JPH04326830A - Transmission line selecting system - Google Patents

Abstract

PURPOSE:To switch a transmission line before a fault when there is any trouble in the accuracy of a clock frequency on the transmission line at a circuit to generate a clock synchronizing the phase to that of a clock extracted from the transmission line. CONSTITUTION:A synchronizing clock (b) is generated from a phase-locked clock oscillation circuit 2 to input a clock (a) extracted from the transmission line. The frequency of this synchronized clock is measured by a high-speed and high-accuracy clock. According to this measured result, the accuracy of the clock on the transmission line is judged, and the transmission line is switched. Thus, the fault caused by the abnormality of the clock accuracy on the transmission line can be prevented in advance.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission path selection method for a phase-locked oscillator circuit that oscillates a clock signal phase-synchronized with a clock signal extracted from a transmission path.

0002

[Prior Art] Conventionally, in the transmission path selection method, the accuracy of the clock frequency on the transmission path is not questioned, and the transmission path is continued until the clock signal itself is interrupted or a state in which phase synchronization is not possible in the phase synchronized oscillator circuit occurs. There was no switching.

0003

[Problems to be Solved by the Invention] In the conventional transmission path selection method described above, if the cause of a malfunction in the device to which the phase synchronized oscillation circuit supplies clocks is due to the clock frequency accuracy on the transmission path, monitoring is required to identify this problem. I didn't have the means.

[0004] An object of the present invention is to provide a transmission path selection system that solves these problems.

[0005]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the transmission line selection method of the present invention provides a phase-synchronized clock oscillator circuit that outputs a clock that is phase-synchronized with a clock signal extracted from a transmission line. A means for measuring the frequency of a synchronized clock generated by a phase synchronized clock oscillator circuit using a high-speed and high-precision clock signal, and a means for determining the clock accuracy of a transmission line from the frequency measurement result and controlling transmission line switching. have

The transmission path selection method of the present invention also includes a transmission path selector that selects and switches between a plurality of transmission paths and extracts a clock signal, and a clock signal that is extracted from the transmission path selected by the transmission path selector. a phase-synchronized clock oscillator that outputs a phase-synchronized clock; a frequency measuring device that measures the frequency of the synchronized clock generated by the phase-synchronized clock oscillator using a high-speed and high-precision clock signal;
The present invention is characterized by comprising an arithmetic processing unit that determines the clock accuracy of the transmission line from the frequency measurement result and controls the transmission line switching for the transmission line selector.

[0007]

Embodiments Examples of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention. This transmission path selection system includes a transmission path selector 1, a phase-locked clock oscillator (PLO) 2, a high-speed clock oscillator 3, a frequency measuring device 4, and an arithmetic processing unit 5.

The transmission path selector 1 selects a plurality of transmission paths (1 to 1).
Select one transmission line from n) and extract the clock signal.

The phase synchronized clock oscillator 2 outputs a clock that is phase synchronized with the clock signal extracted from the transmission path selected by the transmission path selector 1.

[0011] The high-speed clock oscillator 3 generates a high-speed and highly accurate clock and outputs it to the frequency measuring device 4.

The frequency measuring device 4 measures the frequency of the clock oscillator generated by the phase synchronized clock oscillator 2 using a high-speed and highly accurate clock.

The arithmetic processing unit 5 determines the clock accuracy of the transmission line based on the frequency measurement result and controls the transmission line selector 1 to switch the transmission line.

Next, the operation of this embodiment will be explained.

The synchronized clock signal b output from the phase synchronized clock oscillator 2 which receives the extracted clock signal a extracted from the transmission path via the transmission path selector 1 is outputted to other circuits, and is also used for frequency measurement. The signal is input to device 4. As shown in FIG. 2, the frequency measuring device 4 measures the output clock (high-speed clock) of the high-speed clock oscillator 3 within a period in which the output clock (synchronous clock signal) b of the phase synchronized clock oscillator is counted by a certain number of clocks. Count how many are included and measure the frequency based on this count. Frequency measurement is performed periodically and the measurement results are output to the arithmetic processing unit 5. When the input frequency measurement result exceeds a set threshold value, the arithmetic processing unit 5 controls the transmission path selector 1 to switch the transmission path for obtaining the extracted clock signal a.

[0016]

As explained above, the present invention can detect an abnormality in the clock accuracy of a transmission line by measuring the oscillation frequency of the output of a phase synchronized clock oscillator, and uses the measurement results to obtain an extracted clock. By switching the transmission path, it is possible to switch the transmission path before a failure occurs in another device.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing the operation timing of the transmission path selection method in FIG. 1;

[Explanation of symbols]

1 Transmission path selector 2 Phase synchronized clock oscillator 3 High-speed clock oscillator 4 Frequency measuring device 5 Arithmetic processing unit

Claims (2)

[Claims] Claim 1: In a phase-synchronized clock oscillation circuit that outputs a clock that is phase-synchronized with a clock signal extracted from a transmission path, the synchronized clock generated by the phase-synchronized clock oscillation circuit is frequency-controlled using a high-speed and highly accurate clock signal. 1. A transmission path selection method comprising: a means for measuring the frequency; and a means for determining the clock accuracy of the transmission path based on the frequency measurement result and controlling transmission path switching. 2. A transmission path selector that selects and switches between a plurality of transmission paths and extracts a clock signal, and a phase that outputs a clock whose phase is synchronized with the clock signal extracted from the transmission path selected by the transmission path selector. a synchronous clock oscillator; a frequency measuring device that measures the frequency of the synchronous clock generated by the phase synchronous clock oscillator using a high-speed and high-precision clock signal; 1. A transmission path selection method, comprising: an arithmetic processing unit that performs transmission path switching control on a selector.