Patent Application
20130003506
The present invention relates to a radio-controlled watch that adjusts the time based on a signal received from a satellite.
There is known a radio-controlled watch that adjusts the time by receiving radio signal containing time information from an external time information supply source. As one type of such a radio-controlled watch, a study has been made on a radio-controlled watch that adjusts the time with the use of a signal received from a satellite, such as a Global Positioning System (GPS) satellite (see, for example, Patent Literatures 1 and 2).
In the above-mentioned radio-controlled watch, leap second correction is sometimes necessary in order to obtain the time under Coordinated Universal Time (UTC) from time information contained in a received signal. In the case where the signal transmitted by the satellite contains such information on the leap second, it is conceivable that the radio-controlled watch receives the information on the leap second to adjust the time information. However, in the case of a GPS satellite, for example, the information on the leap second is not transmitted as frequently as the time information, and hence the state of being unable to receive the information on the leap second may continue. Alternatively, it is also conceivable that the function for receiving the leap second information separately from the time information cannot be installed in the first place because of hardware restrictions or the like.
The present invention has been made in view of the above-mentioned problem, and therefore it is one object of the present invention to provide a radio-controlled watch capable of performing leap second correction even when information on the leap second is not received from a satellite.
According to the present invention, there is provided a radio-controlled watch that adjusts time by receiving a signal containing time information from a satellite, the radio-controlled watch including: storage means for storing a leap second correction value to be used for leap second correction with respect to the time information; leap second display means for displaying a numerical value corresponding to the leap second correction value stored in the storage means; instruction receiving means for receiving an instruction operation of changing the leap second correction value from a user in a state in which the leap second display means displays the numerical value; and leap second correction value changing means for changing the leap second correction value stored in the storage means in response to the received instruction operation.
Further, the storage means may further store information relating to an expiry date of the leap second correction value, the leap second correction value changing means may update the information relating to the expiry date when changing the leap second correction value, and the radio-controlled watch may further include determination result display means for determining, with use of the information relating to the expiry date, whether the leap second correction value stored in the storage means is valid or not, and displaying a result of the determination.
Further, in the above-mentioned radio-controlled watch, the instruction receiving means may receive the instruction operation from the user in a state in which the determination result display means displays that the leap second correction value stored in the storage means is not valid, and the instruction receiving means may restrict the reception of the instruction operation in a state in which the determination result display means displays that the leap second correction value stored in the storage means is valid.
Further, the signal from the satellite may contain information relating to the leap second correction value, the radio-controlled watch may further include leap second information receiving means for receiving the signal containing the information relating to the leap second correction value from the satellite, and changing the leap second correction value stored in the storage means in accordance with the received signal, and the leap second information receiving means may update the information relating to the expiry date when extracting the information relating to the leap second correction value.
Further, in the above-mentioned radio-controlled watch, the leap second display means may display the numerical value corresponding to the leap second correction value by a combination of a second hand and a minute hand.
Further, in the above-mentioned radio-controlled watch, the instruction receiving means may receive, from the user, the instruction operation of changing the leap second correction value and also an input operation of information indicating an application time of applying the changed leap second correction value, and the leap second correction value changing means may change the leap second correction value stored in the storage means at a time corresponding to the application time.
Further, in the above-mentioned radio-controlled watch, when it is determined that the leap second correction value stored in the storage means is valid, the determination result display means may display the expiry date together with the result of the determination.
According to the radio-controlled watch of the present invention, it is possible to perform the leap second correction without receiving the information on the leap second from the satellite.
Hereinafter, embodiments of the present invention are described in detail with reference to the drawings. Note that the case where a radio-controlled watch according to the embodiments of the present invention is a wristwatch will be described below as an example.
First, a radio-controlled watch according to a first embodiment of the present invention will be described. A radio-controlled watch 1 according to this embodiment receives a satellite signal containing time information transmitted from a satellite, and adjusts time information with the use of the received satellite signal.
