JPH01208047A - Clock supplying system - Google Patents

Abstract

PURPOSE:To selectively use the clocks of plural master clock supplying sources by providing a priority clock decision circuit, a clock selector, and a priority data selector. CONSTITUTION:The priority clock decision circuit 1 receives a transmission path clock, an external master clock, and a terminal clock, and compares prior ity data from a transmission path with fixed priority data corresponding to each clock except for the transmission path clock stored in advance. When the priority order of the priority data from the transmission path is higher, a signal for selecting the transmission path clock is supplied to the clock selec tor 2, and the transmission path clock is selected, and also, a priority selector 3 selects and transmits the priority data. When the priority order of the fixed priority data is higher and the decision circuit 1 shows, for example, the exter nal master clock, the external clock and the priority data are sent from the selectors 2 and 3 by the above fact. By employing such constitution, it is pos sible to obtain a synchronous circuit network in which the clock with the highest priority order in the clocks to be inputted to a LAN is set as the master clock.

Description

[Detailed Description of the Invention] [Summary] The purpose of the present invention is to enable clocks from multiple mask clock supply sources to be selected and used in a method of supplying clocks to each communication device of a loop type LAN. , Each communication device has a fixed priority corresponding to the priority data from the transmission path and each clock other than the transmission path clock among the clock input from the transmission path, the clock input from the outside, and the clock input from the terminal. a priority clock determination circuit that determines one of the normal clocks based on the data; and a priority clock determination circuit that determines one of the normal clocks based on the data;
A clock comprising a clock selector that selects the AN clock, and a priority data selector that selects one of the 5S (I priority data) as the priority data to be sent to the transmission line based on the output of the clock determination circuit. Contains a selection device.

[Industrial application field]

The present invention relates to a clock supply system, and particularly to a loop type LAN.
In recent years, LAN (Local Area Network) has come into widespread use, and on the other hand, as networks themselves have become larger, such networks There is a need for a clock that can handle this.

(Prior Art) Conventional clock supply systems in loop-type LANs include an independent synchronous type in which all communication devices (nodes) on the loop (transmission line) have a clock generation source, and a system in which all communication devices (nodes) on the loop (transmission path) are synchronized with the clock of a central device. There is a slave synchronization type in which a signal is sent on a loop and all communication devices on the loop operate in synchronization with a clock extracted from the signal.

FIG. 4 is a diagram showing the former independent synchronous type clock supply system in a LAN.
1, a clock is generated by a clock circuit 12 and applied to a transmitting circuit 13, a data processing circuit 14, a buffer 23, etc., and a signal sent from the center device 10 using this clock is received by a communication device 20 on the loop.

In this communication device 20, the clock of the transmission path is extracted by the clock extraction circuit 22 via the reception circuit 21, and the clock is extracted from the transmission path by the clock extraction circuit 22.
(S circuit) 23. Then, a clock circuit 25 generates a unique clock from an oscillator 24 provided in the communication device 20, and the data stored in the buffer 23 is read out using the clock and sent to the data branching/insertion circuit 26.

This data branching/insertion circuit 26 includes a terminal accommodation circuit 27. which also receives a clock from the clock circuit 25.
~27. (each of these is connected to a terminal (not shown) to exchange data), receives the data, and sends it from the transmitting circuit 28 to a downstream communication device.

Data from the communication device 20 and its downstream communication device (not shown) is received by the reception circuit 21 of the center device 10 , a clock is extracted by the clock extraction circuit 22 and temporarily stored in the buffer 23 , and the data is transmitted from the clock circuit 12 to the reception circuit 21 of the center device 10 . The data is read out by the clock and transmitted from the data processing circuit 14 and the transmission circuit 13, and the same operation as above is repeated.

The fifth circle is a diagram showing the latter slave synchronization type clock supply system. In the center device 10, the external mask clock is received by the PLO circuit 15, and the basic clock is supplied to the clock circuit 1.
2 (however, if there is no external clock, the PLO circuit 15 generates the basic clock), and in each communication device 20, the clock circuit 25 operates in the same manner as above using the basic clock extracted by the clock extraction circuit 22. It differs from independent clock supply systems in that it performs

(Problems to be Solved by the Invention) In the conventional independent synchronization type clock supply system described above, synchronization between terminal devices that perform communication is achieved only between opposing communication devices, and in order to achieve synchronization as a whole, , it is necessary to perform synchronization processing individually between terminal devices, and it is difficult to provide a mask crotter for the entire system.

In addition, in the dependent clock supply method, if the center device itself synchronizes with an external mask clock, the entire LAN is synchronized, and by supplying that clock to the communication device, it is possible to synchronize the entire system. However, due to the expansion of network scale in recent years, multiple LAN or mask clock supply sources as shown in Figs. 6 and 7 exist in a geographically dispersed manner, and it is necessary to select a mask clock supply source according to their status. Therefore, if the entire system is to be synchronized using this slave synchronization type LAN, it is necessary to centrally install the mask crotch supply source and the LAN center device, making it necessary to deal with distributed installation. The problem was that it could not be done.

