JP2001153979A - Clock device for electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a clock device for electronic apparatus, in which a time error can be reduced even when a broadcast with time data is not received for a long period. SOLUTION: When a control part 1 counts a clock, the time value of a time area 4 for display and that of a time area 6 exclusively used for the clock in a memory 3 are counted up simultaneously. When the time data are obtained from a broadcast reception part 5, only the time value of the time area 4 for display is calibrated to the value of the time data. The time value of the time area exclusively used for the clock is set to be the same as the time value of the time area for display (S5). The difference between the time value of the time area exclusively used for the clock after a prescrived time elapses (S6) and the time value of the time area for display is found. A clock error is calibrated (S7). On the basis of the clock error, a counting-up operation is corrected so that the clock error is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a clock device for electronic equipment, and more particularly to a clock device for electronic equipment having a time calibration function.

[0002]

2. Description of the Related Art At present, electronic devices such as televisions often have a built-in clock function. The clock function is often realized by counting up the clock of the microcomputer by a built-in control microcomputer. That is, the clock of the microcomputer or the built-in timer counter that uses the clock as a source is counted by software processing of the microcomputer to realize a clock function.

In this case, the software processing is simple and does not require any additional circuits other than the microcomputer, so that it is advantageous in terms of cost and practical. However, the accuracy of the clock (time) is determined by the accuracy of the clock itself. In most cases, a crystal oscillator is used as the clock of the microcomputer, but the oscillation accuracy is 20 to 100 pp.
m, and if the accuracy of the crystal oscillator is 50 ppm, the accuracy of the timepiece is also 50 ppm. By the way, with this accuracy, the error per day (24 hours) is 60
(Seconds) × 60 (minutes) × 24 (hours) × 0.00005 = 4.32 (seconds), which is an error of about 30 seconds for one week and about two minutes for one month.
Therefore, although the accuracy of the timepiece is quite poor, it can be easily realized and is useful as a timepiece used as a guide, and is therefore mounted on many electronic devices.

On the other hand, in recent years, the number of broadcasts in which additional information is inserted during the vertical blanking period of a television video signal has been increasing. Specifically, it is a teletext broadcast in Japan, a teletext overseas, and a closed caption. These are to realize new services by the information added on the signal during the vertical blanking period, but in the United States it is legally necessary to respond to closed captions. The technique of utilizing the additional data during the vertical blanking period is very common in many televisions. That is, at present, the function of taking in the additional data during the vertical blanking period from the broadcast signal and decoding the data can be realized simply and inexpensively. I have.

[0005] By the way, broadcasts transmitting the current time as the additional information are increasing. Teletext has current time information as transmission information (program contents). In the United States, the current time is sent by an additional information service known as XDS. It is to be noted that such information is not added in all broadcasts, and varies depending on a specific broadcast station or a program. However, it is certain that the number of broadcasts transmitting the current time is increasing year by year. Also, time information is transmitted in radio broadcasting such as FM multiplex broadcasting, and this may be used.

Accordingly, the current time of the time information (hereinafter, referred to as the current time)
A highly practical clock function can be realized using the time data. The time data is, of course, very accurate.However, since the broadcast with the time data is not always received, the clock count is normally made based on the microcomputer clock as described above. Do. Then, when a broadcast having time data is received, the time data is used to calibrate (correct) the count value of the clock at that time. By doing so, even if the clock gradually goes wrong due to an error in the microcomputer clock, it returns to the correct time when receiving a program with time data, and it becomes a highly practical clock function. Clock devices for electronic devices such as televisions by the method are increasing,
It is becoming general.

FIG. 3 is a block diagram showing a timepiece device of a conventional electronic device. In FIG. 3, a control unit 1 is constituted by a microcomputer or the like, operates based on a clock input from a clock generation unit 2, and has a memory 3 to control each unit in the electronic device, as is well known. . Further, the control unit 1 counts the clock, calculates the time, saves the time value in the display time area 4 of the memory 3, updates the value by continuing the count, and uses the updated value for the time display. ing. The broadcast wave having time data is supplied to the broadcast receiving unit 5 via the antenna. The broadcast receiving unit 5
The received signal is demodulated and supplied to a reproduction unit (not shown) in the electronic device to reproduce audio, video, and the like, and time data representing the current time is extracted and supplied to the control unit 1. When the time data comes, the control unit 1 calibrates the time value of the display time area 4 to the value of the time data.

[0008]

The clock is calibrated and accurate as long as the program having the time data is received, but the user does not always receive the program having the time data frequently. There is a problem. Until the time data is received, clock errors are accumulated. Program viewing varies greatly depending on the user's usage or the program composition of the broadcasting station.
It is quite possible that a program with time data will not be viewed for about a week. Also, it is often the case that the television is disconnected without using it for several days. Therefore, in this case, an error is generated that is not very practical for a timepiece, and when calculated with 50 ppm accuracy as described above, an error of about 30 seconds per week occurs.

There is a possibility that the time data cannot be obtained for a longer period of time. Although the time is more accurate than the clock using only the clock of the microcomputer, the time error becomes large unless a broadcast having the time data is received for a long time. There was a disadvantage of becoming. The present invention has been made to solve the above-described problem, and has as its object to provide a timepiece device of an electronic device that can reduce a time error without receiving a broadcast having time data for a long period of time.

