and a transmission SI status signal.

In the CM standby state, the HRC state management section 46 determines the CM (cycle master) when the reception cycle is the cycle transmitted by the local station according to the master standby status signal from the SI field control section 43. Although it transits to the standby state (S2 in FIG. 6),
When the value of the received SI field is higher than the priority of the own station, it transits to the SL (slave) operation state (S
3), it operates as a slave station. If the received SI field value is lower than the priority of the own station, the CM standby state remains.

When the HRC state management unit 46 in the CM standby state detects that the synchronization of all stations has been established by the reception CC status signal notified from the reception cycle monitoring unit 42, the HRC state management unit 46 enters the CM operation state. Transition (S
4) The operation as a cycle master is started.

When the HRC state management unit 46 is in the CM operating state, in the CM standby state, and in the CM standby state, when the reset request signal is notified from the SMT 38, S5 of FIG. , S6, S7
As shown in, the operation returns to the basic state, the above-mentioned operation is performed again, and a cycle master is newly determined. For example, if an abnormality occurs in the external clock of the master station MS when the master station MS is now in a steady operation state as a cycle master, the SMT 38 of the master station MS will receive an external clock status signal from the external clock monitoring unit 41 to externally A clock abnormality is detected, and a reset request signal is sent to the HRC state management unit 4
Notify 6. As a result, the HRC state management unit 46 transits to the basic state and stops the cycle transmission. When the cycle on the transmission path disappears, the SMT 38 of each station including the sub master station SMS detects an abnormality in the reception cycle by the reception cycle monitoring unit 42 and notifies the HRC state management unit 46 of a reset request signal. As a result, the HRC state management units 46 of all stations transit to the basic state.

The SMTs 38 of the master station MS and the sub-master station SMS send a cycle start signal to the HRC state management unit 46 after the time required for the HRC state management units 46 of all stations to transit to the basic state. Notify and request cycle transmission. The HRC state management unit 46 of the master station MS and the sub master station SMS transits to the CM standby state again (S1) and monitors the master standby status signal from the SI field control unit 43. At this time, the SMT 38 of the master station MS has already detected the abnormality of the external clock and has selected the internal clock by the clock select signal. Therefore, the state of the SI field control unit 43 changes from the external active state to the internal active state. The SI of the cycle that transits (S14 in FIG. 7) and is transmitted
The value of the field will be RS. When the SMT 38 of the sub master station SMS selects the external clock by the clock select signal, the state of the SI field control unit 43 is external active as shown in FIG. Value is SR
become.

Therefore, when the SI field control unit 43 of the master station MS receives the cycle in which the value of the SI field is SR, it transits to the inactive state (S13), and the priority of the received SI field is given by the master standby status signal. Is notified to the HRC state management unit 46. Upon receiving it, the HRC state management unit 4
6 shifts to the SL operation state (S3 in FIG. 6) and operates as a slave station. On the other hand, when the SI field control unit 43 of the sub master station SMS receives the cycle in which the SI field value is SR, the HRC state management unit 46 informs that the SI field value matches the own station value by the master standby status signal. To notify. After that, the HRC state management unit 46 of the sub master station SMS transitions to the CM standby state, transitions to the CM operation state when recognizing that the synchronization of all stations is established, and starts the operation as the cycle master.

However, when the abnormality of the external clock of the master station MS is recovered thereafter, the HRC state management unit 46 of the master station MS is reset again, the above-described operation is performed, and this time, the master station MS.
Is determined as the cycle master.

The operation when the master station MS operates as a cycle master and an abnormality occurs in the external clock has been described above. When the sub master station SMS operates as a cycle master, the external clock abnormality occurs. In the case of occurrence of the above, the same operation is performed, and one having a higher priority than either the master station MS or the sub master station SMS is determined as the cycle master. Similarly, the reset request signal is notified from the SMT 38 even when the cycle cannot be received normally and when the abnormal state of the reception cycle is recovered. Therefore, the cycle master is determined each time by the above-described operation. Is.

The above is the processing of the cycle control unit 36 of the master station MS and the sub-master station SMS. If the external clock or the reception cycle becomes abnormal due to the execution of the above processing, or the abnormal state thereof. It will be apparent that the cycle master is determined each time the is restored.

Although not essentially related to the present invention, the operation of a station which is predetermined as the slave station SS is as follows. When the HRC state management unit 46 of the slave station SS receives a cycle in the basic state, the HRC state management unit 46 directly transits to the SL operation state (S8 in FIG. 6) and operates as a slave, and SL
When the reset request signal is received from the SMT 38 in the operating state, the operation of returning to the basic state is repeated. Note that the station operating as a slave may change the value of MI in the SI field of the cycle transmitted by the cycle master.
It is possible to recognize whether the master station MS is the cycle master or the sub master station SMS is the cycle master.

Although one embodiment of the present invention has been described above, it is obvious to those skilled in the art that the present invention is not limited to the above embodiment and various modifications can be made.

[0075]

As is apparent from the above description, according to the present invention, since only two stations can transmit a frame to the ring network, the backup processing of the master station can be performed as compared with the conventional case. It will be easier and more reliable. For backup processing, the first information indicating whether the frame is transmitted from the master station or the sub-master station is provided at a predetermined position of the frame to be transmitted on the ring network. Since a simple operation of describing the second information indicating whether the frame is synchronized with the external clock or the internal clock from the central line is performed, the mounting amount of hardware and software is significantly reduced. Can be made

Further, even if an abnormality occurs in the station line, it can be surely backed up, and in the event of a failure in either the master station or the submaster station, it can be automatically returned to the operable state. You can Furthermore, by a simple process of detecting the first information and the second information, all stations recognize which station is currently transmitting a frame and whether they are synchronized with an external line. Is what you can do.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of the present invention.

FIG. 2 is a diagram showing a configuration example of a network according to an embodiment of the present invention.

FIG. 3 is a diagram showing a structural example of a cycle transmitted in the present invention.

FIG. 4 is a diagram showing a configuration example of an HRC in one embodiment of the present invention.

5 is a diagram showing a detailed configuration example of a cycle control unit shown in FIG.

6 is a diagram showing state transition of the HRC state management unit shown in FIG.

7 is a diagram showing state transitions of the SI field control unit shown in FIG.

8 is a diagram showing state transitions of the SI field control unit shown in FIG.

FIG. 9 is a diagram illustrating a configuration example of an FDDI-2 network.

FIG. 10 is a diagram showing a structure of a cycle of FDDI-2.

FIG. 11 is a functional block diagram showing the configuration of each station.

FIG. 12 is a diagram showing a configuration example of a network disclosed in Japanese Patent Laid-Open No. 1-288134.

FIG. 13 is a diagram showing a structure of a data frame used in FIG.

[Explanation of symbols]

20 ... Ring type network, 21 ... Frame, 22,
23 ... Field, 25 ... Detection means, 26 ... Monitoring means,
27 ... Control means, 28 ... Station line, MS ... Master station, SMS ... Sub master station, SS ... Slave station.

Claims (1)

[Claims] 1. A ring-type network in which a master station and a sub-master station to which a station line is connected and a subordinate station that communicates using a frame transmitted by the master station or the sub-master station are connected. At a predetermined position, the first information indicating whether the frame is transmitted from the master station or the submaster station, and whether the frame is synchronized with the external clock or the internal clock from the station line A field in which second information indicating whether or not there is is written is provided, and the master station and the sub-master station both detect the presence or absence of abnormality of the received frame and external clock; Means for monitoring the information and the second information, and controlling the transmission of the frame based on the detection result and the monitoring result Master station backup method, characterized in that it comprises a control means.