JPS6174433A - Two-wire bus connection system of terminal equipment and network terminator - Google Patents

Abstract

PURPOSE:To take easily frame synchronization of each terminal equipment by comparing the coincidence between a transmission monitor bit and a reception monitor bit at a terminal equipment so as to adjust a delay circuit. CONSTITUTION:The terminal equipment TE has a random pulse generator FG, a variable delay circuit D, and a phase detection circuit PD. Then plural equipments TE are connected to the network terminator NT via a bus BUS. Then the equipment TE transmits a phase adjusting monitor bit M at the head of frame, the equipment NT identifies the bit M by means of fixed sampling and the content of identification to the equipment TE as an m-bit. The equipment TE receiving it adjusts the circuit D so that the received content in m-bit is made coincident with the transmitted signal in M-bit. In adjusting the delay time in this way, the delay time difference from each equipment TE to the equipment NT is eliminated to take frame synchronization of each equipment TE at the same time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an interface configuration system between a plurality of terminal devices and a network termination device, and particularly to a two-wire passive bus connection system.

For example, in the digital integrated service network 15DN and the advanced information communication system INS, the interface between a plurality of terminal devices and a network termination device is particularly important. For this reason, an interface configuration using a 4-wire passive path is currently recommended for I5DN-oriented terminal devices, and implementation is being promoted.

There is a strong demand for this service to be provided.

[Conventional technology]

Generally, when a bus connection is used, several information channels must be transmitted to the bus line in a time division multiplexing manner, so phase synchronization of each (ff) information channel is required.

Furthermore, when using a two-wire path connection, the button requires technology for multiplexing and bidirectional transmission.

The bus configuration differs depending on the arrangement of each terminal and network termination device and the connection distance, and the transmission delay time for each terminal is KA, so a special interphase ILI is used for multiplexing and bidirectional transmission.
I need some help.

Therefore, a two-wire interface is used to communicate with multiple terminal devices.
T! One of the conventional examples with the net end 4 of L (U connected) is the 5th one.
The explanation will be given according to the block connection diagram shown in the figure.

The figure shows a two-wire multiple terminal bus connection system, in which a plurality of terminals 3A and 3A (hereinafter referred to as Tg) are connected via a 2-wire path transmission line BUS to a terminal device NT (Y lower network). (Terminal device is called NT) Hold VCC.

In this conventional example, an active terminator AT' (hereinafter referred to as AT) is provided at one end of the two-wire bus +3 US.

In this connection method, each terminal t from TFJ
The multiplexing operation of the H-report channel is performed as follows.ζAT
receives the frame sent from the NT, establishes 7-frame synchronization, and sends only a synchronization signal to the NT using the synchronization phase.

Then each TE following the bus transmission path! Toward iNT
In order to multiplex and transmit the end information channels, the above N
It synchronizes with the synchronization signal for T and sends a signal to each information channel in the frame for NT.

Also, the transmission of the R channel from NT to TE is
This is done by synchronizing E with the black frame imported from NT, and manually controlling the information channels of each terminal device within that frame.

[Problem that the invention seeks to solve]

An active terminator AT is indispensable at the tip of the bus for the two-wire multi-terminal bus connection system described above. AT now for some reason
If a failure occurs in the NT, all of the intermediary TEs may become unsynchronized. ATK requires high reliability, and the AT needs to be supplied with power from the NT without interruption during cutting in this method. There is also a problem.

Furthermore, in order to synchronize frames going from VcAT to NT, K is the location of NT and the length of the bus branch line to each TE. The monitor bit M is transmitted from each terminal device equipped with a signal delay means to the network #! as the first bit of the frame. The network terminal device receives and identifies the monitor bit M using fixed sampling, and sends the identification content back to the terminal device using the monitor bit m, and the terminal device checks whether the transmitted monitor bit M and the received monitor bit m match. This problem is solved by a two-wire path connection system between a terminal device and a network terminating device according to the present invention, in which the delay means are adjusted by comparison.

[For production]

According to the present invention, the 2-wire path is a passive bus without using an active terminator! - The problem of power supply and reliability is improved.

In the present invention, a monitor bit is used to determine the signal delay W of each terminal device,
By making adjustments, it is possible to match the times of frames arriving at the network termination device from terminal devices located at different distances, and it is possible to multiplex each information channel sent from each terminal device to the network termination device.

Since a part of the required transmission/reception frame interval time following the last bit of the claim can be used as delay guard time (time used for delay adjustment), an increase in bit rate can be suppressed.

〔Example〕

The gist of the present invention will be explained in detail according to illustrated embodiments.

FIG. 1 is a block diagram of a bus connection system in which a plurality of terminal devices and a network termination device are connected to a two-wire passive bus IC.