The antenna 10 receives a satellite signal transmitted from a satellite. In this embodiment, the antenna 10 receives a radio signal having a frequency of about 1.6 GHz transmitted from a Global Positioning System (GPS) satellite. GPS is one kind of satellite positioning system, which is realized by a plurality of GPS satellites orbiting around the earth. Those GPS satellites each carry a highly-accurate atomic clock and periodically transmit a satellite signal containing information on the time counted by the atomic clock. Note that in the following, the time indicated by the time information contained in the satellite signal is referred to as GPS time.
The reception circuit 20 decodes the satellite signal received by the antenna 10, and outputs a bit sequence (received data) indicating the contents of the satellite signal, which are obtained as a result of the decoding. Specifically, the reception circuit 20 includes a radio frequency circuit (RF circuit) 21 and a decoder circuit 22.
The radio frequency circuit 21 is an integrated circuit that operates at a high frequency. The radio frequency circuit 21 amplifies and detects an analog signal received by the antenna 10, and converts the analog signal into a baseband signal. The decoder circuit 22 is an integrated circuit that performs baseband processing. The decoder circuit 22 decodes the baseband signal output by the radio frequency circuit 21 to generate a bit sequence indicating the contents of data received from the GPS satellite, and outputs the bit sequence to the control circuit 30.
The control circuit 30 is a microcomputer or the like, and includes an arithmetic unit 31, a read only memory (ROM) 32, a random access memory (RAM) 33, a real time clock (RTC) 34, and a motor drive circuit 35.
The arithmetic unit 31 performs various kinds of information processing in accordance with a program stored in the ROM 32. The details of the processing executed by the arithmetic unit 31 in this embodiment will be described later. The RAM 33 functions as a working memory of the arithmetic unit 31, and data to be processed by the arithmetic unit 31 is written in the RAM 33. Particularly in this embodiment, the bit sequence (received data) indicating the contents of the satellite signal received by the reception circuit 20 is sequentially written into a buffer area of the RAM 33. Further, a leap second correction value LS to be used for adjusting the time information is stored in the RAM 33. The RTC 34 supplies a clock signal to be used for counting performed inside the radio-controlled watch 1. In the radio-controlled watch 1 according to this embodiment, the arithmetic unit 31 adjusts the internal time, which is counted by the signal supplied from the RTC 34, based on the satellite signal received by the reception circuit 20, and determines the time (display time) to be displayed on the time display unit 51. In addition, the motor drive circuit 35 outputs, in accordance with the determined display time, a drive signal for driving a motor included in the drive mechanism 50 to be described later. In this way, the display time generated by the control circuit 30 is displayed on the time display unit 51.
The power source 40 includes a power storage device such as a secondary battery, and stores electric power generated by the solar battery 41. The power source 40 then supplies the stored electric power to the reception circuit 20 and the control circuit 30. In particular, a switch 42 is provided in the course of a power supply path from the power source 40 to the reception circuit 20, and the switch 42 is switched between ON and OFF by a control signal output by the control circuit 30. In other words, the control circuit 30 can control an operation time of the reception circuit 20 by switching the ON/OFF state of the switch 42. The reception circuit 20 operates only in a period during which the electric power is supplied from the power source 40 via the switch 42, and decodes the satellite signal received by the antenna 10 during this period.
The solar battery 41 is disposed under a watch face 53, generates electric power using external light such as solar light radiated to the radio-controlled watch 1, and supplies the generated electric power to the power source 40.
The drive mechanism 50 includes a stepper motor that operates in accordance with the above-mentioned drive signal output from the motor drive circuit 35, and a gear train. The gear train transmits the rotation of the stepper motor, to thereby rotate indicator hands 52. The time display unit 51 includes the indicator hands 52 and the watch face 53. The indicator hands 52 include an hour hand 52a, a minute hand 52b, and a second hand 52c. Those indicator hands 52 rotate on the watch face 53, to thereby indicate the current time. Note that on the watch face 53, as illustrated in
The operating unit 60 receives an operation performed by the user of the radio-controlled watch 1, and outputs the contents of the operation to the control circuit 30. Specifically, the operating unit 60 in this embodiment includes, as illustrated in
Now, the structure of the satellite signal transmitted from the GPS satellite will be described.
