JPH02149045A - Communication system - Google Patents

Abstract

PURPOSE:To put a self-running function into operation, and to make an exchange execute communicating operation by a clock it has for itself even in the case of an unstable network clock by stopping the sending of the clock to the exchange from a station when the clock sent from the station to the exchange is unstable. CONSTITUTION:This system is constituted of loop-shaped communication network 1 connected to wide area network through the exchange 2, and in the communication network 1, plural stations 5... are connected into the form of a loop through a transmission line 4. When the control of the restoration of trouble due to the abnormality of the transmission line 4, the station 5, etc., is executed, a network clock CLK becomes unstable temporarily. On the other hand, when the station 5 recognizes that the network clock CLK becomes unstable temporarily, the CPU 14 of the station 5 outputs an OUT instruction to make a data signal through a data line 12 into 'H'. Accordingly, an output line 22 becomes 'H', and a gate circuit 8 is turned OFF, i.e., signal lines 9 and 10 are disconnected, and in the exchange 2, the supply of the network clock CLK comes to be stopped for over predetermined time, and the system comes to start self-running.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to, for example, a loop type communication system.

(Prior Art) In recent years, there has been a strong demand for integrating independent and scattered communication networks to construct an organic network system.

FIG. 2 is a diagram showing an example of such a communication system, which is connected to a wide area network 3 via a loop-type communication network 1 or an exchange 2. In FIG.

In the communication network 1, a plurality of stations 5 and 5 are connected via a transmission path 4.
... are connected in a loop. Each station 5 includes a transmission line side interface unit 6 for exchanging signals with the transmission line 4, an exchange side interface unit 7 for exchanging signals with the exchange 2, and the like. Further, this communication network 1 receives a network clock CLK from an exchange 2 connected to the wide area network 3 in order to perform communication in synchronization with the wide area network 3 . That is, the station 5 supplied with the network clock CLK passes this network clock CLK to the transmission line 4.

Each station 5... has a network clock CL supplied from the transmission line 4.
K is delivered to exchange 2 connected to the own station.

By the way, the exchange 2 receives the network CLK from the transmission line 4.
In preparation for when the supply of network clock CLK is stopped, the network clock CLK
It is designed to become self-propelled when there is a supply outage.

However, if the network clock CLK is unstable and does not stop completely, this self-running function may not operate.

For example, if the transmission line 4 is a loop type, fault recovery control is performed due to an abnormality in the transmission line 4, station 5, etc., and the network clock CLK becomes unstable at times, causing the output and stop of the network clock CLK to change. may be repeated.

Exchange 2 receiving network clock CLK from transmission path 4
As mentioned above, when the supply of the network clock CLK is stopped for a predetermined period of time or more, the network clock CLK is designed to run on its own.
If the vehicle is unstable, the self-propelling function will not work.

If the self-running function does not operate even though the network clock CIJ is unstable as described above, there is a risk that not only an abnormal operation will occur in the exchange 2, but also that this abnormality will spread to the entire system. There is also.

(Problem to be Solved by the Invention) In a communication system in which a communication network is connected to a wide area network and each station in the communication network receives the network clock, the exchange connected to the station receives the network clock. In preparation for when the network clock supply is stopped, the clock has a self-running function, and when the network clock supply is stopped for a predetermined period of time, the clock starts running automatically, but the network clock is unstable. If the switch does not completely stop, the self-propelled function may not operate, which may cause malfunction of the exchange, and furthermore, this malfunction may spread to the entire system.

Therefore, an object of the present invention is to realize a communication system in which the self-running function operates even when the network clock is unstable.

[Configuration of the Invention (Means for Solving the Problems) This invention consists of a station that is connected to a transmission line and performs a communication operation in synchronization with a clock transmitted from the transmission line, and a station that is connected to this station and that An exchange that performs communication operations in synchronization with a clock sent out from the station, and when the clock sent out from this station stops for a predetermined period of time or more, an exchange that performs communication operations using its own clock; The above-mentioned problem is solved by providing means for stopping the transmission of the clock from the station to the exchange when the clock being transmitted is unstable.

(Function) In other words, in this invention, when the clock sent from the office to the exchange is unstable, the sending of the clock from the office to the exchange is stopped, so that the exchange performs communication operations using its own clock. I will do it.

