Time Adjustment Device, Timepiece with a Time Adjustment Device, and Time Adjustment Method

CROSS-REFERENCE TO RELATED APPLICATIONS

Japanese Patent application No. 2007-002726 is hereby incorporated by reference in its entirety.

BACKGROUND

1. Field of Invention

The present invention relates to a time adjustment device that adjusts the time based on time information contained in signals transmitted from the base station of a CDMA (Code Division Multiplex Access) cell phone network, for example. The invention also relates to a timepiece having the time adjustment device, and to a time adjustment method.

2. Description of Related Art

Time information is contained in signals transmitted to cell phones from the base stations in modern CDMA cell phone networks. This time information is extremely precise time information that matches the GPS time, which is based on the atomic clocks on GPS (Global Positioning System) satellites.

Japanese Unexamined Patent Appl. Pub. JP-A-2000-321383 (see the abstract) teaches a terminal that acquires the GPS time data transmitted from a base station of a CDMA cell phone network, and uses the GPS time data to correct the time kept by an internal clock.

However, the time data transmitted from the base stations of a CDMA cell phone network is the time after a prescribed amount of time has passed after the transmission, and is not the time of the actual transmission.

This allows for time synchronization after data processing by the cell phone that receives the time data. More specifically, a cell phone that gets time data from the base station must internally prepare to synchronize with the signals from the base station, and after this preparation is completed the cell phone synchronizes the time with the base station signal based on the received time data.

In other words, if the time data that is sent from the base station is used as the reception time, there is not enough internal processing time for time synchronization, synchronization is therefore not possible, and communication is therefore not possible as a result.

The time data transmitted from the base stations of a CDMA cell phone network is therefore the time at a prescribed time after the transmission, and the cell phone is designed to receive this future time.

However, if this future time is received and used for time adjustment, time adjustment must wait for this future time to arrive because the received time is not the time when the time information is received, the receiver side must continue communication with the base station until this future time arrives, and power consumption therefore increases.

Furthermore, the signals containing the time data transmitted from base stations on a CDMA cell phone network are transmitted in frames at a prescribed fixed interval and must be received in frame units, and the cell phone must communicate with the base station for a prescribed time. However, the length of the signal containing this time data does not necessarily coincide with the length of the frame in this fixed interval, and the end of the signal containing the time data may not coincide with the end of the frame. Null data is therefore added as padding after the end of the time data signal. Furthermore, while this padding is not needed as part of the signal containing the time data, the padding is received for a prescribed time to the end of the frame.

Power consumption therefore increases commensurately.

A receiver with such high power consumption therefore cannot be incorporated in devices with very low power requirements, such as timepieces, and timepieces and other such devices therefore cannot adjust the time with high precision.

SUMMARY

A time adjustment device, the timepiece having the time adjustment device, and the time adjustment method of the invention enable adjusting the time with high precision without high power consumption even when very little power is required.

A time adjustment device according to a first aspect of the invention has a reception unit that receives a prescribed signal containing time information transmitted by a base station, and a display time information adjustment unit that adjusts the time information displayed by a time information display unit based on the time information. The prescribed signal is transmitted from the base station to correspond to frame information at a fixed interval, and the reception unit includes an identification information acquisition unit that gets identification information identifying the length of the prescribed signal, and a prescribed signal reception stopping unit that stops reception at the end of the prescribed signal based on the identification information.

In this aspect of the invention the prescribed signal is transmitted from the base station to correspond to frame information at a fixed interval, the reception unit includes an identification information acquisition unit that gets identification information identifying the length of the prescribed signal and a prescribed signal reception stopping unit that stops reception at the end of the prescribed signal based on the identification information, and the display time information adjustment unit adjusts the time information displayed by a time information display unit based on the time information.

The time adjustment device can thus get the time information in a short time when acquiring the time information, and stops the reception unit immediately at the end of the prescribed signal. Power consumption can therefore be reduced, high precision time information can be acquired in a short time, and the time can be adjusted with high precision.

Preferably, identified time difference information that is converted by an identified time difference information conversion unit from the identification information based on basic conversion time data is time information from the end of the prescribed signal to the end of the frame information that contains the end of the prescribed signal, and the display time information adjustment unit adjusts the displayed time information to reflect the identified time difference information.

With this aspect of the invention the identified time difference information is converted by an identified time difference information conversion unit from the identification information based on basic conversion time data, and the display time information adjustment unit reflects the identified time difference information when adjusting the time.

This identified time difference information is the time difference from the end of the prescribed signal to the end of the frame information that contains the end of the prescribed signal, is converted and acquired from the identification information, and when adjusting the time enables shortening the time adjustment time by the identified time difference while also adjusting the time accurately.

Further preferably, the basic conversion time data is compiled in a basic conversion time data table containing plural records of identification information and corresponding identified time difference information.

Because the basic conversion time data is compiled in a basic conversion time data table containing plural records of identification information and corresponding identified time difference information, the identified time difference information can be immediately extracted and converted once the identification information is acquired. Furthermore, because the identification information and identified time difference information are stored together, the time can be adjusted immediately when adjusting the time according to the identification information.

Yet further preferably, the basic conversion time data is obtained by a calculation allocating an information unit time to the identification information.

Because the basic conversion time data is obtained by a calculation allocating an information unit time to the identification information, once the identification information is obtained this aspect of the invention can immediately calculate the identified time difference information, calculate the identified time difference information for the specific identification information, and adjust the time.

Further preferably, the time adjustment device also has a leap seconds information storage unit for storing leap seconds information that is time adjustment information based on rotation of the Earth and is contained in the time information, and a leap seconds application time information storage unit that stores leap seconds application time information for adjusting the displayed time information based on the leap seconds information, and the display time information adjustment unit corrects the displayed time information based on the leap seconds information and the leap seconds application time information.