[0010]

In order to achieve the above object, a clock generator for generating a clock, a memory having at least a display time area and a clock-dedicated time area, and time data representing a current time are provided. A broadcast receiving unit that receives a broadcast and extracts the time data, and counts the clock, thereby simultaneously counting up the time values of the display time area and the clock dedicated time area, and the broadcast receiving unit A control unit for calibrating only the time value of the display time area to the time data value when time data is obtained, wherein the control unit is dedicated to the clock. After setting the time value of the time area to be the same as the time value of the display time area, the clock dedicated time area after a predetermined time has elapsed. Calculating a clock error by calculating a difference between the time value of the display and the time value of the display time area, and correcting the count-up operation based on the clock error so as to reduce the clock error. A clock device for an electronic device, which is a feature of the invention, is provided.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the points of the present invention will be described. The problem of the conventional example is caused by the accuracy of the microcomputer clock, that is, an error. Therefore, if the value of the clock error can be calculated, the clock may be corrected by the error and counted in the clock counting process by the microcomputer. Since this process is software, it is very simple if only the value of the error is known. In the present invention, using the time data added to the broadcast, this value is compared with a time value obtained by counting the microcomputer clock, and an error value of the microcomputer clock is obtained from the difference. That is, since the time data is accurate, the difference is the error of the microcomputer clock itself.

FIG. 2 is a block diagram showing an embodiment of the present invention. 2, the same parts as those of the conventional example shown in FIG. 3 are denoted by the same reference numerals, and the description thereof will be omitted. Memory 3 is
It has a display time area 4 and a clock dedicated time area 6 along with a number of other areas. The control unit 1 normally counts clocks, and displays the display time area 4 of the memory 3.
In addition, the time values of the clock-dedicated time area 6 are simultaneously counted up by the same amount (that is, the time values of these two areas advance at regular intervals from the clock count).

The control unit 1 calibrates the time value of the display time area 4 to the value of the time data by using the time data supplied from the broadcast receiving unit 5 in the same manner as in the conventional example. The value of the area 6 is not corrected (corrected) during a predetermined time (for example, 10 hours). And
When a program having time information is received after a lapse of a predetermined time or more, a difference between the time values of the two areas is obtained and divided by the elapsed time, whereby an error in a time unit is obtained.

FIG. 1 is a flowchart for explaining the operation of the clock error calculation according to the present invention, which is mainly performed under the control of the control unit 1. When the program starts, first, it is determined whether or not the program received by the broadcast receiving unit 5 is a program having time data (S1: step 1). If it is not a program having time data (N), the process moves to the next process and returns to the start. If the program has time data (Y), it is determined whether FLAG is 1 (S2). At first, since FLAG is not 1 (N), the time value of the clock exclusive time area 6 is made the same as the time value of the display time area 4 (S3), and FLAG is set to 1
(S4), and then proceed to S5. If FLAG is 1 in S2 (Y), the process directly proceeds to S5.

Next, the time value in the display time area is calibrated to the value of the received time data (S5). Then, in S4, F
It is determined whether or not a predetermined time (for example, 10 hours) has elapsed since LAG was set to 1 (S6). If the predetermined time has not elapsed (N), the process proceeds to the next process and returns to the start. If the predetermined time has elapsed (Y), a clock error is calculated (S7), FLAG is set to 0 (S8), and the process proceeds to the next processing and returns to the start. Here, the clock error may be calculated by (time value of clock dedicated time area 6−time value of display time area 4) ÷ predetermined time.

Thereafter, in the timekeeping process of the timepiece, the error is corrected, a count-up operation is performed, and the time counter value is advanced. As a specific example, if the error is -50 ppm, -50 ppm means that it is delayed by 0.1 second every 33 minutes and 20 seconds. What is necessary is just to correct so that it may advance. This correction is continuously performed, and when the calculation of the clock error is completed, the next program having the time data is received, then the calculation of the next clock error starts, and the correction processing is always performed using the latest error value. Will be performed.

By this correction processing, accurate clock accuracy can always be ensured even when a program having time data is not received for a long period of time. Further, since the measurement of the error value is constantly performed and updated, the error can be corrected according to the aging and aging of the crystal oscillator, and the accuracy of the timepiece can be secured accurately.

[0018]

The clock device of the electronic apparatus according to the present invention has an extremely excellent effect that a time error can be reduced without receiving a broadcast having time data for a long period of time.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating an operation of calculating a clock error according to the present invention.

FIG. 2 is a block diagram showing an embodiment of the present invention.

FIG. 3 is a block diagram showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Control part 2 Clock generation part 3 Memory 4 Display time area 5 Broadcast receiving part 6 Clock exclusive time area

Claims (1)

[Claims] 1. A clock generator for generating a clock, a memory having at least a display time area and a clock-dedicated time area, and a broadcast receiving a broadcast having time data representing a current time and extracting the time data A receiving unit, by counting the clock, simultaneously counts up the time value of the display time area and the clock-dedicated time area, and when the time data is obtained from the broadcast receiving unit, the display time. And a control unit for calibrating only the time value of the area to the value of the time data, wherein the control unit converts the time value of the clock dedicated time area to the time of the display time area. Set it to the same value
A clock error is calculated by calculating a difference between a time value of the clock dedicated time area after a predetermined time or more and a time value of the display time area, and based on the clock error, the clock error is reduced. A timepiece device for an electronic device, wherein the time-up operation is corrected.