JP2020072363A - Serial communication circuit - Google Patents

Abstract

To provide a serial communication circuit that can detect deterioration of a serial communication circuit and can prompt replacement and repair before a device failure of a level that makes communication impossible occurs.SOLUTION: A serial communication circuit 100 that uses, as received data, a value determined to be majority by majority decision of sampled n pieces of received data includes a mode setting unit that switches between a normal communication mode and a life determination mode for detecting the waveform quality of serial communication, a sampling data determination unit that determines a point that is obtained by sampling data at the beginning of the data and the trailing end of the data and can be read correctly from among a plurality of sampling points after shifting to the life determination mode, and a life determination unit that compares the correctly read point with a reference value, and determines that the life of the serial communication circuit is near when there is a difference which is a threshold value or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a life detection method for a communication circuit that performs serial communication.

  There is a communication circuit such as UART (Universal Asynchronous Receiver Transmitter) as an integrated circuit for converting a serial signal by an asynchronous method into a parallel signal and for converting in the opposite direction. The communication circuit obtains received data by detecting a start bit included in communication data, generating a sampling clock, and sampling the communication data during a high level period of the sampling clock. There is also known a technique for determining the code of each 1 symbol by using a majority decision method from data taken in every 3 periods of 1 symbol (Patent Document 1).

  The timing of the sampling clock can be changed arbitrarily. For example, when the start timing of the sampling clock is shifted, if the leading data and other data are different among the multiple data captured for majority voting, the sampling clock timing is shifted to correct the data reading point. A technique for performing the above is known (Patent Document 2).

  On the other hand, the communication circuit is composed of ICs on the transmitting side and the receiving side, and components such as a damper resistor and a filter on the communication line. The characteristics of these parts may change due to factors such as overvoltage, high temperature, and deterioration over time. For example, the rise time and the fall time of the communication waveform may change due to the deterioration of the signal drive characteristics due to the failure of the communication IC and the change of the resistance value due to the failure of the damper resistance.

JP, 11-341089, A Japanese Patent No. 5896602

  If the waveform quality deteriorates due to the failure or deterioration of the parts, a data acquisition error is likely to occur. Further, if a deteriorated part is left unattended, it may deteriorate further and communication may become impossible. It is inconvenient for the user to suddenly lose communication and stop the operation of the device. There is a need for a method that can detect failure / deterioration of parts in advance, detect the degree of deterioration before communication suddenly stops, and prompt repair / replacement in advance.

In order to solve the above problems, the serial communication circuit according to the present invention,
In a serial communication circuit in which the value determined to be majority by the majority decision of the sampled n pieces of reception data is used as reception data,
It has a mode setting unit that switches between a normal communication mode and a life determination mode for detecting the waveform quality of serial communication,
After shifting to the life determination mode, a sampling data determination unit that determines the point at which the data can be correctly read by sampling the data at the beginning of the data and the trailing end of the data among a plurality of sampling points,
The present invention is characterized by including a life determining unit that compares correctly read points with a reference value and, if there is a difference equal to or greater than a threshold value, determines that the serial communication circuit has a short life.

  According to the serial communication circuit of the present invention, it is possible to detect the degree of deterioration of the serial communication circuit and prompt replacement and repair before a device failure of a level at which communication becomes impossible occurs.

Block diagram of serial communication circuit Illustration of sampling timing for serial communication Explanatory drawing of sampling timing setting in life judgment mode Image of communication waveform when communication circuit deteriorates Flowchart in Example 1 Explanatory drawing of sampling points in life judgment mode

  Hereinafter, modes for carrying out the present invention will be described with reference to the drawings.

  In the first embodiment, a method will be described in which the timing of data sampling is intentionally shifted, the degree of waveform blunting is detected, and it is determined whether or not deterioration is progressing.

<Block diagram of the present invention>
FIG. 1 shows a block diagram of the invention.

  The serial communication circuit 100 is an electric device including a circuit that performs serial communication internally, and internally includes a master-side communication circuit 200 and a slave-side communication circuit, and both perform serial communication.

  The master side communication circuit 200 is a circuit on the data transmission side in serial communication.

  The slave communication circuit 300 is a circuit on the data reception side in serial communication.

  The data transmission unit 201 of the master side communication circuit 200 performs serial conversion of the data to be transmitted and transmits the data to the slave side communication circuit 300. In the case of the life determination mode, predetermined data (for example, a data string that toggles 1, 0) is transmitted multiple times.

  The mode setting unit 101 determines whether the “normal mode” in which normal serial communication is performed or the “lifetime determination mode” in which deterioration of the serial communication circuit is detected, and transmits information to the communication control unit 202 and the data transmission unit 201. .. It should be noted that which mode should be selected may be determined by receiving a user's designation from a UI (User Interface) (not shown), or may be switched to the life determination mode after a certain period of time e.g. one month, Alternatively, a method of periodically changing the life determination mode after a specific operation may be used.