This aspect of the invention has a leap seconds information storage unit for storing leap seconds information that is time adjustment information based on rotation of the Earth and is contained in the time information, and a leap seconds application time information storage unit that stores leap seconds application time information for adjusting the displayed time information based on the leap seconds information, and the display time information adjustment unit corrects the displayed time information based on the leap seconds information and the leap seconds application time information.

As a result, if the time adjustment device gets the leap seconds information before the leap seconds information should be used, the received leap seconds information is not used immediately to adjust the displayed time information and the displayed time information is instead adjusted based on the leap seconds information when the leap seconds information is to be used.

The leap seconds information acquired from the base station can therefore be accurately reflected in the time adjustment.

In another aspect of the invention the time information is future time information for a specific time after the reception time information, which is the time the reception unit receives, and the time adjustment device also has a time difference information storage unit that stores the time difference between the future time information and the reception time information, a reception time information generating unit that generates the reception time information of the reception unit based on the future time information received by the reception unit and the time difference information, and an adjustment time information generating unit that generates adjustment time information for adjusting the display time information adjustment unit based on the reception time information generated by the reception time information generating unit and at least processing time information for the time adjustment device.

Another aspect of the invention is a timepiece device having a time adjustment device, including a reception unit that receives a prescribed signal containing time information transmitted by a base station, and a display time information adjustment unit that adjusts the time information displayed by a time information display unit based on the time information. The prescribed signal is transmitted from the base station to correspond to frame information at a fixed interval, and the reception unit includes an identification information acquisition unit that gets identification information identifying the length of the prescribed signal, and a prescribed signal reception stopping unit that stops reception at the end of the prescribed signal based on the identification information.

Another aspect of the invention is a time adjustment method for a time adjustment device including a reception unit that receives a prescribed signal containing time information transmitted by a base station, and a display time information adjustment unit that adjusts the time information displayed by a time information display unit based on the time information. The time adjustment method includes an identification information acquisition step of the reception unit getting identification information identifying the length of the prescribed signal that is transmitted from the base station to correspond to fixed interval frame information, and a prescribed signal reception stopping step of stopping reception at the end of the prescribed signal based on the identification information.

Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing a wristwatch with a time adjustment device as an example of a timepiece having a time adjustment device according to the invention.

FIG. 2 is a schematic diagram showing the main internal hardware arrangement of the wristwatch shown in FIG. 1.

FIG. 3 is a schematic diagram showing the basic arrangement of the CDMA base station signal receiver shown in FIG. 2.

FIG. 4 is a schematic diagram showing the main software configuration of the wristwatch.

FIG. 5 is a schematic diagram showing data stored in the program storage unit in FIG. 4.

FIG. 6 is a schematic diagram showing data stored in the first data storage unit in FIG. 4.

FIG. 7 is a schematic diagram showing data stored in the second data storage unit in FIG. 4.

FIG. 8 is a flow chart describing the main operation of the wristwatch according to the invention.

FIG. 9 is flow chart describing the main operation of the wristwatch according to the invention.

FIG. 10 is flow chart describing the main operation of the wristwatch according to the invention.

FIG. 11 describes the synchronization timing of signals transmitted from a CDMA base station.

FIG. 12 is a schematic diagram describing the content of the sync channel message.

FIG. 13A is a schematic diagram describing the CDMA base station signal receiver synchronizing with the pilot channel signal, and FIG. 13B is a schematic diagram describing the relationship between the start timing and a divide-by-64 counter.

FIG. 14 is a schematic diagram describing the process of the frequency division counter frequency dividing the 1.2288 MHz chip rate of the pilot PN to generate Walsh code (32).

FIG. 15 is a table showing an example of message lengths and message length offset times in a preferred embodiment of the invention.

FIG. 16 shows an example of the pilot channel signal and the sync channel message.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of the present invention is described below with reference to the accompanying figures.

The embodiment described below has various technically desirable limitations because it is a specific preferred embodiment of the invention, but the scope of the invention is not limited to the following embodiment unless some aspect described below is specifically said to limit the invention.

FIG. 1 is a schematic diagram showing a wristwatch with a time adjustment device 10 (referred to below as simply a wristwatch) as an example of a timepiece with a time adjustment device according to the present invention, and FIG. 2 is a block diagram describing the main internal hardware configuration of the wristwatch 10 shown in FIG. 1.

As shown in FIG. 1 the wristwatch 10 has a dial 12 on the face, hands 13 including a long hand and a short hand, and a display 14 such as an LED for displaying messages. The display 14 could be an LCD or analog display, for example, instead of an LED.

As also shown in FIG. 1 the wristwatch 10 has an antenna 11, and this antenna 11 is arranged to receive signals from a base station such as CDMA base stations 16a and 15b. More specifically, these CDMA base stations 16a and 15b are base stations on a CDMA cell phone network.

The wristwatch 10 in this embodiment of the invention does not have a cell phone function and therefore does not enable voice communication with the CDMA base stations 16a, but receives time information, for example, from the signals transmitted from the CDMA base stations 16a and adjusts the time based on these received signals. The content of the signals from the CDMA base stations 16a is further described below.

As also shown in FIG. 1 the wristwatch 10 has a crown 28 that can be operated by the user.

This crown 28 is an example of an external input unit that can be operated by the user.

The hardware arrangement of the wristwatch 10 is described next.

As shown in FIG. 2 the wristwatch 10 has a bus 20, and a CPU (central processing unit) 21, RAM (random access memory) 22, and ROM (read-only memory) 23 are connected to the bus 20.

A reception unit for receiving signals from the CDMA base stations 16a, such as CDMA base station signal receiver 24, is connected to the bus 20. The CDMA base station signal receiver 24 has the antenna 11 shown in FIG. 1.

A real-time clock (RTC) 25 that is a timekeeping mechanism rendered as an IC device (semiconductor integrated circuit), for example, and a crystal oscillator with temperature compensation circuit (TCXO) 26, are also connected to the 20.