Therefore, an object of the present invention is to enable clocks from a plurality of mask clock supply sources to be selected and used in a system for supplying clock clocks to each communication device in a loop-type LAN.

[Means to solve the problem]

In the clock supply system according to the present invention, the clock supply source for the LAN is no longer provided only from the center device, but any communication device on the loop transmission path, including the center device, can serve as the clock supply source.

Therefore, in the present invention, as conceptually shown in FIG.
Each communication device on the AN loop supports each clock other than the priority data from the transmission line and the transmission line clock among the clock input from the transmission line, the clock input from the outside, and the clock input from the terminal. a priority clock determining circuit 1 that determines one of the normal clocks based on fixed priority data, and a clock selector 2 that selects one clock as a LAN clock based on the output of the clock determining circuit 1; The clock selection device includes a priority data selector 3 that selects one of the priority data as the priority data to be sent to the transmission line based on the output of the clock determination circuit 1.

[For production]

In the clock supply system according to the present invention shown in FIG. 1, a priority clock determination circuit 1 of a clock selection device in each communication device inputs a transmission path clock, an external master clock, and a terminal clock, and inputs these clocks. Decide which clock to choose between the normal ones within. In making this determination, the priority data received from the transmission path is compared with fixed priority data stored in advance corresponding to each clock other than the transmission path clock.

That is, for example, if the priority data from the transmission line has a higher priority than the fixed priority data, a signal for selecting the transmission line clock is output and given to the clock selector 2. Thereby, the clock selector 2 selects the transmission line clock. The output of this clock determination circuit 1 is also given to a priority data selector 3, which selects priority data from a transmission path and sends it to the transmission path without selecting fixed priority data.

On the other hand, if the − fixed priority data has a higher priority,
If the fixed priority data indicates, for example, an external mask clock, the clock determination circuit 1 generates an output signal indicating this and sends it to the clock selector 2 and the priority data selector 3, and the clock selector 2 outputs an output signal indicating the external mask clock. The clock and the priority data of the external mask clock are respectively sent from the priority data selector 3 to the transmission path.

In this way, a synchronous network can be constructed in which the clocks input to the LAN are masked by high-priority clocks.

〔Example〕

An embodiment of the clock supply system according to the present invention will be described below.

FIG. 2 is a block diagram showing an embodiment of each communication device (including a center device) in the clock supply system of the present invention shown in FIG. 31 is a clock extraction circuit 21.
31 is a PLO circuit, and 32 is a clock circuit that outputs a transmission line clock based on the basic clock from the clock selector 1 and 30. After the clock selected in clock selection 1 and 30 is stabilized by synchronizing the phase with the PLO circuit 31, This is a clock circuit for generating a clock to be sent to a transmission line.

The other configurations are the same as those of the conventional example described above, and the explanation thereof will be omitted.

FIG. 3 is a circuit diagram showing an embodiment of the clock selection device used in the present invention shown in FIG. , clock A is a transmission path clock, and clock B is an external mask clock. In the figure, 41 is a clock disconnection detection circuit;
42 is a clock B disconnection detection circuit, and 43 is priority data indicating the priority from the transmission line (this priority data is inserted into the frame data and is variable as described later). A port register 44 stores a predetermined priority corresponding to the clock B, 45. ~45,1 is n of port register 43
OR gate between the terminal output and the output of the disconnection detection circuit 41, 46
．． ~467 is an OR gate between the n-terminal output of the boat register 44 and the output of the disconnection detection circuit 42, and 47 is an OR gate 45.
．． ~45. The entire output of l and the OR gate 46. These circuits 41 to 47 constitute the priority clock determining circuit 1 shown in FIG. Also, the clock selector 2 is connected to the comparator 4.
The priority data selector 3 selects clock A or clock B according to the output from the comparator 47 and applies it to the PLO circuit of FIG. is selected and sent to the data branch/insertion circuit 26 in FIG.

Next, the operation of the above embodiment shown in FIG. 2 and FIG.
This will be explained using an example of a loop type LAN communication device shown in the figure.

The communication device (2) receives the clock A from the communication device (2) via the loop transmission path, and also inputs the clock B from the mask clock rXB to the priority clock determination circuit 1. If both of these clocks A and B are not in a disconnected state and are normal, the disconnection detection circuits 41 and 42 output, for example, "0".

At this time, the priority data of the transmission line clock and the fixed priority data of the external master clock B are respectively input to the 21 comparator 47 from the port registers 43 and 44.

