JP2001238281A - Digital network synchronization method and digital network synchronization system adopting the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a digital network synchronization system with a small scale and a simple configuration that can take network synchronization of an entire system while eliminating the need for a network clock transmission line. SOLUTION: In this system, a network synchronization unit (specific master unit) 201 among network synchronization units 201-20n connected to a system transmission line S1 and a digital data transmission line S2 uses as idle time slot of a digital data signal sent through the transmission line S2 to generate a network clock signal denoting a master network clock and transmits it to the transmission line S2, and a DPLL 10a of a DPLL mount unit 10 enervates a system clock signal synchronized on the basis of the network clock signal from the transmission line S2 and transmits it to the transmission line S1 so that the system clock signal is sent to the network synchronization units 201-20n and the network synchronization of the entire system connected to the transmission line S1 can be taken as a result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital network synchronization system mainly applicable to a digital key telephone system, and more particularly to a digital data transmission line (usually a PCM) by eliminating a network clock transmission line. The present invention relates to a digital network synchronization method for synchronizing the entire system using empty time slots of a digital data signal transmitted on a highway (referred to as a highway), and a digital network synchronization system having a small-scale configuration to which the method is applied.

[0002]

2. Description of the Related Art Conventionally, in this kind of digital network synchronization method, a network clock in which a specific master unit among a plurality of network synchronization units connected and arranged as an interface unit by applying ISDN or the like becomes a master network clock. Is extracted from the digital network and sent to the network clock transmission line as a network clock signal.
The L mounting unit receives the network clock signal from the network clock transmission line, generates a synchronized system clock signal based on the network clock, and sends the system clock signal to the system clock transmission line. Network synchronization of the entire system is achieved by the connected DPLL mounting unit and a plurality of network synchronization units.

FIG. 3 is a block diagram showing a basic configuration of a digital key telephone system according to an example of a conventional digital network synchronization system to which such a digital network synchronization method is applied.

In this digital key telephone system, a system clock transmission line S1 for transmitting a system clock signal synchronized with a master network clock is transmitted to a digital data signal for exchanging digital data such as time-division voice data. Data transmission line S2 which is a path, a network clock transmission line S3 to which a network clock signal indicating a master network clock is exclusively transmitted, and a system clock transmission line S1 as an interface unit with each other by application of ISDN or the like. The digital data transmission line S2 is selectively connected to the digital data transmission line S2 and the network clock transmission line S3, and the digital network DN and the system clock transmission line S1,
A network clock signal, which is connected to each of the digital data transmission line S2 and the network clock transmission line S3 and indicates a master network clock extracted from the digital network DN, is transmitted to the network clock transmission line S3, and is used for digital data transmission. Line S
2, a specific master unit for transmitting and receiving digital data signals via the system clock transmission line S1 and the system clock transmission line S1 connected to the system clock transmission line S1 and the digital data transmission line S2,
And a plurality of network synchronization units 30 ₁ to 30 _n including at least one general-purpose unit for transmitting and receiving digital data signals via the digital data transmission line S2, a system clock transmission line S1, a digital data transmission line S2, and A DPLL 10a 'which is connected to the network clock transmission line S3 and generates a synchronized system clock signal based on the network clock signal transmitted from the network clock transmission line S3 and outputs the system clock signal to the system clock transmission line S1; And a DPLL mounting unit 10 'for transmitting and receiving a digital data signal via a digital data transmission line S2.

Namely, in this digital key telephone system, the network synchronization unit 30 _one of the plurality of network synchronization unit 30 ₁ to 30 _n has a particular master unit and extracts the master network clock from the digital network DN And sends it to the network clock transmission line S3 as a network clock signal,
The network clock signal from the network clock transmission line S3 is
For each network synchronization unit 30 ₁ to 30 _n by sending and receiving the 'DPLL10a of' PLL mounting unit 10 generates a synchronized system clock signal on the basis of the network clock signal to the system clock for transmitting line S1 As a result, the DPLL mounting unit 1 connected to the system clock transmission line S1 is transmitted.
0 'and the network synchronization of the entire system of the respective network synchronization unit 30 ₁ to 30 _n are adapted to be taken.