The dial 12 and hands 13 shown in FIG. 1, and the RTC 25 and TCXO 26 in FIG. 2 are thus an example of a time information display unit for displaying time information.

A battery 27 is also connected to the bus 20, and the battery 27 is a power supply unit for supplying power for communication by the reception unit (such as the CDMA base station signal receiver 24).

The display 14 and the crown 28 shown in FIG. 1 are also connected to the bus 20. The bus 20 is thus an internal bus that has a function for connecting all of the other devices and has addresses and data paths. The RAM 22 is used as working memory by the CPU 21 for executing specific programs and controlling the ROM 23 connected to the bus 20. The CPU21 executes specific programs and controls the ROM 23 connected to the bus 20. The ROM 23 stores programs and data.

FIG. 3 is a schematic diagram showing the basic arrangement of the CDMA base station signal receiver 24 shown in FIG. 2. As shown in FIG. 3 a high frequency receiver 16 is connected to the antenna 11. This high frequency receiver 16 down-converts signals received by the antenna 11 from the CDMA base stations 15a, for example.

A baseband unit 17 is also connected to the high frequency receiver 16. Inside the baseband unit 17 is a pilot PN synchronization unit 17a. This pilot PN synchronization unit 17a mixes the pilot PN code with the pilot channel signal downloaded by the high frequency receiver 16 for signal synchronization.

A start timing generator 17b is also connected to the pilot PN synchronization unit 17a. The pilot PN synchronization unit 17a inputs the timing at which the signal was synchronized to the start timing generator 17b, and based on this input the start timing generator 17b generates the start timing.

As shown in FIG. 3 the start timing generator 17b is connected to a divide-by-64 counter 17c. The start timing generated by the start timing generator 17b is thus input to the divide-by-64 counter 17c and frequency division starts.

As further described below, the divide-by-64 counter 17c divides the frequency of the pilot PN chip rate, that is, 1.2288 MHz, by 64 and generates Walsh code (32). The resulting Walsh code (32) is mixed with the sync channel signal received by the antenna 11 to extract the time information. Processing these signals is described below.

The start timing generator 17b is an example of a start timing supply unit that supplies the start timing at which the divide-by-64 counter 17c starts frequency dividing the base frequency of, for example, the pilot PN chip rate (1.2288 MHz).

The divide-by-64 counter 17c is a frequency division counter unit that frequency divides the basic unit of a prescribed signal, such as the 1.2288 MHz frequency of the pilot PN signal, and generates a time information extraction signal, such as Walsh code (32).

The baseband unit 17 also has a digital filter 17d and a deinterleaving and decoding unit 17e as shown in FIG. 3. That is, the signal received by the antenna 11 passes the digital filter 17d and then the deinterleaving and decoding unit 17e after mixing the Walsh code (32) as described above, is demodulated, and is extracted as the sync channel message described below.

FIG. 4 to FIG. 7 are schematic diagrams showing the main software arrangement of the wristwatch 10. FIG. 4 is an overview.

As shown in FIG. 4 the wristwatch 10 has a control unit 29, and the control unit 29 runs the programs stored in the program storage unit 30 shown in FIG. 4 and processes the data in the first data storage unit 40 and the data in the second data storage unit 50.

Note that the program storage unit 30, the first data storage unit 40, and the second data storage unit 50 are shown separately in FIG. 4, but in practice the data is not stored in separate devices and is shown this way for descriptive convenience only.

In addition, primarily data that is predefined is stored in the first data storage unit 40 in FIG. 4. In addition, primarily data that results from processing the data in the first data storage unit 40 by running the programs shown in the program storage unit 30 is stored in the second data storage unit 50.

FIG. 5 is a schematic diagram showing the data stored in the program storage unit 30 in FIG. 4, and FIG. 6 is a schematic diagram showing the data stored in the first data storage unit 40 in FIG. 4. FIG. 7 is a schematic diagram showing the showing the data stored in the second data storage unit 50 in FIG. 4.

FIG. 8 to FIG. 10 are flow charts describing the main operation of the wristwatch 10 according to this embodiment of the invention.

While describing the operation of the wristwatch 10 according to this embodiment of the invention with reference to the flow charts in FIG. 8 to FIG. 10, the programs and data related to this operation and shown in FIG. 5 to FIG. 7 are also described below.

Before proceeding to the description of the flow charts, the parts of the CDMA cell phone system that are related to the invention are described below.

The CDMA cell phone system started actual operation after the system developed by Qualcomm, Inc. of the United States was adopted in 1993 as the IS95 cell phone standard in the United States. This standard was later revised as IS95A, IS95, and then CDMA2000. A cell phone system conforming to ARIB STD-T53 is used in Japan.

Because the CDMA system is synchronized on the downlink (from the CDMA base station 16a to the mobile station, wristwatch 10 in this embodiment of the invention), the wristwatch 10 must synchronize with the signals from the CDMA base station 16a. The signals transmitted from the CDMA base station 16a include a pilot channel signal and a sync channel signal. The pilot channel signal is a signal that is transmitted from each CDMA base station 16a at a different timing, such as the pilot PN signal.

FIG. 11 is a timing chart of the synchronization timing for signals transmitted from the CDMA base stations 16a and 15b.

Because the signals transmitted form the CDMA base stations 16a and 15b are the same, the signal transmission timing of each CDMA base station 16a differs from the signal transmission timing of each other CDMA base station 16a so that it can be determined which CDMA base station 16a transmitted a particular signal.

More specifically, these timing differences are expressed by differences in the pilot PN signal transmitted by the CDMA base station 16a. In FIG. 11, for example, the CDMA base station 15b transmits signals at a timing delayed slightly from the CDMA base station 16a. More specifically, there is a pilot PN offset of 64 chips (0.052 ms).

