1997-01-21
1998-08-04
Chung, Phung M.
Excavating
371 55, 371 201, G06F 1100
Patent
active
057905584
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a numerical control apparatus for communicating with external equipments by performing an error detection communication or an error correction communication, and more particularly to a numerical control apparatus for easily analyzing and eliminating a cause of the stoppage of the whole system due to a communication abnormality.
BACKGROUND ART
A numerical control apparatus for use in controlling a machining tool or the like transfers information by parallel or serial communications with various external units, such as a servo amplifier and an external I/O device, which are installed separately from the numerical control apparatus. In the parallel or serial communication, an information to be transferred is affected by an external noise penetrated into the communication line from outside to cause a communication failure depending on a magnitude and kind of the external noise. In order to improve the communication reliability and to transfer accurate information even in the presence of communication failures, the numerical control apparatus performs an error detection communication or an error correction communication so that normal communications are achieved. In the error detection communication, an error detection code such as a CRC code is added to data, and if an error is detected in the received data, a retransmission command is issued to receive the data again. In the error correction communication, an error correction code such as a hamming code is added to data, an error is not only detected in the received data but also corrected.
The number of communications may exceed an allowable retry number in the error detection communication or the error is not corrected in the error correction communication, depending on the magnitude of an external noise or the status in which the external noise is penetrated into the communication line. In such cases, it is inevitable to stop the system as the communication abnormality has occurred. In order to avoid the stoppage of the system, it is necessary to specify the communication line on which a communication failure has occurred, and to take a countermeasure, such as reducing of the noise penetrating into the communication line or the penetration rate of the noise, but it has been difficult even to consider the countermeasures.
DISCLOSURE OF INVENTION
It is an object of the present invention to make it easy to consider countermeasures for eliminating a cause of the stoppage of the system due to noise penetrated into a communication line, and also to make it possible to confirm effectiveness of the countermeasures.
According to a first aspect of the invention, a numerical control apparatus comprising: error detection communicating means for receiving data, to which an error detection code is added, through communication lines and for issuing a retransmission command to receive the data again when an error is detected in the received data; monitoring means for monitoring names of the communication lines on which the communicating means detects the error in the received data, the number of error detections and the time of the communication and for outputting the monitored information; error detection status storing means for observing and storing the information outputted from the monitoring means for each communication line and for outputting an error detection status for each communication line; and display means for displaying the error detection status outputted from the error detection status storing means for each communication line, in response to a command from an operator.
According to a second aspect of the invention, a numerical control apparatus comprising: error correction communicating means for receiving data, to which an error detection code is added, through communication lines and for correcting an error in the received data when the errors have been detected; monitoring means for monitoring names of the communication lines on which the error of the received data has been corrected, the number
REFERENCES:
patent: 4924496 (1990-05-01), Figa et al.
patent: 5297196 (1994-03-01), Yamada et al.
Chung Phung M.
Fanuc Ltd.
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