The head word (Word 1) in each subframe is called a Telemetry Word (TLM), containing a preamble indicating the start position of the subframe at its header (that is, at the header of the entire subframe). The second word (Word 2) in each subframe is called a Handover Word (HOW), containing time information called Time Of Week (TOW) at its header. The TOW is time information indicating GPS time starting from the beginning of a week (Sunday at 0:00 a.m.). The radio-controlled watch 1 receives the TOW data from one or a plurality of GPS satellites, and uses a combination of the TOW data and information on a week number WN so as to know the GPS time counted by the GPS satellite. The week number WN is information indicating the number of a week to which the time indicated by the TOW belongs, and is counted up once a week every Sunday at 0:00 a.m. The information on the week number WN is transmitted from the GPS satellite in the state of being stored in Subframe 1 of each frame.
The radio-controlled watch 1 receives the TOW contained in any one of the subframes, and can therefore acquire time information transmitted by the GPS satellite. However, the GPS time indicated by the time information is deviated from Coordinated Universal Time by several integer seconds caused by the leap second. Specifically, the GPS time is deviated from Coordinated Universal Time by a period of the leap seconds accumulated after the first launch of the GPS satellite (in 1980). Therefore, the radio-controlled watch 1 is required to adjust the GPS time obtained from the GPS satellite to the time under Coordinated Universal Time with the use of the leap second information.
The information relating to the leap second necessary for the adjustment is also transmitted regularly from the GPS satellite. Specifically, in the satellite signal having 25 frames in total transmitted by the GPS satellite, the leap second information is contained in Subframe 4 of the frame of Page 18. The latter five words of the subframe (that is, 151st and subsequent bits counted from the header) are information relating to Coordinated Universal Time, and the information relating to Coordinated Universal Time contains information on an integer value to be corrected with respect to the GPS time for the leap second adjustment (hereinafter, the integer value is referred to as leap second correction value LS). The leap second correction value LS is contained only in one subframe of all pieces of navigation data, and hence is transmitted from the GPS satellite once every 12.5-minute cycle. The radio-controlled watch 1 according to this embodiment performs the leap second correction by extracting the leap second correction value LS contained in the satellite signal received from the GPS satellite. As an alternative for the case where the information on the leap second correction value LS cannot be received from the GPS satellite, the radio-controlled watch 1 is provided with a function of enabling the user to change the leap second correction value LS manually.
Note that the subframe containing the leap second correction value LS contains, in addition to the leap second correction value LS, information on the scheduled date and time of the next leap second adjustment (leap second adjustment announcement information). This information is updated when the scheduled date of implementation of the next leap second adjustment is determined, and indicates the date and time of the previous leap second adjustment until the next leap second adjustment implementation time is determined. When the leap second adjustment announcement information indicates future date and time, it is understood that the leap second correction value LS will not be changed until the indicated date and time arrive.
Hereinafter, a specific example of the processing executed by the arithmetic unit 31 of the control circuit 30 in this embodiment will be described. The arithmetic unit 31 executes the program stored in the ROM 32, to thereby functionally implement a satellite signal reception unit 31a, a leap second information management unit 31b, and a time adjustment unit 31c as illustrated in
The satellite signal reception unit 31a receives the satellite signal transmitted from the GPS satellite, to thereby acquire data on the TOW and the week number WN contained in the satellite signal. Note that, the satellite signal reception unit 31a may execute the processing of acquiring such time information regularly, or may execute the processing in response to a user's instruction operation with respect to the operating unit 60. Further, in this embodiment, the satellite signal reception unit 31a tries to receive a subframe containing the leap second correction value LS at a predetermined time. When the reception has succeeded, the satellite signal reception unit 31a extracts the leap second correction value LS from the received data, and stores the leap second correction value LS in the RAM 33.