By each CDMA base station 16a providing a different pilot PN offset that is an integer multiple of 64 chips, the wristwatch 10 can easily determine the CDMA base station 16a from which a signal was received even when there are many CDMA base stations 16a.

The signals transmitted from the CDMA base station 16a also contain a sync channel signal, which is the sync channel message shown in FIG. 12. FIG. 12 shows the content of the sync channel message.

As shown in FIG. 12, the sync channel message contains data about the pilot PN signal, such as data showing that the pilot PN offset is 64 chips (0.052 ms)×N (0-512). This value is contained in the PILOT_PN field in FIG. 12.

The sync channel message also contains system time information, which is the GPS time.

The system time is the cumulative time in 80 ms units from 0:00 on Jan. 6, 1980. This value is contained in the SYS_TIME field in FIG. 12.

The sync channel message also contains a leap second value for UTC (Universal Time Code) conversion. This value is contained in the LP_SEC field in FIG. 12. For example, this is a value such as “13” seconds or “14” seconds. This leap seconds value is an example of leap seconds information that is time adjustment information contained in the time information and based on the rotation of the Earth, for example.

The sync channel message also contains the local offset time, which is the time difference between the country or region where the wristwatch 10 is located and the UTC. If the country is Japan, for example, a value indicating that the time difference to UTC is +9 hours is stored.

This value is stored in the LTM_OFF field in FIG. 12.

The sync channel message also contains a daylight savings time value indicating if the country or region where the wristwatch 10 is located uses daylight savings time. The value in this example is 0 because Japan does not use daylight savings time. This value is stored in the DAYLT field in FIG. 12.

The pilot PN signal data shown in FIG. 12 is thus base station time difference information for signals transmitted from a particular base station (such as CDMA base station 15a), and the local offset information is region time conversion information for converting to the local time. The daylight savings time data is seasonal time information for converting to the time of the current season.

While the sync channel message shown in FIG. 12 contains data such as described above, the data is transmitted sequentially on the time base. The transmitted signals are transmitted in 80-ms superframe units as shown in FIG. 11, and the last superframe shown in FIG. 11 is the superframe that contains the last data in one sync channel message. The timing of the end of the last superframe in FIG. 11 (the parts denoted E and EE in FIG. 11) is thus the timing of the end of sync channel message reception.

The last superframe may not be filled completely with data, however. More specifically, as shown in FIG. 16, if the sync channel message data ends before the end of the last superframe, the superframe is padded with zeroes to the end of the superframe. The signal is then received to the end of the last superframe (denoted by E and EE in FIG. 11), which is the timing of the end of sync channel message reception.

As shown in FIG. 11, while the actual sync channel message data ends at the parts indicated by G and GG, the signal is received to the parts indicated by E and EE in FIG. 11.

Signal reception therefore continues even though there is no data actually in the sync channel message. This part that is padded with 0s instead of sync channel message data from the end of the sync channel message data to the end of the last superframe is labelled message length offset data (or Message Length OFF_SET) in FIG. 11 and FIG. 16.

The GPS time in the sync channel message shown in FIG. 12 is not the time at time E in FIG. 11 in the CDMA system, but is the time four superframes (320 ms) later, that is, at time F in FIG. 11.

More specifically, the GPS time is the time at four superframes from the time at the end of the last superframe referenced to the time when the above-described pilot PN offset is 0 chips (0 ms).

This is based on CDMA being a cell phone telecommunication system. More specifically, after the cell phone receives the sync channel message shown in FIG. 12 from a CDMA base station 15a, the cell phone needs to prepare internally for synchronized communication with the CDMA base station 15a.

That is, after preparing to shift to the next stage, standby, the cell phone synchronizes and communicates with the CDMA base station 15a.

Considering this preparation time, if the CDMA base stations 15a are arranged to send a time in the future, such as the time 320 ms after the end of the last superframe, in advance of that time so that the cell phone that continues receiving to the end of the last superframe after the end of the sync channel message data and receives this time can execute an internal process to prepare for communication and then attempt to synchronize with the CDMA base station 15a, synchronization is easier. In other words, these four superframes (320 ms) are preparation time for the cell phone. As a result, reception must continue to the end of the last superframe even though no data is contained in the sync channel message.

The CDMA cell phone system used by this embodiment of the invention is described above, and the embodiment of the invention is described below with reference to this CDMA cell phone system.

To adjust the time of the wristwatch 10, the CDMA base station signal receiver 24 shown in FIG. 2 of the wristwatch 10 scans the pilot channel in order to receive the pilot channel signal from among the signals transmitted from the CDMA base station 16a shown in FIG. 1.

Then, in ST2, the CDMA base station signal receiver 24 receives the pilot channel signal from the CDMA base station 16a. More specifically, the pilot channel signal reception program 31 in FIG. 5 operates.

The pilot PN code is then mixed with the received pilot channel signal to synchronize in ST3 in FIG. 8 and Walsh code (0) is overlayed (despreading) to get the data.

More specifically, the pilot PN synchronization program 32 in FIG. 5 operates, and the pilot PN synchronization unit 17a in FIG. 3 mixes the pilot PN code 41a stored in the pilot PN code storage unit 41 shown in FIG. 6 (the same code as the pilot PN code sent from the CDMA base station 16a) and Walsh code (0) as shown in FIG. 3 to synchronize. Preparing a special code is not necessary at this time because the mixed Walsh code is (0).

Because the pilot PN code is thus contained in the received pilot channel signal, the CDMA base station signal receiver 24 requires the same pilot PN code and Walsh code (0) to receive. The CDMA base station signal receiver 24 can thus synchronize with the pilot channel signal from the CDMA base station 16a, despread, and get data.

FIG. 13A shows the CDMA base station signal receiver 24 synchronizing with the pilot channel signal.

As shown in FIG. 13A, the pilot channel signal contains a string of 15 consecutive zeroes (0), the last zero (0) (the position indicated by the vertical arrow in FIG. 13A) is used for synchronization, and data for synchronizing to this bit is contained in the pilot PN synchronization data 42a.