The comparator 47 selects the smaller input data in advance (
Decide to set the output first, and adjust the output accordingly.
Set to '0'. For example, if the priority data of the transmission line clock from the port register 43 is the priority data of clock B, the transmission line clock is given priority, and the output of the transmission line clock is sent to the clock selector 2 and the priority data selector 3.
I will give it to you.

However, when disconnection is detected by disconnection detection circuits 41 and 42, °'bi is input to OR gates 46 and 47, so the input data to comparator 47 becomes large, and therefore transmission line clock A is not selected. become. This also applies to clock B.

In this way, the transmission line clock A is selected and sent to the communication device (■), and this communication device (■) similarly selects the priority between the transmission line clock A and the terminal clock, and the transmission line clock A is also selected. In this case, this transmission line clock A is compared with the master clock A and the mask clock C in the communication device (2). In this case, since it is necessary to perform two comparisons, two circuits shown in FIG. 3 are prepared. Then, based on the comparison results with the transmission line clock clock A and the transmission line clock clock C, those with higher priority are compared. That is,
When there are two or more clock sources including the terminal clock,
A circuit for sequentially comparing priorities in a tournament manner (
Figure 3) must be prepared. In this case, if the transmission line clock has a higher priority, the port register 43 in FIG.
4 prepares clocks A and C and stores their priority data in advance), so no matter how many clocks there are, the number of circuits in Figure 3 increases, and the clock with the highest priority can be selected. Can be done.

Furthermore, if the transmission line clock A is originally the clock from the master clock rXA, the priority data of both will be the same, so in this case, the comparator 47 determines in advance that it will be "1" degree. Just leave it there.

If priority is given to the transmission line clock, the transmission line clock A will be transmitted through the loop transmission line shown in FIG.

If the mask clock source A stops due to some kind of failure in this state, the communication device (■) that accommodates the mask clock 11E (A) sends a signal to the transmission line based on the clock from the clock C that has the next priority. .Communication device■
In this case, while clock A is being supplied, it operates in synchronization with the clock from the transmission line, but when it detects that it has switched to clock C from the signal from the transmission line, it switches to the clock with higher priority. Send it to the transmission path.

Then, in the communication device (2), since clock B from the transmission path has a higher priority, it switches from clock C to clock B, and this LAN is synchronized with clock B.

In this way, a network can be constructed that is synchronized with the clock with the highest priority among the normal and lock inputs.

This operation is performed in multiple 1. as shown in FIG. , AN can be similarly performed even when connected.

In addition, in the above explanation, if the highest priority clock A is running in a loop and its clock source itself fails and becomes disconnected, that clock A will continue to run. However, as jitter accumulates after passing through the loop several times (several to tens of milliseconds) and data errors occur, clock A is switched to a clock with a lower priority.

〔Effect of the invention〕

As described above, according to the clock supply method of the present invention, each communication device on the loop transmission path receives the transmission path clock,
We have installed a clock selection device that selects the clock with the highest priority among clocks from various clock sources, normal or locked, and sends it to the transmission path, so even if the clock supply sources are dispersed, Network synchronization can be established via a LAN, making it possible to support large-scale networks, and the system has the advantage of being able to easily respond to changes in the clock system by changing priorities.

[Brief explanation of the drawing]

FIG. 1 is a block diagram conceptually showing a clock selection device provided in each communication device (node) in the clock supply method according to the present invention, and FIG. 2 is a block diagram conceptually showing a clock selection device provided in each communication device (node) in the clock supply method according to the present invention. A circuit diagram showing an embodiment, FIG. 3, is a clock IIJ? used in the present invention. 4 is a block diagram showing a conventional independent synchronous loop type T-AN; FIG. 5 is a block diagram showing a conventional dependent synchronous loop type LAN; FIG. 6 is a diagram showing a network configuration with multiple LANs, and FIG. 7 is a diagram showing an example of the configuration of a loop-type LAN in which clock sources are distributed. In FIG. 1, 1...Priority clock determination circuit, 2...Clock selector, 3...Priority data selector. In the figures, the same reference numerals indicate the same or corresponding parts. 2 I Yun Send Fu 71) Things priority data An embodiment of the selection device Fig. 3 A neutral synchronization type] drop type LAN Fig. 4 Dependent synchronous type lub type LAN Fig. 5 Kit work configuration 4 rows Fig. 7

Claims (1)

[Claims] In a method of supplying a clock to each communication device of a loop type LAN, each communication device receives a clock input from a transmission path, a clock input from an external device, and a clock input from a terminal. a priority clock determination circuit (which determines one of the normal clocks based on the priority data from the transmission path clock and fixed priority data corresponding to each clock other than the transmission line clock);
1), a clock selector (2) that selects one clock as the LAN clock based on the output of the clock decision circuit (1), and one of the priority data based on the output of the clock decision circuit (1). a priority data selector (3) for selecting priority data to be sent to the transmission path;
A clock supply method comprising a clock selection device having a clock selection device.