JPH03195144A - Clock synchronizing device for ring type local area network - Google Patents

Abstract

PURPOSE:To eliminate necessity for installing a clock source from another network near a central synchronizing node by belonging a clock for transmission at the first terminal housing node to a clock for synchronizing from the other network and setting the clock for transmission as the clock source of a ring. CONSTITUTION:Synchronously with the clock for synchronizing from the other network, a first terminal housing node 10 executes transmission to the ring and by using this reproduced clock, another second terminal housing node 2 executes transmission to the ring. Further, at a normal time, a central synchronizing node 9 uses this clock as a clock for transmitting a frame to the ring and when the first terminal housing node 10 is separated by a bypass, etc., the output of a fixed oscillator provided in the node 10 itself is outputted as a clock for transmission to the ring. Thus, it is not necessary to install the clock source from the other network near the central synchronizing node 9, and a LAN can be belonged and synchronized to the clock inputted from the arbitrary first terminal housing node 10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a clock synchronization device for a ring-type local area network for synchronizing the clock of a local area network with another digital network.

[Conventional technology]

Figure 2 shows, for example, a conventional local area network (hereinafter referred to as LAN) shown in the Information Processing Society of Japan's ``Local Area Network'' Symbosium (September 1988), ``Local Area Network Mr. and Distributed Exchange in LNET''. 1 is a block connection diagram showing a clock synchronization device, in which 1 is a central synchronization node; 2 is a plurality of terminal accommodation nodes connected to a ring together with the central synchronization node; 3 is a transmitter; 4 is a receiver; 6 is a transmission frame generation unit, 6 is a data buffer for matching the phase of the transmission frame 11 between the transceivers 3 and 4, and 7 is a phase-locked loop unit (hereinafter referred to as PLL unit) 28 is a terminal input/output data demultiplexing unit. be.

Next, the operation will be explained. A synchronization clock supplied from another network is input to the PLL section 7 of the central synchronization node 1, and a clock for LAN operation that is frequency-synchronized therewith is generated. The frame generator 5 sends out a frame in synchronization with this clock, and the data buffer 6 relays and multiplexes the received data from the terminal at an appropriate position in the sent frame. The transmission frame created in this way.

The carrier is modulated by the transmitter 3 according to the above clock,
Sent to the transmission path.

On the other hand, the receiver 11 in the terminal accommodation node 1-2 receives the signal from the transmission line and outputs the received data and clock.

The demultiplexing unit 8 separates only the data necessary for the terminal from this received data, and multiplexes the data sent from the terminal to the appropriate position of the transmission frame t1. The transmitter 3 in the terminal accommodating node 2 modulates the transmission data according to the input clock (that is, the clock output by the receiver 4 in the terminal accommodating node 2), and sends the modulated data to the transmission path.

[Problems to be Solved by the Invention] Since the conventional ring-type low-power Lueria network 1-work clock synchronizer is configured as described above, it is possible to synchronize with a clock source that supplies synchronization clocks from other networks and a central synchronization system. There was a problem in that the distance between the node 1 and the node 1 could not be longer than necessary due to the circuit configuration in order to easily obtain the synchronization clock.

This invention was made to solve the above problems, and by inputting a synchronization clock to any terminal accommodation node, it is necessary to install clock sources from other networks near the central synchronization node. It is an object of the present invention to provide a clock synchronization device for a ring type local area network, which can eliminate the clock and synchronize a LAN dependently on the clock from the terminal accommodating node.

[Means to solve the problem]

A clock synchronization device for a ring local area network according to the present invention allows a first terminal accommodation notebook to perform transmission to a ring in synchronization with the frequency of a synchronization clock from another network, and to perform transmission from this ring. The second terminal accommodating node performs transmission to the ring using the clock regenerated from the received signal, and the central synchronization node normally transmits the clock regenerated from the received signal from the ring to the ring. 2. If the first terminal accommodation node is separated by bypass etc. and becomes useless as a clock source for the ring, the output of its own fixed oscillator is output as a clock for transmission to the ring.