[0006]

In the case of the above-mentioned digital network synchronization system (digital key telephone system), D
A system clock transmission line, a digital data transmission line, and a network clock transmission line are connected to the PLL mounting unit and a specific master unit of the network synchronization unit. A digital data transmission line is connected to the synchronization unit, and a master network clock extracted from the digital network by a specific master unit is sent out as a network clock signal to the network clock transmission line, and the DPLL mounting unit D
The result that the system clock signal is transmitted to each network synchronization unit by the PLL generating the synchronized system clock signal based on the network clock signal from the network clock transmission line and outputting it to the system clock transmission line In this configuration, network synchronization of the entire system is achieved. In such a configuration, network synchronization of the entire system is performed with respect to the DPLL mounting unit and a specific master unit of the network synchronization unit. Since it is necessary to connect a dedicated network clock transmission line, the wiring connection of the entire system is not complicated and the scale is not avoided, and the digital data connected to the PLL mounting unit and each network synchronization unit as a PCM highway This part is effectively used even though there are empty time slots in the digital data signal transmitted and received on the transmission line. Because they are not rationally there is a problem that it can not synchronize the overall system network.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem. A technical problem of the present invention is to eliminate a network clock transmission line and to rationally synchronize a digital network with the entire system. It is an object of the present invention to provide a synchronization method and a digital network synchronization system which can be configured in a small scale and simply by applying the synchronization method.

[0008]

According to the present invention, a digital data for exchanging time-divided digital data by a specific master unit of a plurality of network synchronization units connected and arranged as an interface unit to each other is provided. Using a vacant time slot of the digital data signal transmitted to the digital data transmission line, which is a signal transmission path, to generate a network clock signal indicating a master network clock and transmitting the network clock signal to the digital data transmission line; The mounting unit receives the network clock signal from the digital data transmission line, generates a synchronized system clock signal based on the network clock signal, and sends the synchronized system clock signal to the system clock transmission line. A system comprising the DPLL mounting unit and the plurality of network synchronization units connected to a transmission line. Digital network synchronization method characterized by Temu entire network synchronization is obtained.

Further, according to the present invention, a system clock transmission line for transmitting a system clock signal, and a digital data transmission line for transmitting a digital data signal for exchanging time-divided digital data are provided. The master network clock is connected to the system clock transmission line and the digital data transmission line as an interface unit, and indicates the master network clock using an empty time slot of the digital data signal transmitted to the digital data transmission line. A specific master unit for generating a network clock signal and sending it to the digital data transmission line; and a system clock signal transmitted from the system clock transmission line, and the digital data signal transmitted via the digital data transmission line. Networks consisting of at least one general-purpose unit And a synchronization unit connected to the system clock transmission line and the digital data transmission line, receiving the network clock signal from the digital data transmission line, and synchronizing the system clock signal as a system clock signal based on the network clock signal. A DPLL that generates and sends a digital data signal to the system clock transmission line, and that transmits and receives a digital data signal via the digital data transmission line.
A digital network synchronization system including an L mounting unit is obtained.

Further, according to the present invention, in the above digital network synchronization system, the DPLL mounting unit designates an empty time slot in advance for a specific master unit, and the specific master unit transmits digital data. A frame synchronization signal indicating the start of a vacant time slot in the digital data signal transmitted to the service line is extracted to generate a vacant time slot mask signal corresponding to the position of the vacant time slot, and the vacant time slot mask signal and A network clock signal is transmitted to a digital data transmission line by adding a logical product signal obtained by performing a logical product with a network clock extracted from a digital network to a digital data signal in a designated empty time slot, and a DPLL is transmitted. Uses the AND clock signal as the reference Sampling at a predetermined position of the square wave indicated by the clock signal, and adjusting the period of the frame synchronization signal so that the rising position of the square wave of the network clock signal coincides with the predetermined position. Is obtained.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A digital network synchronization method and a digital network synchronization system to which the present invention is applied will be described in detail with reference to the drawings.

First, the outline of the digital network synchronization method of the present invention will be briefly described. This digital network synchronization method uses IS
For a digital data transmission, which is a transmission path of a digital data signal for exchanging time-divided digital data by a specific master unit among a plurality of network synchronization units connected and arranged as an interface unit by applying DN or the like. A network clock signal indicating a master network clock is generated using an empty time slot of the digital data signal transmitted to the line, and is transmitted to the digital data transmission line. A DPLL mounting unit and a plurality of network synchronization units connected to the system clock transmission line by receiving the signal, generating a synchronized system clock signal based on the network clock signal, and transmitting the generated system clock signal to the system clock transmission line. Synchronizes the network of the entire system.

According to such a digital network synchronization method,
In the conventional digital network synchronization method, a dedicated network clock transmission line required for synchronizing the network of the entire system is eliminated, and a specific master unit of the plurality of network synchronization units is connected to a digital data transmission line. Sends a network clock signal indicating a master network clock generated by itself using an empty time slot of the digital data signal transmitted to the digital data transmission line, and the DPLL mounting unit transmits a system clock signal synchronized with the network clock signal. Since it is only necessary to obtain the function of generating and transmitting the generated signal to the system clock transmission line, it is possible to rationally synchronize the network of the entire system with a small-scale configuration.