  The communication control unit 302 detects a start bit included in communication data and generates a sampling clock for sampling the communication data. The sampling clock has a frequency that is m (m is an integer of 4 or more) times the bit rate (frequency) of communication data, and is n pulses (n is an odd number smaller than m) that continues in one bit period of communication data. In the following description, for example, m = 8 and n = 3 will be described. That is, as shown in FIG. 2, the sampling points are selected from three consecutive points out of eight timings per one bit period of communication data. The sampling clock frequency and timing can be set to optimal values according to the data frequency and the waveform timing of the communication circuit. Further, in the life determination mode, the setting such as increasing the frequency of the sampling clock (for example, m = 16) may be changed in order to improve the detection accuracy. When the mode information received from the mode setting unit 307 is the normal mode, after the start bit is detected, sampling is performed at a sampling point set in advance according to a certain waveform of the communication circuit. In the case of the life detection mode, by setting the sampling point from the beginning of the eight sampling points or from the trailing end, sampling is performed on the side where the leading end and the trailing end of the data are located. Although a method of separately determining the front end and the rear end in the life detection mode will be described here, a method of simultaneously sampling (here, at eight points simultaneously) at all sampling points may be used.

  The reception data sampling unit 301 samples communication data using a 3-pulse sampling clock during the 1-bit period of the communication data. In the normal mode, the obtained received data is supplied to the majority decision unit 203. In the case of the life determination mode, when the data changes from HIGH to LOW for the sampling points set to the leading 3 points and the sampling points set to the trailing 3 points for the predetermined arbitrary data, It divides at the time of transition from LOW to HIGH, performs sampling a plurality of times, and transmits it to the sampling data determination unit 305.

  The majority decision circuit 303 makes a majority decision on the reception data sampled in the 1-bit period, and supplies the reception data having the value determined to be majority to the reception data storage section.

  The reception data storage unit 304 stores the reception data supplied from the majority decision unit 303, for example, for one frame, and supplies the stored reception data from the terminal 102 to the CPU in accordance with a read request from the CPU, which is a higher-level device (not shown). ..

  FIG. 3 is an explanatory diagram of sampling timing setting in the life determination mode.

  The sampling data determination unit 305 determines whether the reception data received from the reception data sampling unit 301 in the life determination mode is correctly read according to the data arbitrarily determined in the life determination mode. If the values of all three data are different from the transmission data at the first 3 points and the last 3 points of the sampling points, the communication control unit 302 is notified to shift the sampling points and perform sampling again. .. The above flow is repeated until the boundary between the point where the flow can be correctly read and the point where the flow is incorrect can be determined. As described above, when all the sampling points are viewed at the same time, the boundary between the correctly readable point and the erroneous point can be determined at once, and thus the repeated operation is unnecessary.

  The life determining unit 306 compares the information indicating which sampling point of the data received from the sampling data determining unit 305 has been correctly read with a reference value, and when a deviation of a threshold value or more occurs, it is the life of the communication circuit. To determine. The reference value may be a value in which the result of the initial state of the device is stored or the result of the previous determination in the life determination mode.

  The CPU (not shown) reads the determination result from the reception data terminal 103 as necessary, and notifies the user that the service life is near, for example, or the network unit (not shown) notifies the administrator of the device of the determination result. To encourage replacement. That is, when the life determining unit determines that the life is near, it notifies the user through an I / F such as a UI.

<Explanation of waveform at the end of life>
The communication waveform when determining the life will be described with reference to FIG. FIG. 4A is a waveform image before deterioration of the communication circuit. The solid line is an example of a real waveform. The slave-side communication circuit that has received the actual waveform performs binarization based on a threshold value (for example, HIGH level 2.1 V or higher and LOW level 0.7 V or lower) in view of the waveform voltage. The value at the timing of each sampling point is read from the binarized data. In FIG. 4A, the sampling point is set to the head side, and all points are correctly read.

  On the other hand, FIG. 4B is an image when the rising of the waveform becomes slower than that of FIG. 4A due to deterioration of components of the communication circuit. Since the rise time of the actual waveform is delayed, the timing of transition from LOW to HIGH during binarization is delayed, and as a result, the correct values (HIGH here) at the first two sampling points cannot be read. Here is an example. Although the example in which the rising time changes is shown here, the falling time may change. Therefore, the sampling data in the life determination mode is sampled at four types of points, a rising waveform and a falling waveform when the sampling point is at the beginning and a rising waveform and a falling waveform when the sampling point is at the trailing end.

<Flowchart>
The operation flow in the first embodiment will be described with reference to FIG. Since the operation in the normal mode is a known operation, a description thereof will be omitted. Here, the flow in the life determination mode will be described.

  In step S501, the mode setting unit 101 determines whether the operation mode is the normal mode or the life determination mode. Here, the fact that it is the life determination mode is transmitted to the communication control unit 302 and the data transmission unit 201.

  In step S502, if the communication control unit 302 is in the life determination mode, the communication control unit 302 sets the sampling points to the top three points.