[Effect]

The clock synchronization device for a ring local area network according to the present invention subordinates the transmission clock in a first terminal accommodation node to the synchronization clock from another network input to the terminal accommodation node, and The terminal accommodating node performs transmission according to the clock regenerated from the signal transmitted by the terminal accommodating node, and if the terminal accommodating node that inputs the synchronization clock from another network cannot be used as a clock source by bypass etc. If the second node loses the clock that it should follow, detect this unstable state and change the clock for transmission to prevent the LAN and the second node from running unstable. Allows the clock to originate from a fixed oscillator at the central synchronization node.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, 9 is the central synchronization node of the present invention, 10 is the first terminal accommodating node of the present invention, and the second terminal accommodating node that does not input the synchronization clock is the same as the conventional terminal accommodating node 2. used. In addition, 11 is LA whose frequency is synchronized with the synchronization clock supplied from another network.
A PLL section/clock synchronization flag insertion section that generates the clock for N operation and inserts a flag indicating that the clock is in synchronization, and a flag indicating that this is subordinate to the synchronization clock at an appropriate position in the transmission frame. It has the function of establishing 12 is a clock phase difference adjustment buffer; 13 is a clock synchronization determining unit in the central synchronization node 9;
14 is a fixed oscillator; 15 is a transmission clock switching unit that selects one of the transmission clocks from the fixed oscillator 14 and the second terminal accommodation node 2;

Next, the operation will be explained. During normal times.

The first terminal accommodating node 10 reads the transmission data from the clock phase difference adjustment buffer 12 using a clock whose frequency is synchronized with the input synchronization clock, and transmits the data to the first terminal accommodation node 10.
terminal accommodation node] is input to the transmitter 3 in O. As a result, the central synchronization node 9 and the other second terminal accommodating nodes 2 all operate in frequency synchronization with the transmission clock of the first terminal accommodating node 10. At this time, the clock phase difference adjustment buffer 12 uses the clock output from the receiver 4 of the first terminal accommodation node 1o and pr.

The phase difference with the clock output by the L section/clock synchronization flag insertion section 11 is adjusted.

Normally, as described above, the entire LAN operates in dependence on the synchronization clock input to the first terminal accommodation node 10, but this first terminal accommodation node 10 is clocked by a bypass or the like. When the central synchronization node 9 is no longer useful as a clock source, the fixed oscillator 14, which is a fixed clock source provided in the central synchronization node 9, is operated. That is, the central synchronization node 9 is connected to the first terminal accommodation node 1 as described above.
If the clock source from 0 is lost, the receiving transmission frame ls
If synchronization occurs or does not even result in synchronization, the flag indicating clock synchronization sent by the PLL unit/clock synchronization flag insertion unit 11 in the first terminal accommodating node 10 is No longer detected.

Accordingly, the reflock synchronization determining section 13 operates the transmission clock switching section 15 and switches to take in the transmission clock from the fixed oscillator 14 side. As a result,
The entire LAN will operate in dependence on the output clock of this fixed oscillator 14.

In the above embodiment, only one first terminal accommodating node 10 in the LAN inputs the synchronized clock from another network, but if the same frequency-synchronized clock can be input, multiple first terminals can be connected. The accommodating nodes 10 may be connected. In this case, when all the first terminal accommodating nodes 10 are no longer useful as clock sources, the central synchronization node 9 becomes the clock source, and the fixed oscillator 14 The clock will be output from.

〔Effect of the invention〕

As described above, according to the present invention, the first terminal accommodating node performs transmission to the ring in synchronization with the frequency of the synchronization clock from another network, and reproduces the signal received from the ring. The clock is used to cause other second terminal accommodating nodes to transmit to the ring, and the central synchronization node normally transmits a frame to the ring using the clock regenerated from the received signal from the ring. If the first terminal accommodating node is separated by a bypass or the like and becomes useless as a clock source for the ring.

Since the output of its own fixed oscillator is output as the clock for transmission to the ring, there is no need to install clock sources from other networks near the central synchronization node, and any first This has the effect of being able to synchronize the LAN manually with one clock input from the terminal accommodating node.

[Brief explanation of drawings]

FIG. 1 is a block connection diagram showing a clock synchronization device for a ring type local area network according to an embodiment of the present invention, and FIG. 2 is a block connection diagram showing a conventional clock synchronization device for a ring type local area network. 2 is a second terminal accommodation node, 9 is a central synchronization node, 10
is a first terminal accommodating node, and 14 is a fixed oscillator. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. 1st Figure 14: Fixed hole bustle

Claims (1)

[Claims] a first terminal accommodating node that inputs a synchronization clock from another network and transmits to the ring in frequency synchronization with this;
A second terminal accommodating node that transmits to the ring using a clock regenerated from the received signal from this ring, and a second terminal accommodating node that transmits frames to the ring using the clock regenerated from the received signal from the ring in normal times. and when the first terminal accommodating node is separated by a bypass or the like and no longer serves as a clock supply source for the ring, the output of its own fixed oscillator is sent to the ring. A clock synchronizer for a ring local area network, comprising a central synchronization node that outputs a reliable clock.