(Example) Next, the present invention will be explained in detail.

FIG. 1 is a diagram for explaining one embodiment of the present invention, and shows a partial configuration of a station 5 and a partial configuration of an exchange-side interface section 7 shown in FIG.

In FIG. 1, reference numeral 8 denotes a gate circuit that switches whether or not the network clock CLK sent from the transmission path 4 via the signal line 9 is introduced into the exchange 2 via the signal line 10. That is, in this gate circuit 8, "L" is input to the switching signal input terminal.
When a signal of "H" is input manually, the signal line 9 and the signal line 10 are connected, and when a signal of "H" is input, the signal line 9 and the signal line 10 are disconnected.

Further, 11 is a small circuit consisting of a D flip-flop and a controller for controlling switching of the gate circuit 8.

A D terminal of this control circuit 11 is connected to a data bus 13 via a data line 12. Therefore, the CPU
A data signal outputted from the control circuit 14 is taken into the control circuit 11 from the D terminal via the data bus 13 and the data line 12.

The CLK terminal is connected to clock line 15. This clock line 15 is connected to an output terminal of an OR gate 16. One input terminal of the OR gate 16 is connected to an address bus 18 via a decoder 17, and the other is connected to an I10 write line 19.

This I10 write line 19 is directly connected to the CPU 14. Therefore 1. A chip select signal output from the CPU 14 is input to one input terminal of the OR gate 16 via the address bus 18 and the decoder 17. In addition, the I10 write signal output from the CPU 14 is
The signal is input to the other input terminal of the OR gate 16 via the 10 write line 19.

The OR gate 16 connects these chip select signals and I10.
A clock signal is generated based on the write signal. This clock signal is taken into the control circuit 11 from the CLK terminal via the I10 write line 19.

The CLR terminal receives Rc s c from the CPU 14 as a signal 20, and the control circuit 11 is reset together with the reset of the CPU 14.

The Q terminal is connected to an output line 22 led out to a switching signal input terminal of the gate circuit 8.

Next, the operation of this embodiment will be explained.

For example, when failure recovery control is performed due to an abnormality in the transmission line 4, station 5, etc., the network clock CLK becomes unstable over time. On the other hand, when such failure recovery control is performed, the station 5 is naturally included in the control target. Therefore, station 5 temporarily loses network clock C from these control commands.
It can be seen that LK becomes unstable.

When the station 5 recognizes that the network clock CLK is temporarily unstable, the CPU 14 of the station 5 changes the data signal via the data line 12 to "H" in response to the address of the control circuit 11. Outputs an OUT command like this. Therefore, the output line 22 becomes H'', and the gate circuit 8 is turned off, that is, the signal line 1 and the 1= line 10 are disconnected.

As a result, the supply of the network clock CLK will be stopped at the exchange 2 for a predetermined period of time.
Becomes self-propelled.

In other words, in this embodiment, even if the network clock CLK is unstable and does not completely stop, the self-running function is activated and prevents an abnormal operation of the exchange 2 or a system abnormality caused by this abnormality. be done.

[Effects of the Invention] As explained above, according to the present invention, when the clock sent from the office to the exchange is unstable, the transmission of the clock from the office to the exchange is stopped, so that the network clock is The self-propelling function is also activated in the event of instability.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a gate control circuit according to an embodiment of the present invention, and FIG. 2 is a diagram showing a communication system in which a communication network is connected to a wide area network via an exchange. 1...Communication Wattnake, 2...Switchboard, 3...
wide area network, 4... transmission line, 5... station, 8... gate circuit, 11... control circuit. Applicant Toshiba Corporation Patent Attorney Sasa Suyama - Figure 1

Claims (1)

[Claims] (1) A station that is connected to a transmission path and performs communication operations in synchronization with a clock sent out from this transmission path, and a station that is connected to this station and performs communication operations in synchronization with a clock sent out from this station. , when the clock sent from this station stops for a predetermined period of time or more, the exchange performs communication operations using its own clock, and when the clock sent from the station to the exchange is unstable, the exchange from the station to the exchange A communication system comprising means for stopping transmission of a clock.