FIG. 1 is a block diagram showing a basic configuration of a digital key telephone system according to an embodiment of a digital network synchronization system to which the digital network synchronization of the present invention is applied.

This digital network synchronization system has a system clock transmission line S for transmitting a system clock signal.
1, a digital data transmission line S2 which is a digital data signal transmission path for exchanging time-divided digital data, and a system clock transmission line S1 and digital data transmission as an interface unit mutually by applying ISDN or the like. While being connected to the service line S2,
A specific master unit for generating a network clock signal indicating a master network clock using an empty time slot of a digital data signal transmitted to the digital data transmission line S2 and transmitting the generated network clock signal to the digital data transmission line S2, and a system clock system clock signal from the transmission line S1 is transmitted, a plurality of network synchronization unit 20 ₁ to 20 _n of at least one general-purpose unit for exchanging digital data signals and via a digital data transmission lines S2,
It is connected to the system clock transmission line S1 and the digital data transmission line S2, receives the network clock signal from the digital data transmission line S2, and generates a system clock signal synchronized based on the network clock signal. DPLL10 to be transmitted to system clock transmission line S1
DPLL mounting unit 1 for transmitting and receiving digital data signals via digital data transmission line S2
0.

[0016] That is, in this digital key telephone system, along with the network synchronization unit 20 _one of the plurality of network synchronization unit 20 ₁ to 20 _n is a particular master unit, network clock for transmission was conventionally required line and S3 is being eliminated, the digital data transmission by generating a network clock signal indicating a master network clock using the idle time slots of the digital data signal transmitted by the network synchronization unit 20 ₁ into digital data transmission line S2 The network clock signal from the digital data transmission line S2 is received by the DPLL 10a of the DPLL mounting unit 10, and a synchronized system clock signal is generated based on the network clock signal to generate a system clock signal. the system clock signal to each network synchronization unit 20 ₁ to 20 _n by outputting to line S1 Results to be sent, the network synchronization of the entire system by the system clock is connected to the transmission lines S1 the DPLL mounting unit 10 and the network synchronization unit 20 ₁ to 20 _n are adapted to be taken.

FIG. 2 shows a specific master unit (network synchronization unit 2) provided in the digital key telephone system.
0 ₁₎ is a timing chart illustrating the signal operation processing between the DPLL implementation unit 10.

Here, the DPLL mounting unit 10 is
The idle time slots contained in the digital data signal via a digital data transmission line S2 specified network synchronization unit 20 _1, the digital data signal the network synchronization unit 20 ₁ is transmitted to the digital data transmission line S2 as specified , A frame synchronization signal a indicating the start of an empty time slot is extracted, an empty time slot mask signal b corresponding to the position of the empty time slot is generated, and a network extracted from the empty time slot mask signal b and the digital network DN. AND with the clock (AN
The network clock signal is transmitted to the digital data transmission line S2 by adding the logical product signal obtained in D) to the digital data signal in the designated empty time slot.

Therefore, DP of DPLL mounting unit 10
In the LL 10a, the network clock signal based on the logical product signal transmitted via the digital data transmission line S2 is sampled at a predetermined position C at the rising edge of the rectangular wave indicated by the reference sampling signal e. Since the sampling data of the square wave is 1, the period of the frame synchronization signal a is adjusted so that the rising portion of the square wave is moved rightward as indicated by the arrow A. Is zero, the period of the frame synchronization signal a is adjusted so that the rising portion of the rectangular wave is moved leftward as shown by the arrow B, and as a result, the predetermined position C of the rectangular wave shown in the reference sampling signal e is obtained. Frame synchronization signal a so that the rise of the square wave of the network clock signal transmitted at
Period and generates a system clock signal on the adjusted sent to the system clock transmission line S1 in which the system clock signal by each network synchronization unit 20 ₁ to 20 _n
To synchronize the network of the entire system.

That is, in the case of this digital key telephone system, since the network clock transmission line S3 is eliminated as compared with the conventional system shown in FIG. it has, moreover a logical product signal of the network clock is the network synchronization unit 20 ₁ is a particular master unit and extracted directly from a digital network DN in network clock transmission line S3 as in the prior art without the use as a master network clock A network clock signal indicating the master network clock generated indirectly as one input for obtaining is transmitted to the digital data transmission line S2, and the DPLL 10a of the DPLL mounting unit 10 is synchronized based on the network clock signal. The system clock signal is generated and transmitted to the system clock transmission line S1, thereby providing the system clock signal. It connected to the transmission line S1 DPL
L mounting unit 10 and the network synchronization unit 20 ₁ to 20
_n can rationally synchronize the network of the entire system.

