JPH0475695B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a communication system in which a main device and a slave device are connected facing each other via two pairs of transmission paths, or a communication system in which a main device and a slave device are connected in a multi-drop type. Concerning clock supply system.

A communication system in which a main device and a slave device are connected via two pairs of transmission paths is used as a local or in-house communication system.
There is a system described in "Method for realizing ISDN bus type user/network interface". In such systems, each slave device must extract and synchronize its clock from the received signal. However, in order to simplify the transmission line interface circuit of the slave device, it is better to make the clock supply from the main device to the slave device as simple as possible.

An object of the present invention is to supply a clock to slave devices with a simple circuit configuration.

According to the present invention, in the main device, a clock supply circuit is connected between intermediate taps of the transmission line side windings of two transformers connected to two transmission lines,
As for the slave device, a bus network clock supply system is obtained in which a clock receiving circuit is connected between the intermediate taps of the transmission line side windings of the two transformers connected to the two transmission lines.

Next, the present invention will be explained in detail with reference to the drawings. FIG. 1 shows the configuration of a communication system in which a main device and a slave device are connected in a multi-drop configuration. The communication system in Fig. 1 includes a main device 3, slave devices 4, 5,
6 are connected by buses 1 and 2, and the buses 1 and 2 are terminated at a termination device 7. FIG. 2 shows an embodiment of the present invention. In Figure 2, the main device 3
consists of transformers 31 and 32 connected to buses 1 and 2, a clock supply circuit 33, a transmitter circuit 34, and a receiver circuit 35, which are connected to the intermediate taps of the bus side windings of both transformers.
The circuit comprises transformers 51 and 52 connected to buses 1 and 2, a clock receiving circuit 53, a transmitting circuit 55, and a receiving circuit 54 connected to the intermediate taps of the bus side windings of both transformers. The slave devices 4 and 6 also have the same configuration as the slave device 5. In this embodiment, the main device 3 supplies a clock synchronized with the digital signal sent to the bus 1 to the slave devices 4, 5, and 6 from the clock supply circuit 33. This clock is provided through the intermediate tap of transformers 31 and 32, so it does not affect the digital signals on buses 1 and 2. Slave device 5 is connected to bus 1
The above digital signal is received via the transformer 51, and the clock from the main device 3 is also received in the clock receiving circuit 53. Based on this reception clock, the slave device 5 receives the digital signal on the bus 1 and also sends a transformer 52 to the bus 2.
The digital signal to be sent is sent out via the Since the clock receiving circuit 53 is connected to the intermediate tap of the transformers 51 and 52, no received signal or transmitted signal is superimposed on the received clock. FIG. 3 shows the termination device 7 used in this embodiment. The termination device 7 has transformers 71 and 72 connected to the buses 1 and 2, and the buses 1 and 2 are terminated by resistors 74 and 75, respectively. On the other hand, the clock signal is terminated by a termination circuit 73 connected to the intermediate tap of the bus side windings of transformers 71 and 72.

FIG. 4 shows a common configuration example of the clock supply circuit 33, the clock reception circuit 53, and the termination circuit 73. The circuit 83 is a circuit corresponding to these circuits, and is composed of a transformer 84 and a circuit 85. The circuit 85 is an oscillator in the clock supply circuit 33, a reception gate in the clock reception circuit 53, and a termination resistor in the termination circuit 73. Note that transformers 81 and 82 are transformers connected to buses 1 and 2, and correspond to transformers 31 and 32 in clock supply circuit 33, for example.

Another example of the circuit 83 is shown in FIG. In FIG. 5, circuit 85 is connected via capacitors 86 and 87 to intermediate taps of the bus side windings of transformers 81 and 82.

Although the above explanation has been based on the configuration shown in FIG. 1, the present invention also applies to a two-way communication system of a main device 3 and one slave device 4 as shown in FIG.
As shown in FIG. 2, a terminating device 9 having the same configuration as the terminating device 7 may be added, and the main device 9 may be connected in parallel to the buses 1 and 2.

In this way, the present invention eliminates the need for a clock extraction circuit and a synchronization protection circuit with complicated configurations in the slave device, and also reduces the synchronization establishment time to 0 when starting communication.
The transmission line interface circuit in the slave device can be simplified and the synchronization characteristics can be improved.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a communication system using the present invention. FIG. 2 is a block diagram showing an embodiment of the present invention, FIG. 3 is a diagram showing a termination device used in the present invention, and FIGS. 4 and 5 are diagrams showing a clock supply circuit and a clock receiving circuit used in the present invention. FIGS. 6a and 6b are block diagrams showing the circuit and termination circuit in common, respectively, showing the configuration of another communication system using the present invention. In the figure, 1 and 2 are buses, 3 is the main device, 4,
5 and 6 are slave devices, 7 is a terminal device, 31, 32, 5
1 and 52 are transformers, 33 is a clock supply circuit,
53 is a clock receiving circuit, 34 and 55 are transmitting circuits, and 35 and 54 are receiving circuits, respectively.

Claims (1)

[Claims] 1 In a bus network in which a main device and one or more slave devices are connected to two transmission lines via a transformer, the main device is
A clock supply circuit is connected between the intermediate taps of the transmission line side windings of two transformers connected to one transmission line, and in the case of a slave device, the clock supply circuit is connected to the transmission line side of two transformers connected to the two transmission lines. A bus network clock supply system characterized by connecting a clock receiving circuit between intermediate taps of a winding.