Signals synchronized this way are synchronized with a superframe every 80 ms as described in FIG. 11.

The pilot PN synchronization program 32 then determines if synchronization with the pilot channel signal of the CDMA base station 15a is completed in ST4. If synchronization is not finished, the CDMA base station signal receiver 24 determines in ST5 if all service area tables in the wristwatch 10 have been referenced (through one cycle), and if they have not been referenced, control goes to ST6.

The data for CDMA base stations 15a in Japan, the United States, China, and Canada, for example, is referenced in ST6, and the pilot channel is scanned in ST1 based on this data.

For example, if the wristwatch 10 is looking for a CDMA base station 15a in Japan but is actually in the United States, synchronization with the pilot channel is not possible in ST3. Data for the CDMA base stations 15a in the United States is then acquired in ST6, and the pilot channel is scanned in ST1 based on this data.

However, is synchronization with the pilot channel signal is not possible even though all service area tables in the wristwatch 10 have been referenced in ST6, control goes to ST7. To indicate for the user that the time has not been adjusted, the seconds hand in FIG. 1 is moved 3 seconds, for example, in ST7 to inform the user. Adjusting the time is then left to the user, and operation ends. The user of the wristwatch 10 can thus be informed that something is different from usual.

If synchronization with the pilot channel signal is completed in ST4, control goes to ST8 and the start timing generator 17b inputs the start timing to the divide-by-64 counter 17c.

In this case the start timing generator control program 33 in FIG. 5 operates to generate and input the start timing to the divide-by-64 counter 17c in FIG. 3.

This is shown and described more specifically in FIG. 13B. FIG. 13B schematically describes the relationship between the start timing and the operation of the divide-by-64 counter 17c.

As shown in the figure, the divide-by-64 counter in FIG. 13B outputs at the synchronization timing of the pilot channel signal in FIG. 13A as indicated by the vertical arrow in the figure, and the start timing signal is also input to the divide-by-64 counter 17c at the timing indicated by this vertical arrow.

In ST9 the divide-by-64 counter 17c starts operating and frequency dividing at the start timing input from the start timing generator 17b

In this case the divide-by-64 counter 17c operates according to the divide-by-64 counter control program 34 in FIG. 5, divides the pilot PN chip rate frequency data 43a (1.2288 MHz) stored in the pilot PN chip rate frequency data storage unit 43 in FIG. 6 by 64, and generates a code as shown in FIG. 13B.

The length of this code is 64 chips including a 0 signal for the first 32 chips and a 1 signal for the second 32 chips, and is thus the same as the Walsh code (32) for getting data from the sync channel message in FIG. 12.

FIG. 14 schematically describes the process whereby the divide-by-64 counter 17c divides the pilot PN chip rate of 1.2288 MHz and generates the Walsh code (32).

As shown in FIG. 14 the pilot PN chip rate of 1.2288 MHz can be expressed as a digital signal of 0s and 1s.

When this 1.2288 MHz signal is divided by 64 by the frequency division counter 17c, the result is the Walsh code (32) of which the 32 chips in the first half are 0s and the 32 chips in the second half are is as shown in FIG. 13.

In ST9, the pilot PN code is first mixed by the sync channel signal, that is, the signal received form the CDMA base station 16a, and the signal is despread using the Walsh code (32) generated by the divide-by-64 counter 17c at the synchronization timing that can be recognized from the beginning of the pilot PN code. The signal is then passed through the digital filter 17d and deinterleaving and decoding unit 17e and interpreted to get the sync channel message in FIG. 12.

As shown in FIG. 12 the sync channel message contains time information (including the SYS_TIME). The signal transmitted from the CDMA base station 16a described above is therefore an example of a prescribed signal containing time information, and the time information can be extracted using the Walsh code (32) from the signal transmitted from the CDMA base station 16a.

The divide-by-64 counter 17c in FIG. 3 is an example of a time information extraction signal supply unit that supplies only the time information extraction signal, that is, Walsh code (32).

In this embodiment of the invention as shown in FIG. 13A and FIG. 13B, the CDMA base station 16a transmits a pilot channel signal indicating the starting part of the sync channel signal (the part indicated by the vertical arrow in FIG. 13), which is a prescribed signal containing time information, with the sync channel signal, and the start timing generator 17b supplies the start timing, which is a start signal, referenced to the pilot channel signal to the divide-by-64 counter 17c.

The message length information at the beginning of the sync channel message is then acquired in ST10. More specifically, the message length information acquisition program 317 in FIG. 5 gets and stores the message length information at the beginning of the sync channel message data as the message length information 611a in the message length information storage unit 511 in FIG. 7.

This message length information 611a is an example of identification information identifying the length of the data in the sync channel message. This superframe is an example of frame information of a fixed length, and the last superframe is an example of the last frame information.

It is therefore possible by getting this message length information to receive to the end of the sync channel message data without receiving to the end of the last superframe, and the CDMA base station signal receiver 24 can therefore stop signal reception once the sync channel message data is received.

Control then goes to ST11, and the CDMA base station signal receiver 24 in FIG. 3 stops signal reception. More specifically, the receiver control program 35 in FIG. 5 operates and stops reception of radio signals from the CDMA base station 16a by the CDMA base station signal receiver 24. Radio signal reception thus stops at the time indicated as G and GG at the end of the data in the sync channel message at a point before the end of the last superframe in FIG. 11. The receiver control program 35 is an example of a prescribed signal reception stopping unit. The CDMA base station signal receiver 24 is an example of a reception unit.

Power consumption can therefore be reduced when acquiring a prescribed signal containing time information because the reception unit stops immediately at the end of the prescribed signal.

Whether receiving the sync channel message is completed is then determined in ST12. If sync channel message reception is not completed, whether reception timed out is determined in ST13. If reception timed out, the sync channel message is received again in ST8.