[0021]

As described above, according to the digital network synchronization method of the present invention, a specific master unit among a plurality of network synchronization units connected and arranged as an interface unit is connected to a digital data transmission line. A network clock signal indicating a master network clock is generated using an empty time slot of the transmitted digital data signal and transmitted to the digital data transmission line, and the DPLL mounting unit converts the network clock signal from the digital data transmission line into a network clock signal. By generating a system clock signal synchronized on the basis of the system clock signal and transmitting the system clock signal to the system clock transmission line, network synchronization of the entire system is achieved by the DPLL mounting unit and the plurality of network synchronization units connected to the system clock transmission line. In the past, it was necessary to synchronize the network of the entire system. The dedicated network clock transmission line is eliminated, and the network clock of the system clock signal transmitted to the system clock transmission line is not used directly as the master network clock but used only indirectly as in the past. Thus, network synchronization of the entire system can be reasonably achieved. Further, in the digital network synchronization system to which the digital network synchronization method is applied, since the line for transmitting the network clock is eliminated, the wiring connection is simplified and the configuration can be reduced in size.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of a digital key telephone system according to an embodiment of a digital network synchronization system to which a digital network synchronization method of the present invention is applied.

FIG. 2 is a timing chart illustrating a signal operation process between a specific master unit and a DPLL mounting unit among network synchronization units provided in the digital key telephone system shown in FIG. 1;

FIG. 3 is a block diagram showing a basic configuration of a digital key telephone system according to an example of a digital network synchronization system to which a conventional digital network synchronization method is applied.

[Explanation of symbols]

10, 10 'DPLL implementation units _{10a, 10a' DPLL 20 1 ~20} n, 30 1 ~30 n network synchronization units S1 system clock for transmitting line S2 digital data transmission line S3 network clock for transmitting line DN Digital Network

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference)

Claims (3)

[Claims] 1. A digital data transmission path for transmitting a digital data signal for exchanging time-divided digital data by a specific master unit of a plurality of network synchronization units connected and arranged as an interface unit to each other. A network clock signal indicating a master network clock is generated using an empty time slot of the digital data signal transmitted to the line, and is transmitted to the digital data transmission line, and a DPLL (Digital Phase Lock) is generated.
(Loop) The mounting unit receives the network clock signal from the digital data transmission line, generates a synchronized system clock signal based on the network clock signal, and sends the synchronized system clock signal to the system clock transmission line. A digital network synchronization method, wherein network synchronization of the entire system is performed by the DPLL mounting unit and the plurality of network synchronization units connected to a system clock transmission line. 2. A system clock transmission line for transmitting a system clock signal, a digital data transmission line which is a transmission path of a digital data signal for exchanging time-divided digital data, and a mutual interface unit. A network clock signal connected to the system clock transmission line and the digital data transmission line, and indicating a master network clock using an empty time slot of the digital data signal transmitted to the digital data transmission line And a specific master unit for generating and transmitting the digital data signal to the digital data transmission line, and the system clock signal is transmitted from the system clock transmission line, and the digital data signal is transmitted and received through the digital data transmission line. Network synchronization comprising at least one general purpose unit A unit connected to the system clock transmission line and the digital data transmission line, receiving the network clock signal from the digital data transmission line, and synchronizing as the system clock signal based on the network clock signal; A digital phase locked loop (DPLL) unit for generating and transmitting the digital data signal to the system clock transmission line and transmitting and receiving the digital data signal via the digital data transmission line. Synchronization system. 3. The digital network synchronization system according to claim 2, wherein the DPLL mounting unit designates the empty time slot in advance for the specific master unit, and the specific master unit includes A frame synchronization signal indicating the start of the empty time slot in the digital data signal transmitted to the digital data transmission line is extracted to generate an empty time slot mask signal corresponding to the position of the empty time slot, and By adding a logical product signal obtained by performing a logical product between the time slot mask signal and the network clock extracted from the digital network to the digital data signal of the designated empty time slot, A network clock signal is transmitted,
In the PLL, the network clock signal based on the logical product signal is sampled at a predetermined position of a rectangular wave indicated by a reference sampling signal so that the rising position of the rectangular wave of the network clock signal matches the predetermined position. A digital network synchronization system for generating the system clock signal after adjusting the period of the frame synchronization signal.