JP2551666B2 - Clock supply switching circuit - Google Patents

Description

The present invention relates to a supply switching circuit for a clock used in a synchronous communication system and used for signal synchronization.

[Prior Art] Conventionally, in this type of clock supply switching circuit, when an external control circuit fails, switching is manually performed until the failure is recovered. For example, FIG. 2 is a diagram showing an example thereof. In the figure, 6A and 7A are clock supply circuits, respectively, which are adapted to input the input clocks 100 and 101 and output the output clock 102 from the clock supply circuit 6A.

The clock supply circuit 6A includes a disconnection detector 1 that detects a clock disconnection, and a selector 4 that switches the input clocks 100 and 101. Further, the clock supply circuit 7A has substantially the same configuration. And both clock supply circuits 6A, 7
A is connected to the external control circuit 8A, and the selector 4 is switched by the external switching signal 54 from the external control circuit 8A to switch the input clocks 100 and 101.

When the external control circuit 8A fails, the selector 4 or the like is manually switched to switch the clock.

[Problems to be Solved by the Invention]

In the above-described conventional clock supply switching circuit, when the external control circuit fails, it has to be manually switched, so the response to the failure is poor, during which the output of the synchronous clock is stopped and communication is cut off. Alternatively, there is a problem such as malfunction.

An object of the present invention is to provide a clock supply switching circuit capable of automatically switching the clock supply even if the external control circuit fails.

[Means for solving the problem]

The clock supply switching circuit of the present invention comprises a pair of clock supply circuits to which an input clock is input, and an external control circuit connected between these clock supply circuits. It has an internal control circuit that detects disconnection and outputs an internal switching signal.

Further, the external control circuit is configured to output an external switching signal based on the disconnection detection signal from the internal control circuit and also output a device alarm signal when the device itself fails.

Further, in the clock supply circuit, the internal switching signal output from the internal control circuit and the external switching signal from the external control circuit are switched and selected from the external switching signal when the device alarm signal is input. It has a selector and a selector that selects one of the input clocks by a switching signal output from the selector.

Here, the internal control circuit includes a disconnection detector that detects a disconnection of an input clock and a selector that selects a detection signal of a clock disconnection detected by itself or the other clock supply circuit and outputs an internal switching signal. are doing.

[Action]

In this configuration, when the external control circuit fails, the external switching signal is switched to the internal switching signal by the device alarm signal output from the external control circuit to switch the input clock.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram of one embodiment of the present invention. The clock supply circuit 6 has an internal control circuit 5 composed of a disconnection detector 1 and a selector 2, and further has a selector 3 and a selector 4. The internal control circuit 5 performs disconnection detection on the input clock 100 and outputs a disconnection detection signal 51. Further, the clock supply circuit 7 forming a pair with the clock supply circuit 6 has substantially the same configuration, and the internal control circuit of the clock supply circuit 7 performs disconnection detection on the input clock 101 and outputs a disconnection detection signal 52. To do.

The selector 2 of the internal control circuit 5 of the clock supply circuit 6 outputs the internal switching signal 53 when either one of the disconnection detection signals 51 and 52 is input, and outputs the internal switching signal 53 to one input terminal of the selector 3. Is being supplied to.

An external control circuit 8 is connected between the clock supply circuits 6 and 7. The external control circuit 8 can receive the disconnection detection signals 51 and 52 and output an external switching signal 54,
This is supplied to the other input terminal of the selector 3.
Further, the external control circuit 8 can output a device alarm signal 55 when it fails, and this is added to the control terminal of the selector 3.

Further, the input selectors 100 and 101 are input to the selector 4 of the clock supply circuit 6, and the switching signal 56 output from the selector 3 is added to the control terminals thereof.

According to this configuration, when the disconnection detector 1 of the clock supply circuit 6 does not detect a clock disconnection, the input clock 100 is output as the output clock 102 through the selector 4. When the disconnection detector 1 detects a clock disconnection, the selector 2 uses the disconnection detection signal 51 to switch the internal switching signal 53.
Is output to the selector 3. However, if the external control circuit 8 is normal at this time, the external switching signal 54 from this external control circuit 8 is selected by the selector 3 and output to the selector 4 as the switching signal 56, where the output clock 102 is the input clock. Switch to 101.

Furthermore, when the external control circuit 8 fails, a device alarm signal 55 is output from the external control circuit 8. As a result, the selector 3 selects the internal switching signal 53 and outputs it as the switching signal 56. As a result, in the selector 4,
This switching signal 56 enables input clock 100 and input clock 1
01 is switched and the output clock 102 is output.

〔The invention's effect〕

As described above, the present invention controls the selector that selects the input clock according to the device alarm output from the external control circuit, so that when the external control circuit is normal, the clock is switched by the external switching signal from the external control circuit. When the external control circuit fails or is maintained, the clock can be switched by the internal switching signal generated by the clock supply circuit, and a normal clock can always be automatically supplied. It also has an effect of preventing malfunctions.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional example. 1 ... Disconnection detector, 2-4 ... Selector, 5 ... Internal control circuit, 6,7,6A, 7A ... Clock supply circuit, 8,8A ... External control circuit, 51, 52 ... Disconnection detection Signal, 53 …… Internal switching signal, 54 …… External switching signal, 55 …… Device alarm signal, 56
...... Switching signal, 100,101 …… Input clock, 102 …… Output clock.

Claims (3)

(57) [Claims] 1. A pair of clock supply circuits to which an input clock is respectively input, and an external control circuit connected between these clock supply circuits, wherein the clock supply circuit internally detects disconnection of the input clock. An internal control circuit that outputs a switching signal is provided, and the external control circuit outputs an external switching signal based on a disconnection detection signal from the internal control circuit, and also outputs a device alarm signal when itself fails. The clock supply circuit further includes an internal switching signal output from the internal control circuit and an external switching signal from the external control circuit from the external switching signal when the device alarm signal is input. It has a selector for switching and selecting to a switching signal and a selector for selecting one of the input clocks by a switching signal output from this selector. Clock supply switching circuit, characterized in that. 2. An internal control circuit includes a disconnection detector for detecting a disconnection of an input clock, and a selector for selecting a clock disconnection detection signal detected by itself or the other clock supply circuit and outputting an internal switching signal. The clock supply switching circuit according to claim 1, which is configured. 3. The clock supply circuit according to claim 2, wherein each clock supply circuit outputs a clock disconnection detection signal from its own disconnection detector to an internal control circuit of the other clock supply circuit together with an external control circuit. Clock supply switching circuit.