This embodiment of the invention can thus generate the Walsh code (32) that is required to extract the sync channel message from the sync channel signal transmitted from the CDMA base station 16a by means of the divide-by-64 counter 17c, and does not require a Walsh code generator to generate the 64 types of Walsh codes as is required by the related art.

The circuit synchronize can therefore be reduced and power consumption can be reduced.

More specifically, the divide-by-64 counter in this embodiment of the invention can generate the Walsh code (32) as shown in FIG. 13B and FIG. 14 by simply frequency dividing the reference frequency of 1.2288 MHz, which is the pilot PN chip rate. The invention can therefore be realized using an extremely simple circuit arrangement and power consumption in particular can be reduced.

In addition, because frequency dividing by the divide-by-64 counter 17c is based on the start timing signal from the start timing generator 17b, which is referenced to the pilot PN signal synchronization timing, the sync channel message can be reliably extracted from the sync channel signal.

If reception of the sync channel message is determined in ST12 to have finished, the wristwatch 10 has received the entire sync channel message shown in FIG. 12, and this sync channel message is stored as the sync channel message data 61a in the sync channel message data storage unit 51 in FIG. 7.

Control then goes to ST14. In ST14 the message length offset time is extracted from the message length information 611a in the message length information storage unit 511 in FIG. 7. More specifically, the message length offset time data acquisition program 318 in FIG. 5 extracts the message length offset time corresponding to the message length information 611a in FIG. 7 from the message length offset time correlation data 411a in the message length offset time correlation data storage unit 411 in FIG. 6, and saves the extracted time as the message length offset time data 512a in the message length offset time data storage unit 512 in FIG. 7.

As shown in FIG. 15, the message length offset time correlation data 411a is stored to correlate the message length information with the corresponding message length offset time.

This message length offset time correlation data 411a is an example of a basic conversion time data table as basic conversion time data.

The message length offset time data acquisition program 318 is an example of an identified time difference information conversion unit. The message length offset time data 512a is an example of identified time difference information.

By thus storing a basic conversion time data table, the identified time difference information conversion unit can quickly extract and convert the identified time difference information from the basic conversion time data table once the identification information is acquired. Furthermore, because plural identification information and identified time difference information values are compiled in a table, the identified time difference information can be quickly extracted and converted for the identification information.

Alternatively, the message length offset time data acquisition program 318 can assign message length information 611a to each superframe and save the amount of data from the end of the sync channel message to the end of the last superframe, that is, the message length offset data times the time of 1 bit (0.833 ms), as the message length offset time data in the message length offset time data storage unit 512 in FIG. 7. In this case the basic conversion time is the product of the time of 1 bit (0.833 ms) times the message length offset data allocated to each superframe. This message length offset data is the part padded with 0s as described above.

Because the basic conversion time data is obtained in this case by allocating the data unit time for the identification information, the basic conversion time data can be quickly calculated and converted to the identified time difference information once the identification information is acquired, the identified time difference information can be calculated for the specific identification information, and the time can be adjusted.

Control then goes to ST15. From ST11 is the process for producing the time adjustment data and actually adjusting the time based on information in the sync channel message already acquired from the CDMA base station 16a.

The data for adjusting the time is produced using the leap seconds data shown in FIG. 12 in the sync channel message. The leap seconds data in FIG. 12 is therefore assumed to be correct. However, the leap seconds data in the sync channel message in FIG. 12 is often not accurate.

More specifically, the GPS time (SYS_TIME) is a time value that does not consider the Earth's rotation, the time must therefore be corrected to get the actual time on Earth, and this adjustment data is the leap seconds value. However, this leap seconds data is typically not accurately changed at the CDMA base station 16a when the data is implemented, such as at 0:00 or 9:00 a.m. on January 1, and the CDMA base station 16a data is usually changed sometime before, such as approximately a maximum six months in advance.

If the leap seconds value that is to be applied from 0:00 on January 1 of the next year is “14 seconds,” for example, and the leap seconds value used until then is “13 seconds,” the new leap seconds value of “14 seconds” is already changed in the sync channel data in July of the previous year.

As a result, the time will be 1 second late until 0:00 on January 1 of the next year, and the time cannot be accurately adjusted.

The following process is therefore executed.

First, in ST16, the GPS time SYS_TIME and the leap seconds LP_SEC, such as “14” seconds, are first acquired from the received sync channel message (sync channel message 61a in FIG. 7), and the UTC time (Universal Time Code) is calculated.

The UTC is the year, month, day, hour, minute, and second of Greenwich Mean Time.

More specifically, the UTC time calculation program 312 in FIG. 5 operates and the UTC is calculated based on the GPS time and the leap seconds value.

The calculated UTC time is then stored as the UTC time data 57a in FIG. 7 to the UTC time data storage unit 57.

Whether the leap seconds data that was received differs from the registered leap seconds data is then determined in ST17.

More specifically, a registered received leap seconds data storage unit 59 that stores the registered received leap seconds data 59a is provided in the second data storage unit 50 as shown in FIG. 7 for remembering the leap seconds value of the sync channel message (see FIG. 12) that was previously received from the CDMA base station 16a.

The leap seconds comparison program 314 in FIG. 5 then compares the leap seconds value in the sync channel message that was just received in ST9 above with the registered received leap seconds data 59a, and determines if the values are the same.

For example, the registered received leap seconds data of 13 seconds was received on August 20, and 14 seconds is received as the current leap seconds data on August 30, the registered received leap seconds data and the currently received leap seconds data are different.

In this case the “14 second” value is known to be the leap seconds value that should be used, for example, from 0:00 of January 1 of the next year.

The registered received leap seconds data storage unit 59 and the sync channel message data storage unit 51 are thus an example of a leap seconds information storage unit. The leap seconds comparison program 314 is an example of a leap seconds change determination unit.