The leap second information management unit 31b manages the leap second correction value LS stored in the RAM 33. Specifically, the RAM 33 stores the information on the leap second correction value LS and also information relating to an expiry date of the leap second correction value LS (leap second expiry date information), and the leap second information management unit 31b uses the leap second expiry date information to determine whether the leap second correction value LS stored in the RAM 33 is valid or not (that is, whether the expiry date of the leap second correction value LS has expired or not). When it is determined that the expiry date of the leap second correction value LS has expired, the leap second information management unit 31b further executes processing of updating the leap second correction value LS manually in response to a user's instruction. That is, when the expiry date of the leap second correction value LS stored in the RAM 33 has expired, the leap second information management unit 31b displays and updates the leap second correction value LS stored in the RAM 33 in response to a user's instruction operation with respect to the operating unit 60. A specific example of the processing of updating the leap second correction value LS executed by the leap second information management unit 31b will be described later.
The time adjustment unit 31c adjusts the internal time counted inside the radio-controlled watch 1 with the use of the GPS time information received from the GPS satellite by the satellite signal reception unit 31a and the leap second correction value LS stored in the RAM 33. Specifically, the time adjustment unit 31c first adds the leap second correction value LS to the GPS time to calculate time information based on Coordinated Universal Time. Then, the time adjustment unit 31c adjusts the internal time counted inside the control circuit 30 so as to coincide with the time under Coordinated Universal Time. Note that the internal time information of the radio-controlled watch 1, which is to be adjusted by the time adjustment unit 31c, is stored in the RAM 33 and is updated in accordance with the clock signal supplied from the RTC 34. In this case, the time adjustment unit 31c may adjust the time with the use of the leap second correction value LS even when the expiry date of the leap second correction value LS has expired. This is because even when the expiry date set inside the radio-controlled watch 1 has expired, the time based on Coordinated Universal Time can be calculated with the use of the leap second correction value LS stored in the RAM 33 as long as new leap second adjustment is not actually performed.
Hereinafter, the expiry date of the leap second correction value LS, which is managed by the leap second information management unit 31b, will be described. The leap second adjustment with respect to Coordinated Universal Time is performed on the last day of each month, under Coordinated Universal Time. Accordingly, for example, when the leap second correction value LS has been manually updated, the leap second information management unit 31b determines that the currently-stored leap second correction value LS is valid until at least the last day of the month where the update has been performed. Further, the adjustment of the leap second is to be performed preferentially on the last day of June and the last day of December, and is not actually performed on other days. Therefore, the leap second information management unit 31b may determine that the leap second correction value LS is valid until the last day of the next June or the last day of the next December after the leap second correction value LS has been updated. Otherwise, the leap second information management unit 31b may determine that the leap second correction value LS is valid until a predetermined period has elapsed since the update of the leap second correction value LS or until the arrival of a predetermined date and time.
As a specific method of managing the expiry date of the leap second correction value LS, for example, when the leap second correction value LS has been manually updated, in response to the update, the leap second information management unit 31b updates a leap second validity flag to a value indicating “valid”, and also updates information indicating until what month the updated leap second correction value LS is valid (information on expiry month). In this example, the leap second validity flag and the information on the expiry month are used as leap second expiry date information. As an example, in the case where the leap second correction value LS is updated on February, 2010, the leap second information management unit 31b sets June, 2010, which is the month, of June and December, whose last day comes earlier after the updated date, as an expiry month. After that, when the 1st of each month arrives, the leap second information management unit 31b compares the information on the expiry month to the information on the internal time based on Coordinated Universal Time, which is stored in the RAM 33, to thereby determine whether the expiry month has passed or not. In the above-mentioned example, when Jul. 1, 2010, under Coordinated Universal Time arrives, it is determined that the expiry date of the leap second correction value LS has expired. In this case, the leap second information management unit 31b switches the leap second validity flag from the value indicating “valid” to a value indicating “invalid”. By referring to the value of the leap second validity flag, the leap second information management unit 31b determines whether the currently-stored leap second correction value LS is valid or not.
