Communication device possessing trouble detection function

Abstract

A clock supply select circuit controls supply of receive clock and transmit clock to a receiver and a transmitter. The clock supply select circuit includes a clock generate circuit generating internal clock of the reference, and clock modulate circuit generating a modulate clock signal modulated such that at least one of frequency fluctuation, phase fluctuation, waveform fluctuation and jitter is applied to the internal clock. In a normal operation mode, the internal clock is supplied as receive clock and transmit clock, and in a loopback operation mode, while the internal clock is supplied as receive clock, modulate clock signal is supplied as transmit clock.

Description

technical field [0001] The present invention relates to communication devices, and more particularly, to fault detection testing of communication devices. Background technique [0002] In various high-speed communication standards in recent years, the vibration component of the transmitted data has also increased along with the high transmission rate. In order to cope with such high-speed and high-vibration data, the operation of circuits for synchronizing external data with internal clocks, such as CDR (Clock Data Recovery: Clock Data Recovery) circuits and elastic buffers (Elasticity Buffer) in communication equipment The speed is also increased, and its configuration becomes complicated. [0003] For example, in USB2.0 (Universal Serial Bus Specification Revision 2.0), the latest serial interface communication standard that connects PCs (Personal Computer: Personal Computer) and peripheral devices, a high speed of 480MBPS (Mega-Bits PerSecond) is stipulated. serial comm...

AI Technical Summary

Problems solved by technology

[0006] However, in a conventional communication device in which the transmitter and receiver operate on the same clock, the loopback operation is close to the actual USB communication in which there are frequency errors, transmission vibrations, phase fluctuations, and waveform fluctuations of the clock signal (duty ratio, etc.). It is not possible to conduct abnormal verification tests of communication devices under the operating conditions

In particular, for the clock data recovery circuit and elastic buffer circuit that absorb these frequency errors, transmit vibrations, waveform fluctuations, and phase fluctuations, and synchronize external data with the internal clock, anomaly detection is practically impossible in conventional loopback operations

[0007] Therefore, since the test must be performed using an expensive and high-speed test device that can apply USB data to which frequency errors, transmission vibrations, waveform fluctuations, and phase fluctuations are added, there is a problem that the manufacturing cost of the communication device becomes high.

[0008] In addition, conventional communication devices do not have a device for quantitatively measuring the vibration component of USB communication data, so it is difficult to detect whether the waveform quality (vibration component) of the transmitter is within the specification by loopback operation

Therefore, it is necessary to use expensive high-speed test equipment to verify the abnormality detection of whether the waveform quality of the transmitter is within the specification, which also leads to an increase in the test cost and the increase in the manufacturing cost of the communication device.

[0009] Moreover, in the traditional communication device, it is necessary to lead the multi-bit low-speed receiving data and sending data to the outside of the communication device during the loopback operation.

Therefore, it is necessary to provide a plurality of signal input and output paths, which also leads to an increase in the cost of the communication device from this point of view.

[0010] In addition, traditional communication devices are dedicated to half-duplex communication in which the output of the transmitter and the input of the receiver are directly connected. When abnormal detection involving multiple communication devices is involved, half-duplex communication must also be used for abnormal detection, which is different from using full-duplex communication. Compared with the case where the duplex detection is abnormal, the time for the abnormality detection test is longer, and from this point of view, there is also a problem that the manufacturing cost of the communication device increases.

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