If the leap seconds data is determined to be different in ST17, the leap seconds data that was received has changed and is the value for the next year, for example. Whether this leap seconds data should be used or not is then determined in ST18.

Whether the UTC time data 57a indicates 23:59:59 on June 30 or December 31 is then determined in ST18.

More specifically, whether the time has come when the currently received leap seconds data that was received in ST9 should actually be used (applied) is determined.

More specifically, the leap seconds correction determination program 316 makes this decision based on the UTC time data 57a in FIG. 7 and the leap seconds correction time data 48a in FIG. 6. Data such as 23:59:59 on June 30 or December 31 is stored in the leap seconds correction time data 48a as the correction time used for evaluation.

The leap seconds correction time data storage unit 48 in FIG. 6 is an example of a leap seconds application time information storage unit.

If in ST18 the UTC time data 57a indicates the time when the received leap seconds value is to be used, the leap seconds data that was just received (such as “14 seconds” in this example) is stored as the registered received leap seconds data 59a (ST19), and control goes to ST20.

In ST20 the current-reception-based first local time data 52a in FIG. 7 is calculated by the first local time calculation program 36 in FIG. 5.

The current-reception-based first local time data 52a is described next.

Because the wristwatch 10 in this embodiment of the invention is in Japan, for example, the GPS time, the currently received leap seconds, local offset time (UTC+9 in the case of Japan), and daylight savings time adjustment (0 hours in this example because there is no daylight savings time in Japan) are extracted from the sync channel message data 51a in FIG. 7, and the current received first local time, the first Japan time in this example, is calculated.

More specifically, the UTC is calculated referenced to the GPS time and the current received leap seconds data, for example, and the local time is calculated by adding the local offset time to the UTC time. In this example 9 hours is added to the UTC time to get Japan time. Because daylight savings time is not used in Japan, there is no adjustment for daylight savings time. In countries such as the United States where daylight savings time is used, the corrected daylight savings time is set with extremely high precision.

The current-reception-based first local time data 52a thus calculated is then stored in the current-reception-based first local time data storage unit 52 in FIG. 7.

The current-reception-based first local time data 52a thus uses the leap seconds data that was changed by the CDMA base station 16a, but this leap seconds value is applied at the correct time so that the time information is highly precise.

If the currently received leap seconds data does not differ from the registered leap seconds data in ST17, that is, even when the leap seconds values are the same, the first local time is calculated in ST20.

Unlike when ST17 returns Yes, however, the currently received leap seconds data has not been changed by the CDMA base station 16a. In this case, therefore, the current-reception-based first local time data 52a is calculated in ST20 based on a leap seconds value that has not changed.

If ST18 returns No, that is, the UTC time data 57a is not the specified time on June 30 or December 31, the currently received leap seconds data has changed but is not the leap seconds data to be applied at the current time.

If the time is adjusted using the currently received leap seconds data in this case, the time will be fast by the amount that the leap seconds value has changed, that is, by 1 second in the above example, and the time cannot be adjusted accurately.

Therefore, if ST18 returns No, this embodiment of the invention goes to ST21. Step ST21 calculates the registered-reception-based first local time data 58a based on the registered received leap seconds data 59a in FIG. 7 instead of the currently received leap seconds data.

As a result, the leap seconds data that matches the period when it should be applied is used to produce the data for adjusting the time, and the time can be prevented from being fast or slow by one second as happens with the related art.

This embodiment of the invention thus calculates the current-reception-based first local time data or the registered-reception-based first local time data as the first Japan time, and this time is the basic time based on the GPS time and the leap seconds data that is applicable to when the time is being set.

The current-reception-based first local time data 52a that is calculated here is described next. The current-reception-based first local time data 52a is described with reference to FIG. 11.

When the wristwatch 10 receives the signal from the CDMA base station 15b in FIG. 11 and extracts the sync channel message, the received time (GPS time) is the time (the time at F in FIG. 11) four superframes (320 ms) after the end of the last superframe referenced to the time with a pilot PN offset of 0 chips (0 ms).

However, because the pilot PN offset of signals transmitted from the CDMA base station 15b in FIG. 11 is 64 chips (0.052 ms), the actual signal reception time differs by the same amount from the accurate GPS time. In other words, the actual time (EE) at the end of the last superframe transmitted from the CDMA base station 15b in FIG. 11 is the time of the GPS time acquired by the wristwatch 10 plus the pilot PN offset.

The timing when the time of the wristwatch 10 is adjusted is at the end of the sync channel message as described above. The time EE of the end of the last superframe is therefore the time plus the message length offset time data 512a, which is the identified time difference between the time GG at the end of the sync channel message and the time EE at the end of the last superframe.

The invention therefore executes the following process. That is, the first local time data 52a in FIG. 7 is corrected as follows in ST22. The time at F in FIG. 11 is adjusted to the time at E by subtracting 320 ms (4 superframes) from the current-reception-based first local time data 52a. The message length offset time 512a is than also subtracted to get the time G indicating the end of the sync channel message. Because the pilot PN offset of signals from the CDMA base station 15b is 0.052 ms, this offset is then added.

The timing of the time adjustment of the wristwatch 10, Japan time in this example, is therefore generated based on the correct GPS time at the end of reception (GG) of the sync channel message.

The second local time calculation program 37 in FIG. 5 does this calculation based on the current-reception-based first local time data 52a or the registered-reception-based first local time data 58a in FIG. 7 and the time difference data 44a and the pilot PN offset time data 45a in FIG. 6, and stores the result as the second local time data 53a to the second local time data storage unit 53 in FIG. 7.

An example of the time difference data 44a in FIG. 6 is the value of 320 ms (4 superframes) used above, and is stored in the time difference data storage unit 44.

An example of the pilot PN offset time data 45a is the value of 64 chips (0.052 ms) used above, and is stored in the pilot PN offset time data storage unit 45.

The GPS time acquired from the sync channel message in ST9 is an example of the future time information at a prescribed time after (such as 320 ms after) the reception time information (such as the time at E in FIG. 11), which is the time when the reception unit (such as the CDMA base station signal receiver 24) receives.

The time difference data 44a in FIG. 6 is an example of time difference information.

The first local time calculation program 36 and the second local time calculation program 37 are an example of the reception time information generating unit that generates the reception time information of the reception unit (such as the second local time data 53a) based on the future time information (such as the time at F in FIG. 11) received by the reception unit (such as the CDMA base station signal receiver 24) and the time difference information (such as the time difference data 44a).

The second local time data 53a calculated in ST22 is a highly precise time matching the GPS time, but because time is required for the calculations done in ST20 or ST21 and ST22, the time differs (is inaccurate) from the precise GPS time by an amount equal to this calculation time.

ST23 is executed to compensate for this calculation time. More specifically, a process delay time is added to the second local time data 53a in FIG. 7 to calculate the final local time. More specifically, this process delay time is equal to the time required for these calculations by the wristwatch 10, and this time is therefore determined by the wristwatch 10.

In this embodiment of the invention the process delay time data 46a is therefore stored in the process delay time data storage unit 46 as a constant value as shown in FIG. 6. The final local time calculation program 38 in FIG. 5 then adds the process delay time data 46a to the second local time data 53a in FIG. 7, and stores the result as the final local time data 54a, which is a more precise time, in the final local time data storage unit 54.

The resulting final local time data 54a is highly precise time information reflecting the GPS time and the leap seconds value.

Control then goes to ST24. In ST24 the RTC and time adjustment program 39 in FIG. 5 adjusts the RTC 25 in FIG. 4 and the hands 13 in FIG. 1 based on the final local time data 54a in FIG. 7, and completes the time adjustment.

This embodiment of the invention can more accurately adjust the time because the leap seconds data acquired from the CDMA base station 16a is used accurately according to the period when the leap seconds data should be applied.

The RTC and time adjustment program 39 is thus an example of a display time information adjustment unit that adjusts the display time information of the time information display unit (such as the RTC 25 and the hands 13). The final local time calculation program 38 is an example of an adjustment time information generating unit that generates the adjustment time information (such as the final local time data 54a) used for adjustment by the RTC and time adjustment program 39.

As described above the RTC and time adjustment program 39 is an arrangement for adjusting the RTC 25, for example, based on the leap seconds information (such as the currently received leap seconds data) and the leap seconds application time information (including leap seconds correction time data 48a).

The RTC and time adjustment program 39 is also an arrangement for adjusting the RTC 25, for example, based on the leap seconds correction time data 48a and the leap seconds data which the leap seconds comparison program 314 determines if it has changed.

This embodiment of the invention can reduce power consumption from the battery 27 because the CDMA base station signal receiver 24 stops reception of signals from the CDMA base station 16a in ST11.

This is described more specifically with reference to FIG. 11. In FIG. 11 (C) denotes the power sequence of the related art when receiving the sync channel message from the CDMA base station 15b and then synchronizing the time. As shown in FIG. 11 the power remains on until FF in FIG. 11 because signals are being received.

This compares with the power sequence of this embodiment of the invention denoted by (D) in FIG. 11. As shown by (D) signal reception ends at GG in FIG. 11 and communication does not continue thereafter.

Because the wristwatch 10 according to this embodiment of the invention can reduce power consumption, the invention can be used in devices such as timepieces that require very little power while also enabling adjusting the time with extremely high precision.

Control then goes to ST25. A time adjustment interval timer operates in ST25. More specifically, the start time adjustment decision program 311 in FIG. 5 operates and references the time adjustment interval data 47a in FIG. 6. This time adjustment interval data 47a is 24 hours in this embodiment. The time adjustment interval data 47a is stored in the time adjustment interval data storage unit 47.

As a result, the next time adjustment process starts 24 hours after the previous time adjustment in ST25, and the process repeats from ST1.

FIG. 8 to FIG. 10 describe a process whereby the local offset time and the daylight savings time data in FIG. 12 are automatically adjusted based on the sync channel message received from the CDMA base station 15a, but this data can alternatively be set by the user of the wristwatch 10.

In this case the local offset time that is input using the crown 28 in FIG. 1, for example, is stored as the input local offset time data 55a in FIG. 7 to the input local offset time data storage unit 55. The similarly input daylight savings time data is stored as the input daylight savings time data 56a in the input daylight savings time data storage unit 56.

The current-reception-based first local time data 52a, for example, is calculated based on this input data in ST20 or ST21 described above, and the time can therefore be adjusted as desired by the user.

This embodiment is described using by way of example adding “1 second” as the leap seconds in the CDMA base station 15a, but the invention is not so limited and includes arrangements in which “1 second” is subtracted.

Furthermore, Walsh code (32) is generated by the divide-by-64 counter 17c, for example, in the above embodiment, but the invention is not so limited. Alternatively, in FIG. 6 a code signal for the Walsh code (32) shown in FIG. 13B and FIG. 14 can be stored and mixed with the sync channel signal by the baseband unit 17 in FIG. 3.

This arrangement enables reducing the circuit size even more, and reduces the power consumption.

The storage unit for the Walsh code (32) in this variation is a time information extraction signal storage unit.

The invention is not limited to the foregoing embodiment. Whether to apply the leap seconds value is determined above referenced to 23:59:59 on June 30 or December 31, but the invention is not so limited and a reference time of 00:00:00 on July 1 or January 1, or 00:00:30 on July 1 or January 1, can be used.

This arrangement is effective when the CDMA base station 16a inserts (changes) the leap seconds value at 23:59:59 on June 30 or December 31 or later.

The invention being thus described, it will be obvious that it may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

Time Adjustment Device, Timepiece with a Time Adjustment Device, and Time Adjustment Method

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