Note that in this example, when the leap second correction value LS can be received from the GPS satellite by the satellite signal reception unit 31a, the leap second information management unit 31b may update the information on the expiry month by referring to the leap second adjustment announcement information which is transmitted from the GPS satellite together with the leap second correction value LS. That is, when the leap second adjustment announcement information indicates future date and time, the month corresponding to the date is set as the expiry month. With this configuration, the leap second information management unit 31b can determine whether the currently-stored leap second correction value LS is valid or not by referring to the information on the expiry month, irrespective of whether the reception of the leap second correction value LS has succeeded or not in the past. In this case, when the leap second adjustment announcement information indicates past date and time (that is, the next leap second adjustment implementation time is still unknown), the leap second information management unit 31b may update the expiry date information by a rule similar to that in the case where the leap second correction value LS has been manually updated.
As another example of the method of managing the leap second expiry date, in the case where the leap second correction value LS is set so as to expire on the last day of the month where the leap second correction value LS has been manually updated, the leap second information management unit 31b does not need to keep information on the expiry month. In this case, the leap second information management unit 31b manages the expiry date with the use of only the leap second validity flag as leap second expiry date information. That is, when the leap second correction value LS has been manually updated, the leap second validity flag is set to “valid”, and when the 1st day of each month arrives, the leap second validity flag is changed to “invalid”. With this, the leap second correction value LS which had been updated the previous month can be made invalid at the beginning of each month.
Note that in this example, the leap second information management unit 31b may change the method of managing the expiry date in accordance with whether the previous leap second correction value LS has been updated manually or updated by the reception of the satellite signal. Specifically, the leap second information management unit 31b further keeps, in the RAM 33, flag information indicating whether the previous leap second correction value LS has been manually updated or not. When the 1st day of each month arrives, if it is determined from the flag information that the previous update was performed manually, the leap second validity flag is changed to “invalid”. On the other hand, if it is determined that the previous update was not performed manually but by the reception of the satellite signal, for example, similarly to the above-mentioned example, the leap second validity flag is updated based on the leap second adjustment announcement information received together with the leap second correction value LS.
As still another example of the method of managing the leap second expiry date, the leap second information management unit 31b may manage the expiry date of the leap second correction value LS with the use of a counter value indicating how much longer the leap second correction value LS is valid as the expiry date information. This counter value is information indicating the remaining valid period of the leap second correction value LS in predetermined time units, such as by hours, by days, and by months. As an example, in the case where the expiry date of the leap second correction value LS is managed with the use of a counter value to be counted by hours, the leap second information management unit 31b initializes the counter value to a predetermined value when the leap second correction value LS is manually updated. For example, when the expiry date of the leap second correction value LS is 30 days, the counter value is set to 720 (=30×24). After that, every hour, the leap second information management unit 31b updates the counter value to a value decremented by 1. Accordingly, the counter value gradually decreases with time, finally reaching 0 after the lapse of 720 hours. After the counter value becomes 0, the leap second information management unit 31b does not perform processing of decrementing the counter value any more. Then, when the counter value is 0, it is determined that the leap second correction value LS is not valid. Note that in this example, the leap second information management unit 31b may change the leap second validity flag to “invalid” at the time when the counter value becomes 0, or may determine whether the leap second correction value LS is valid or not based on whether the counter value is 0 or not, instead of using the leap second validity flag. Note that in this case also, if the leap second correction value LS has been updated by the reception of the satellite signal, a time period until the next leap second adjustment implementation time may be calculated based on the leap second adjustment announcement information, which has been received together with the leap second correction value LS, so as to set the counter value in accordance with the calculated value.
Next, an exemplary operation procedure of updating the leap second correction value LS by the radio-controlled watch 1 will be described with reference to
First, in a normal time display state M1 in which the current date and time are displayed by the indicator hands 52 as illustrated in part (a) of
In the leap second expiry display state M2, when the user presses the first operation button S1 again, the radio-controlled watch 1 returns to the time display state M1, and brings the second hand 52c back to the position corresponding to the current time. In the case where the leap second correction value LS is valid, it is not necessary to update the leap second correction value LS, and hence the user only needs to press the first operation button S1 so that the radio-controlled watch 1 may return to the time display state M1. Note that also in the case where the user has performed no operation for a predetermined period since the transition to the leap second expiry display state M2, the radio-controlled watch 1 automatically returns to the time display state M1. On the other hand, in the case where the expiry date of the leap second correction value LS has expired, the user selects whether to press the second operation button S2 to cause the radio-controlled watch 1 to execute the reception of the leap second information or perform an operation of pulling out the crown S3 to manually update the leap second information.
In the leap second expiry display state M2, when the user presses the second operation button S2, the radio-controlled watch 1 makes a transition to a leap second receiving state M3. In this state, the satellite signal reception unit 31a tries to receive a satellite signal containing a leap second correction value LS transmitted from a GPS satellite. In this case, as illustrated in part (d) of
After that, when the reception of the leap second correction value LS has succeeded, the leap second information management unit 31b stores the received leap second correction value LS in the RAM 33 and resets the expiry date of the leap second correction value LS, and the time adjustment unit 31c performs time correction processing with the use of the leap second correction value LS newly received. Then, in order to notify the user that the reception of the leap second correction value LS has succeeded, the radio-controlled watch 1 moves the second hand 52c to the position indicating “LS-OK” and temporarily stops the second hand 52c at this position as illustrated in part (e) of
On the other hand, when the reception of the leap second correction value LS has failed, the radio-controlled watch 1 returns to the time display state M1 without updating the leap second correction value LS. Note that in
In the leap second expiry display state M2, when the user performs the operation of pulling out the crown S3, the radio-controlled watch 1 makes a transition to a leap second manual adjustment state M4. In this state, as illustrated in part (g) of
The display method illustrated in part (g) of
Note that in the leap second manual adjustment state M4, the leap second information management unit 31b can display the numerical value of the leap second correction value LS as it is, but may display a numerical value corresponding to the leap second correction value LS by adding or subtracting a predetermined numerical value to or from the numerical value of the leap second correction value LS. As described above, GPS time information received by the radio-controlled watch 1 according to this embodiment is deviated from Coordinated Universal Time by a period corresponding to the leap seconds accumulated after Jan. 1, 1980. As of Jan. 1, 1980, a deviation of 19 seconds was present between International Atomic Time and Coordinated Universal Time. It follows that a difference of 19 seconds is always present between GPS time and International Atomic Time. Therefore, the leap second correction value LS for adjusting the GPS time to Coordinated Universal Time is smaller by 19 seconds than a correction amount for adjusting International Atomic Time to Coordinated Universal Time. In light of this, the leap second information management unit 31b may display a value obtained by adding 19 seconds to the leap second correction value LS on the time display unit 51. Specifically, in the example of part (g) of
Alternatively, the leap second information management unit 31b may display the leap second correction value LS as a relative value with respect to the initial value thereof (for example, the leap second correction value LS stored in the ROM 32 at the time of shipment of the radio-controlled watch 1).
Further, in the state transition diagram of
Further, although not illustrated in
Now, control to be performed when the system of the radio-controlled watch 1 is restarted will be described. For example, in the case where the power supply voltage of the power source 40 has reduced and it becomes difficult to continue the operation, the radio-controlled watch 1 may execute processing of saving information in the RAM 33 into a non-volatile memory before system-down occurs, and normally terminating the control circuit 30. Alternatively, system reset of the control circuit 30 may be executed. In the case where such processing is executed and the control circuit 30 is thereafter restarted, the arithmetic unit 31 reacquires the leap second information as a part of start processing. Specifically, as illustrated in the state transition diagram of
Further, instead of making a transition to the leap second receiving state M3 or the leap second manual adjustment state M4 immediately after the restart, the radio-controlled watch 1 may refer to the leap second expiry date information at the previous time when the operation of the system stopped to determine whether the expiry date of the leap second correction value LS has expired or not, and may make a transition to the leap second receiving state M3 or the leap second manual adjustment state M4 as described above only when it is determined that the expiry date of the leap second correction value LS has expired. In this case, after the restart, the radio-controlled watch 1 first receives the data on the TOW and the week number WN to acquire information on the current date and time. Then, the radio-controlled watch 1 refers to the information on the current date and time and the leap second expiry date information to determine whether the expiry date of the leap second correction value LS has expired or not. When the expiry date of the leap second correction value LS has not expired, the radio-controlled watch 1 makes a transition to the time display state M1 to start normal time display.
According to the radio-controlled watch 1 of this embodiment described above, the leap second can be manually set, and hence, even when the reception of the leap second has not succeeded, the leap second information can be acquired and used for adjusting the time information received from the satellite signal. As described above, the transmission frequency of the leap second information from the GPS satellite is lower than that of the TOW and the like, and hence the chance of receiving the leap second information is restricted. Particularly in a portable watch such as a wristwatch, in some cases, a good reception condition cannot be ensured stably, and the leap second information cannot be received for a long time. According to the radio-controlled watch 1 of this embodiment, in such a case, the user can set the leap second manually as an alternative. In addition, when the setting of the leap second by the user is received, the expiry date is set with respect to the leap second information, and when the expiry date has expired, the user is notified of the expiation. Therefore, the user can easily know whether the leap second information needs to be reset or not.
Next, a radio-controlled watch according to a second embodiment of the present invention will be described. Note that the radio-controlled watch according to this embodiment is different from the radio-controlled watch according to the first embodiment in internal processing, but the hardware configuration and functional configuration may be the same as those in the first embodiment. Therefore, in the following, the same components as those in the first embodiment are denoted by the same reference symbols, and the detailed descriptions thereof are omitted.
In this embodiment, the satellite signal reception unit 31a acquires information on the TOW and the week number WN contained in a satellite signal, but does not receive information on the leap second correction value LS. In the ROM 32, an initial value of the leap second correction value LS is stored at the time of shipment, and the leap second information management unit 31b first reads the initial value and stores the initial value in the RAM 33. The leap second correction value LS stored in the RAM 33 is changed by manual updating by the user similarly to the first embodiment. The time adjustment unit 31c corrects the GPS time obtained from the TOW to the time based on Coordinated Universal Time with the use of the leap second correction value LS stored in the RAM 33.
Now, an exemplary operation procedure of updating the leap second correction value LS by the radio-controlled watch 1 in this embodiment will be described with reference to
First, in the normal time display state M1 in which the current date and time are displayed by the indicator hands 52 as illustrated in part (a) of
In the leap second expiry display state M2, when the user presses the first operation button S1, or when the predetermined period has elapsed while the user performs no operation, similarly to the first embodiment, the radio-controlled watch 1 returns to the time display state M1. On the other hand, when the expiry date of the leap second correction value LS has expired, the user performs an operation of pulling out the crown S3 to update the leap second information manually. The radio-controlled watch 1 according to this embodiment does not support the reception of the leap second information, and hence, unlike the first embodiment, the radio-controlled watch 1 cannot make a transition to the leap second receiving state M3 through the operation of the second operation button S2.
In the leap second expiry display state M2, when the user performs the operation of pulling out the crown S3, the radio-controlled watch 1 makes a transition to the leap second manual adjustment state M4. In this state, as illustrated in part (d) of
Note that similarly to the first embodiment, when returning from the system reset state M5, the radio-controlled watch 1 according to this embodiment may also make a transition to the leap second manual adjustment state M4 in accordance with the state of the crown S3 at the time of the return. In this case, as illustrated in the state transition diagram of
According to the radio-controlled watch 1 of this embodiment described above, the processing of receiving the leap second is not performed in the first place, and hence it is unnecessary to notify the user of an event such as a failure of reception of the leap second, thus making the operation easily understandable by the user. Further, power consumption due to the processing of receiving the leap second can be avoided. On the other hand, although the function of receiving the leap second is not provided, the manual setting of the leap second is received, and hence, when the leap second adjustment is performed, it is possible to display the time based on Coordinated Universal Time reflecting the contents of the leap second adjustment. Note that at present, the implementation frequency of the leap second adjustment is not so high, and hence, even if the user needs to set the leap second manually, not so much time and effort is required for the user.
The embodiments of the present invention are not limited to the ones described above. For example, the radio-controlled watch 1 in the above description is a wristwatch, but instead, may be various kinds of clock that adjust time by receiving a signal containing time information from a satellite. Besides, at least part of the processing to be executed by the arithmetic unit 31 of the control circuit 30 in the above description may be implemented by an independent arithmetic circuit, such as a logic circuit.
Further, the form of displaying whether the expiry date of the leap second correction value LS has expired or not and the form of displaying the numerical value corresponding to the leap second correction value LS, which are performed by the radio-controlled watch 1 according to the above-mentioned embodiments, are each an example. The radio-controlled watch according to the embodiments of the present invention may display those pieces of information in various different kinds of display form. For example, when the expiry date of the leap second correction value LS has expired, the radio-controlled watch 1 may display the expiration of the expiry date to a user by a method such as two-second interval movement. Further, the procedure of the instruction operation performed by the user when the processing of updating the leap second is performed may be various kinds of procedure other than the one described above.
Hereinafter, another display example of displaying, by the radio-controlled watch 1 according to the embodiments of the present invention, a numerical value corresponding to the leap second correction value LS in the above-mentioned leap second manual adjustment state M4 will be described. Note that in the following, a numerical value to be displayed and to be adjusted by a user in the leap second manual adjustment state M4 is referred to as an adjustment target value. As described above, the adjustment target value may be the leap second correction value LS itself, or may be a value obtained by adding a predetermined value (such as a value indicating a deviation between GPS time and International Atomic Time) to the leap second correction value LS.
For example, the radio-controlled watch 1 may display the leap second correction value LS by a combination of the minute hand 52b and the second hand 52c. A first specific example in this case is that the radio-controlled watch 1 indicates the ones place value and the tens place value of the adjustment target value by the position of the second hand 52c and the position of the minute hand 52b, respectively.
In this case, the radio-controlled watch 1 may also display a rollover counter value using the position of the hour hand 52a. Here, the rollover counter value indicates the number of overflows of the above-mentioned week number WN since a predetermined start time. The week number WN contained in information transmitted by the GPS satellite is 10-bit information, whose maximum value is 1,023. Therefore, the week number WN overflows to be reset to 0 every 1,024 weeks (about 20 years). As a countermeasure, the radio-controlled watch 1 is sometimes provided with a rollover counter function of counting the number of overflows. In this case, the radio-controlled watch 1 adds 1 to the rollover counter value when the week number WN overflows. With this, even when the radio-controlled watch 1 is used for a long time of 20 years or more, it is possible to know which week, counted from the predetermined start time, the current time falls on, by a combination of the rollover counter value and the week number WN. Then, the calendar date can be displayed based on this information. In the display example of
However, in the case where the radio-controlled watch 1 provided with the rollover counter function has stopped for a long time including an overflow time of the week number WN, the rollover counter value cannot be counted up when the week number WN overflows, and it becomes impossible to know which week the current time falls on. As a countermeasure against such a case, as illustrated in
Further, the radio-controlled watch 1 may display the adjustment target value with the use of other indicator hands than the hour hand 52a, the minute hand 52b, and the second hand 52c for time display.
Further, in the example of
Further, in the case of displaying that the leap second correction value LS is valid in the leap second expiry display state M2, the radio-controlled watch 1 may also display how long the leap second correction value LS is valid for (that is, when the expiry date of the leap second correction value LS expires). In this case, the radio-controlled watch 1 performs display as exemplified in
In addition, in the above description, in the states of part (b) of
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-073857 | Mar 2010 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2011/056982 | 3/23/2011 | WO | 00 | 9/12/2012 |