  In step S503, the data transmission unit 201 transmits the determined arbitrary data (for example, data obtained by toggling 1, 0 or the like). The received data sampling unit 301 samples the received data at the positions of the first three points, and sends the result to the sampling data determination unit 305. The sampling data determination unit 305 determines whether or not the three sampling data points are correctly read.

  In step S504, the sampling data determination unit 305 determines whether all or part of the sampling data is correctly read. If all or part of the sampling data is correctly read, the process proceeds to S506. If all the sampling data are erroneously read, the process proceeds to S505.

  In S505, when all the sampling data are erroneously read, the sampling data determination unit 305 changes the setting of the sampling point to the center and re-sets because the boundary of the correct reading timing is located in the center of the sampling point. Communicate and sample.

  In step S506, the communication control unit 302 sets three sampling points on the trailing end side after the sampling on the leading end side is completed.

  In step S507, the data transmission unit 201 transmits the determined arbitrary data (for example, data obtained by toggling 1, 0, etc.). The reception data sampling unit 301 samples the received data at the positions of the three rear end points and transmits the result to the sampling data determination unit 305. The sampling data determination unit 305 determines whether or not the three sampling data points are correctly read.

  In step S508, the sampling data determination unit 305 determines whether all or part of the sampling data is correctly read. If all or part of the sampling data is correctly read, the process proceeds to S510. If all the sampling data are erroneously read, the process proceeds to S509.

  In S <b> 509, if all the sampling data are erroneously read, the sampling data determination unit 305 changes the setting of the sampling point to the middle, and again, because the boundary of the correct reading timing is located in the middle of the sampling point. Communicate and sample.

  In step S510, the life determination unit 306 compares the boundary between the points where the sampling data is correctly read with the reference. For comparison, as shown in FIG. 6, when the sampling point is set to 3 points on the leading side, the data changes from 1 to 0, and when the data is set to 3 points on the leading side, the data changes from 0 to 1. , When the data is set to 3 points on the trailing end side, the data changes from 0 to 1, and when the data is set to 3 points on the trailing end side, changes from 1 to 0. Each of the four patterns is judged. .. Further, in consideration of the variation, the results of whether or not the data were correctly sampled by sampling a plurality of times may be averaged. The determination result is compared with a reference value to determine the difference in the correct reading range. If the difference is equal to or larger than the threshold value, that is, if the correct reading range is narrower than the threshold value, the process proceeds to S512. If the difference is less than or equal to the threshold value, that is, if the correct reading range is not narrower than the threshold value, the process proceeds to S511.

  In step S511, the life determination unit 306 determines that the life is not near. The mode setting unit 101 sets the normal mode, transitions to the normal serial communication mode, and ends the process.

  In step S512, the life determination unit 306 determines that the life is near. Notify the user or administrator of the judgment result by some method. The mode setting unit 101 sets the normal mode, transitions to the normal serial communication mode, and ends the process.

  With the above processing, by changing the sampling point in the life determination mode of the serial communication circuit, it is possible to detect the deterioration of the waveform quality and determine whether the circuit has a short life.

100 serial communication circuit, 200 master side communication circuit, 201 data transmission unit,
300 Slave side communication circuit

Claims (8)

In a serial communication circuit in which the value determined to be majority by the majority decision of the sampled n pieces of reception data is used as reception data,
It has a mode setting unit that switches between a normal communication mode and a life determination mode for detecting the waveform quality of serial communication,
After shifting to the life determination mode, a sampling data determination unit that determines the point at which the data can be correctly read by sampling the data at the beginning of the data and the trailing end of the data among a plurality of sampling points,
A serial communication circuit comprising a life determining unit that compares correctly read points with a reference value and determines that the life of the serial communication circuit is near when there is a difference of a threshold value or more.   The serial communication circuit according to claim 1, wherein the frequency of the sampling point in the life determination mode is set to a frequency higher than the sampling frequency in the normal mode.   The sampling data determination unit is configured to change the high level of the data to the sampling of the rear end of the data when the high level of the data is changed to the low level and the low level is changed to the high level for the sampling of the head of the data. 2. The serial communication circuit according to claim 1, wherein a determination is made individually when changing from a low level to a low level and when changing from a low level to a high level.   The serial communication circuit according to claim 1, wherein when the life determining unit determines that the life is near, the user is notified via an I / F.   The serial communication circuit according to claim 1, wherein the reference value stores data before deterioration of the serial communication circuit and is read at the time of determination.   2. The serial communication circuit according to claim 1, wherein the reference value stores data obtained when the life is determined last time and is read at the time of the determination.   The serial communication circuit according to claim 1, wherein the mode setting unit performs a transition from the normal mode to the life determination mode each time a fixed period elapses.   The mode setting unit performs the transition from the normal mode to the life determination mode every time after performing a certain specific operation, or when the specific operation is performed a predetermined number of times or more. 1. The serial communication circuit according to 1.