Further, FIG. 2 shows an example of a frame structure for bidirectional burst mode transmission.

In FIG. 1, TE is a terminal device, NT is a network termination device, and BUS is a two-wire passive bus.

The terminal device TE has a random pulse generator FG, a variable delay circuit D1, and a phase detection circuit PD.

As shown in FIG. 2, the terminal equipment TE sends the phase adjustment monitor bit M at the beginning of the frame, and the network termination equipment flNT identifies the monitor bit M by fixed sampling and sets it as m bits'1: The identification content is sent to the terminal equipment. Return to TE.

In the terminal device TE, the variable delay circuit is adjusted to 5 so that the contents of the received m bits match the contents of the transmitted M bits. By adjusting the delay time by y4, the propagation time difference from each terminal device tTE is eliminated, and frame synchronization can be achieved at the same time.

In the embodiment shown in FIG. 1, the terminal equipment RNT can have two types. In Fig. 2, M is a monitor bit sent from the terminal equipment WTE, F is a frame bit, L is a DC balance bit, Bl'i is the channel information of each terminal, m, and frame bits are not required in the frame directed from the upper terminal device to the network terminating device, which is returned from the network terminating device.

The delay adjustment using the monitor bit M will now be explained with reference to the transmission/reception frame configuration diagram shown in FIG.

In the figure, the three rows of frames on the left side represent frames sent from the network terminal equipment and received by each terminal equipment. That is, at the nearest terminal, each terminal device starts transmitting the frame bit FId to the network terminal device after the guard time Tg for switching transmission and reception of bidirectional communication has elapsed.

However, up to this point, the frames received by the network terminating device do not have the same phase because the delay time differs depending on the distance from the terminal device.

Therefore, the monitor bit M according to the present invention is used to adjust the delay adjustment circuit of each terminal device, so that when the frame arrives at the network termination device, the frame from the nearest terminal device and the frame from the farthest terminal device are in the same phase. K so that it becomes.

In the figure, the top row on the right side shows frames that have arrived at the network terminal device, and the second row shows frames sent from the nearest terminal device. In the second stage, the delay amount of the delay adjustment circuit of the nearest terminal device is increased, that is, the phase of the monitor bit M is shifted to the right, so that the phase of the frame upon arrival at the network terminal equipment is as shown in the first stage shown in the figure. Adjust so that

The frame in the third row is for the farthest terminal device, and shows that the adjustment of the delay adjustment circuit starts from delay t'7r and ends with the delay adjustment amount being zero.

Generally, delay guard time TD (i.e., adjustable time @) is required for delay adjustment of monitor bit M.
If you set the delay adjustment to start from zero, the guard time TD will be Tg+T from the last bit of the monitor bit M of the transmission frame of the same device.

time interval.

Let's compare this with the case where the monitor bit is provided in the middle of the frame.

Diagram M4 shows the frame structure when there is another bit X before the monitor bit.

In Figure 3, the same parts as in Figure 3 are indicated using No. 7.

The frame received by the network termination equipment NT is shown at the top right. As is clear from the figure, between the last bit of the transmitted frame and the first bit of the received 7 frames,
It is possible to switch between sending and receiving communications. In addition, an additional guard time TD of 17A-jA is required during 71 frames. In this case, TD=2Tp.However, according to the present invention, the monitor bits are blanked, so that an increase in the overall bit rate can be suppressed.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to realize a two-wire path connection method that has a high degree of conspicuousness in the bus form and wiring form, that is, the length of the bus, and the HR relationship between the terminal device and the network termination device. The effect is great because it makes it easy for the monitor bit to participate in the frame, and by selecting the monitor bit at the beginning of the frame, a universal two-wire path connection with a good pit rate can be obtained.

[Brief explanation of the drawing]

Figure 81 is a block diagram showing an embodiment of the connection method of the present invention, Figure 2 is an example of the transmission and reception frame configuration, Figures 3 and 4 are transmission and reception frame diagrams, and Figure 5 is a diagram showing the conventional connection system. FIG. In the figure, TE is a terminal device, NT is a network termination device, BUS is a comparison circuit,
M+m is a monitor bit, F is a 7 frame bit, Tp is a propagation time, Tg is a transmission/reception switching guard time, and TD is a delay guard time.

Claims (1)

[Claims] A plurality of terminal devices and a network termination device are connected to a two-wire bus, and a monitor bit M is sent from each terminal device equipped with a signal delay adjustment means to the network termination device as the first bit of a frame,
The network terminal equipment receives and identifies the monitor bit M with fixed sampling, and sends the identification content back to the terminal equipment using the monitor bit m, and the terminal equipment adjusts the delay means by comparing the transmission monitor bit M and the reception monitor bit m. A two-wire bus connection system between a terminal device and a network termination device, characterized in that: