Patent Publication Number: US-10317847-B2

Title: Electronic timepiece

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to an electronic timepiece. 
     2. Related Art 
     For example, various technologies for sharing driving devices that rotate indicators such as second hands or minute hands have been proposed between a plurality of types of electronic timepieces with different specifications in the related art. For example, JP-A-2014-102112 discloses a configuration in which one of a plurality of driving pulses generated at different periods is selected according to data designating the specification of a device. In a technology of JP-A-2014-102112, a specification corresponding to a reduction in power voltage is selected in a case in which the power voltage is reduced up to a power voltage less than a predetermined value. 
     Incidentally, for example, data designating a specification of an electronic timepiece is abruptly changed to content different from appropriate content corresponding to an actual specification, for example, due to chattering of a power voltage caused by an impact at the time of falling of an electronic timepiece or an instantaneous variation in a voltage caused by static electricity. Accordingly, an operation appropriate for an electronic timepiece is hindered. As a result, there is a possibility of a user feeling a sense of discomfort. 
     SUMMARY 
     An advantage of some aspects of the invention is to provide a technology for quickly correcting content appropriate for specification data changed abruptly. 
     An electronic timepiece according to a preferred aspect of the invention includes: a latch unit that latches and outputs specification data designating a specification in accordance with a latch signal; a signal output unit that outputs one of a plurality of driving signals including driving pulses at different periods based on the specification data output from the latch unit; a driving unit that drives a motor based on the driving signal output from the signal output unit; and a control unit that generates the latch signal so that the latch signal has at least an active level at a timing before generation of each driving pulse of the driving signal with a shortest period of the driving pulse among the plurality of driving signals. In the aspect of the invention, the latch signal is generated so that the latch signal has at least the active level at the timing before generation of each driving pulse of the driving signal with the shortest period of the driving pulse among the plurality of driving signals. Accordingly, when the specification data output from the latch unit abruptly varies, it is possible to quickly correct the specification data to appropriate content. 
     The electronic timepiece according to the preferred aspect of the invention may further include a storage unit that stores the specification data. The latch unit may latch the specification data read from the storage unit. The electronic timepiece according to another aspect of the invention may further include a setting terminal with which one of a plurality of voltages is supplied. The latch unit may latch and output the specification data according to the voltage of the setting terminal in accordance with the latch signal. 
     In the preferred aspect of the invention, the driving pulse may include a plurality of sub-pulses. The control unit may set the latch signal to the active level during a period of the sub-pulses occurring in succession. In the foregoing aspect of the invention, the latch signal is set to the active level during the period of the sub-pulses included in the driving pulse. That is, the latch unit latches the specification data within the period of the driving pulse. Accordingly, even in a case in which the specification data output from the latch unit abruptly varies within the period of the driving pulses, the specification data can quickly be corrected without waiting for an immediately subsequent driving pulse. 
     In the preferred aspect of the invention, the control unit may generate the latch signal so that the latch signal has the active level at the timing before the generation of the driving pulses of each of the plurality of driving signals. In the foregoing aspect of the invention, the latch signal is generated so that the latch signal has the active level at the timing before the generation of the driving pulses of each of the plurality of driving signals. Accordingly, the above-described advantage of quickly correcting the specification data output by the latch unit is particularly noticeable. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIG. 1  is a diagram illustrating the configuration of an electronic timepiece according to a first embodiment of the invention. 
         FIG. 2  is a diagram illustrating waveforms of signals used in the electronic timepiece. 
         FIG. 3  is a diagram illustrating a problem of a comparative example. 
         FIG. 4  is a diagram illustrating advantages according to a first embodiment. 
         FIG. 5  is a diagram illustrating the configuration of an electronic timepiece according to a second embodiment. 
         FIG. 6  is a diagram illustrating waveforms of signals used in the electronic timepiece according to the second embodiment. 
         FIG. 7  is a diagram illustrating the waveforms of a driving pulse and a latch signal according to a third embodiment. 
         FIG. 8  is a diagram illustrating waveforms of signals used in an electronic timepiece according to a fourth embodiment. 
         FIG. 9  is a diagram illustrating waveforms of signals used in an electronic timepiece according to a modification example. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     First Embodiment 
       FIG. 1  is a diagram illustrating an example of the configuration of an electronic timepiece  100  according to a first embodiment of the invention. As exemplified in  FIG. 1 , the electronic timepiece  100  according to the first embodiment is an electronic device that includes a driving device  12 , a motor  14 , an indicator  16 , and a power unit  18 . A wristwatch mounted on a wrist of a user is a typical example of the electronic timepiece  100  and any specific form of the electronic timepiece  100  is used. 
     The indicator  16  is a second hand or a minute hand used to indicate a time. The motor  14  rotates the indicator  16 . The motor  14  according to the first embodiment is a stepping motor including a coil  142  and a rotor  144 . When a driving pulse O 1  and a driving pulse O 2  are supplied to the coil  142 , the rotor  144  is rotated. Then, the rotation of the rotor  144  is transmitted to the indicator  16  via a wheel structure (not illustrated) including gears to rotate the indicator  16 . The power unit  18  is configured to include, for example, a battery and supplies a power voltage VDD and a ground voltage VSS to the driving device  12 . 
     The driving device  12  is an electronic circuit that drives the motor  14  when power is fed from the power unit  18 . For example, the driving device  12  is mounted in the form of, for example, an integrated circuit (IC) chip on the electronic timepiece  100 . The driving device  12  according to the first embodiment can be used in a plurality of kinds of electronic timepieces  100  with different specifications. As exemplified in  FIG. 1 , the driving device  12  according to the first embodiment includes an oscillation circuit  22 , a control unit  24 , a storage unit  26 , a latch unit  28 , a signal output unit  30 , and a driving unit  32 . The elements of the driving device  12  can also be distributed into a plurality of IC chips. 
     The oscillation circuit  22  generates an oscillation signal with a predetermined frequency using an oscillation source  220  such as a crystal oscillator. The control unit  24  is configured to include a divider circuit that divides the oscillation signal generated by the oscillation circuit  22  and generates various signals (for example, a read signal R, a latch signal L, and a criterion signal C) that define a timing of an operation of each component of the driving device  12 . 
     The storage unit  26  is a nonvolatile memory configured with, for example, a semiconductor memory. The storage unit  26  according to the first embodiment stores data D designating the specification of the electronic timepiece  100  on which the driving device  12  is mounted (hereinafter referred to as “specification data”). For example, the specification data D with content according to the specification of the electronic timepiece  100  is stored in the storage unit  26  before shipment of the electronic timepiece  100 . The storage unit  26  according to the first embodiment outputs the specification data D according to the read signal R generated by the control unit  24 . 
     The latch unit  28  latches the specification data D retained in the storage unit  26  and outputs the specification data D to the signal output unit  30 . Specifically, the latch unit  28  imports the specification data D from the storage unit  26  at a timing defined by the latch signal L generated by the control unit  24  and retains an output of the specification data D to the signal output unit  30 . 
     The signal output unit  30  includes a signal generation unit  42 , a signal generation unit  44 , and a selection unit  46 . The criterion signal C generated by the control unit  24  is supplied to the signal generation units  42  and  44 . The criterion signal C is a clock signal with a predetermined period. The signal generation unit  42  generates a driving signal XA based on the criterion signal C. The signal generation unit  44  generates a driving signal XB based on the criterion signal C. The driving signal XA includes driving signals XA 1  and XA 2 . The driving signal XB includes driving signals XB 1  and XB 2 . 
       FIG. 2  is a diagram illustrating waveforms of signals used in the electronic timepiece  100 . As exemplified in  FIG. 2 , the driving signals XA 1 , XA 2 , XB 1 , and XB 2  each include a driving pulse PX. The driving pulse PX is a pulse used for the driving unit  32  to drive the motor  14 . In the first embodiment, the driving pulse PX with a waveform in which a plurality of sub-pulses are arranged in a pectinate shape at intervals is exemplified. A detection pulse PD is set immediately after the driving pulse PX. The detection pulse PD has a pulse waveform with a pectinate shape as in the driving pulse PX and is used to detect rotation of the rotor  144 . The detection of rotation of the detection pulse PD is disclosed in JP-A-2003-333896 or JP-A-2013-255393. 
     As exemplified in  FIG. 2 , the plurality of driving pulses PX are set at a period  2 TA in each of the driving signals XA 1  and XA 2 . A position of the driving pulse PX on the time axis differs between the driving signals XA 1  and XA 2 . That is, in the driving signals XA including the driving signals XA 1  and XA 2 , the driving pulse PX is set at the period TA. On the other hand, in each of the driving signals XB 1  and XB 2 , the plurality of driving pulses PX are set at a period  2 TB. A position of the driving pulse PX on the time axis differs between the driving signals XB 1  and XB 2 . That is, in the driving signals XB including the driving signals XB 1  and XB 2 , the plurality of driving pulses PX are set at a period TB. As understood from  FIG. 2 , the period TB is longer than the period TA. Specifically, the period TB is set at an integer multiple of the period TA. For example, the period TA is set to 1 second and the period TB is set to 20 seconds. 
     The selection unit  46  in  FIG. 1  selectively outputs one of the driving signals XA (XA 1  and XA 2 ) generated by the signal generation unit  42  and the driving signals XB (XB 1  and XB 2 ) generated by the signal generation unit  44  according to the specification data D output from the latch unit  28 . The specification data D according to the first embodiment designates a first specification for driving the indicator  16  (for example, a second hand) at the period TA and a second specification for driving the indicator  16  (for example, a minute hand) at the period TB. In the electronic timepiece  100  in which the specification data D designates the first specification, the selection unit  46  selects the driving signal XA in which the driving pulse PX is set at the period TA as the driving signals X (X 1  and X 2 ). On the other hand, in the electronic timepiece  100  in which the specification data D designates the second specification, the selection unit  46  selects the driving signal XB in which the driving pulse PX is set at the period TB as the driving signals X (X 1  and X 2 ). As exemplified in  FIG. 2 , a high level of the specification data D means the first specification and a low level of the specification data D means the second specification. In  FIG. 2 , a case in which the first specification for driving the indicator  16  at the period TA is designated by the specification data D is exemplified for convenience. 
     The driving signal X selected by the selection unit  46  is supplied to the driving unit  32 . Specifically, one of a pair of driving signals XA 1  and XA 2  and a pair of driving signals XB 1  and XB 2  is supplied as the driving signals X 1  and X 2  to the driving unit  32 . As understood from the foregoing description, the signal output unit  30  according to the first embodiment functions as an element that outputs one of the plurality of driving signals (the driving signal XA with the period TA and the driving signal XB with the period TB) in which the periods of the driving pulses PX are different. 
     The driving unit  32  drives the motor  14  based on the driving signal X output from the signal output unit  30 . Specifically, the driving unit  32  supplies the coil  142  of the motor  14  with the driving pulse O 1  according to each driving pulse PX of the driving signal X 1  and the driving pulse O 2  according to each driving pulse PX of the driving signal X 2 . In the electronic timepiece  100  in which the specification data D designates the first specification, as exemplified in  FIG. 2 , the driving pulse O 1  and the driving pulse O 2  are alternately supplied to the coil  142  at each period TA (for example, 1 second). Accordingly, the indicator  16  (for example, a second hand) is driven sequentially at the period TA. On the other hand, in the electronic timepiece  100  in which the specification data D designates the second specification, the driving pulse O 1  and the driving pulse O 2  are alternately supplied to the coil  142  at each period TB (for example, 20 seconds). 
     As exemplified in  FIG. 2 , the control unit  24  sets the read signal R and the latch signal L at an active level (a high level in the example of  FIG. 2 ) immediately after power is fed to the electronic timepiece  100  (time point t 0 ). Through the foregoing operation, the specification data D is output from the storage unit  26  and the specification data D is latched by the latch unit  28 . That is, whether the driving signal XA or the driving signal XB is output to the driving unit  32  is decided according to the specification data D immediately after power is fed to the electronic timepiece  100 . 
     Further, the control unit  24  according to the first embodiment controls the storage unit  26  and the latch unit  28  such that the specification data D is output by the storage unit  26  and the specification data D is latched by the latch unit  28  at a timing before generation of each driving pulse PX of the driving signal XA. Specifically, as exemplified in  FIG. 2 , the control unit  24  sets the read signal R and the latch signal L to an active level at a timing before the generation of each of the plurality of driving pulses PX of the driving signal XA. That is, the read signal R and the latch signal L are set to the active level sequentially at the same period TA as the driving signal XA. As understood from the foregoing operation, in the first embodiment, the latch of the specification data D by the latch unit  28  is repeated periodically not only immediately after feeding of power but also in a subsequent normal operation state. 
     Incidentally, the power voltage VDD instantaneously varies (chatters) due to disturbance such as an impact at the time of falling of the electronic timepiece  100  or static electricity in some cases. When the instantaneous variation of the power voltage VDD occurs, there is a possibility of content of the specification data D output from the latch unit  28  to the signal output unit  30  being abruptly changed. In the first embodiment, since the latch of the specification data D is repeated a plurality of times by the latch unit  28 , the specification data D abruptly varying due to the variation in the power voltage VDD can quickly be corrected to appropriate content, as will be described in detail below. 
       FIG. 3  is a diagram illustrating an operation in a configuration (hereinafter referred to as a “comparative example”) in which a latch unit  28  latches specification data D only immediately after power is fed (time point t 0 ). In  FIG. 3 , a case in which the specification data D designates the first specification (a case in which the specification data D is set to a high level) is assumed as in  FIG. 2 . 
     As exemplified in  FIG. 3 , when an instantaneous variation in the power voltage VDD occurs, the level of the specification data D output from the latch unit  28  to the signal output unit  30  can be reversed from a high level corresponding to the first specification to a low level meaning the second specification at time point t 1 . Accordingly, the driving signal XB in which the driving pulse PX is set at the period TB transitions to a state output from the signal output unit  30  to the driving unit  32 . As a result, the indicator  16  is driven at the period TB. In the above state, the driving pulses (O 1  and O 2 ) which are normally output to the motor  14  are not output in a section E of  FIG. 3 . That is, an appropriate operation of rotating the indicator  16  at the period TA is hindered, and thus there is a possibility of a user feeling a sense of discomfort. 
       FIG. 4  is a diagram illustrating an operation in a case in which a power voltage VDD abruptly varies in the configuration according to the first embodiment. As exemplified in  FIG. 4 , even in the first embodiment, the level of the specification data D to be output to the signal output unit  30  is reversed from the high level corresponding to the original specification to the low level at time point t 1 . In the first embodiment, however, immediately after time point t 1  of the variation in the power voltage VDD, the latch signal L is set to the active level at time point t 2  before generation of each driving pulse PX of the driving signal XA. Accordingly, the specification data D retained in the storage unit  26  is latched again, and thus the level of the specification data D to be output to the signal output unit  30  is corrected to the high level corresponding to the original specification of the electronic timepiece  100 . That is, according to the first embodiment, it is possible to quickly correct the specification data D abruptly varying due to the variation in the power voltage VDD to the appropriate content, compared to the comparative example of  FIG. 3 . In the first embodiment, particularly, the latch signal L is set to the active level before generation of each driving pulse PX of the driving signal XA with a short period between the driving signals XA and XB. Accordingly, the above-described advantage of quickly correcting the abruptly varying specification data D is particularly noticeable, compared to the configuration in which the latch signal L is set to the active level before generation of each driving pulse PX of the driving signal XB. 
     Second Embodiment 
     A second embodiment of the invention will be described. Reference numerals used to describe the first embodiment are given to the same elements as those of the first embodiment in operational effects and functions in each aspect to be exemplified below, and the detailed description thereof will be appropriately omitted. 
       FIG. 5  is a diagram illustrating an example of the configuration of an electronic timepiece  100  according to the second embodiment. As exemplified in  FIG. 5 , the electronic timepiece  100  according to the second embodiment is configured such that the storage unit  26  of the first embodiment is substituted with a pull-down circuit  34  in  FIG. 5 . The pull-down circuit  34  is a circuit that outputs the specification data D according to a voltage of a setting terminal  36  and includes a switch  342  that is disposed between the setting terminal  36  and a ground wire (ground voltage VSS) and controls electric connection between the setting terminal  36  and the ground wire. The switch  342  is configured with, for example, an n-channel type transistor and is set to either an on state or an off state according to a control signal Q supplied from the control unit  24 . 
     The setting terminal  36  is a terminal that designates a specification of the electronic timepiece  100 . For example, a bonding option terminal of an IC chip is appropriately used as the setting terminal  36 . A voltage state of the setting terminal  36  is selected according to the specification of the electronic timepiece  100 . Specifically, the setting terminal  36  is set to the power voltage VDD in the electronic timepiece  100  of the first specification in which the indicator  16  is driven at the period TA. The setting terminal  36  is set to an open state in the electronic timepiece  100  of the second specification in which the indicator  16  is driven at the period TB. 
       FIG. 6  is a diagram illustrating waveforms of signals used in the electronic timepiece  100  according to the second embodiment. As exemplified in  FIG. 6 , the control signal Q of the second embodiment has the same waveform as the read signal R of the first embodiment. That is, the control signal Q and the latch signal L are set to the active level at a timing immediately after feeding (time point t 0 ) of power of the electronic timepiece  100  and a timing before generation of each driving pulse PX of the driving signal XA. 
     When the control signal Q is set to the active level, the specification data D according to a voltage of the setting terminal  36  is supplied to the latch unit  28 . Specifically, in the first specification in which the setting terminal  36  is set to the power voltage VDD, the power voltage VDD is supplied as the specification data D to the latch unit  28 . On the other hand, in the second specification in which the setting terminal  36  is set to the open state, the setting terminal  36  is set to the ground voltage VSS when the switch  342  transitions to the on state in accordance with the control signal Q. Accordingly, the ground voltage VSS is supplied as the specification data D to the latch unit  28 . An operation in which the latch unit  28  latches the specification data D according to the latch signal L or operations of the signal output unit  30  and the driving unit  32  are the same as those of the first embodiment. In the second embodiment, the same advantages as those of the first embodiment are realized. 
     Third Embodiment 
       FIG. 7  is a diagram illustrating a relation between the latch signal L and the driving pulse PX according to a third embodiment. As exemplified in  FIG. 7 , driving pulses PX of driving signals (XA 1 , XA 2 , XB 1 , XB 2 ) include a plurality of (five in the example of  FIG. 7 ) sub-pulses pS. The latch signal L of the first embodiment is set to the active level before generation of the driving pulse PX and even during a period of the driving pulse PX. Specifically, the control unit  24  sets the latch signal L to the active level during each period δ between the sub-pulses pS occurring in succession. Accordingly, the specification data D output from the storage unit  26  is latched by the latch unit  28  even during each period δ between the sub-pulses pS besides before the generation of the driving pulse PX. 
     Even in the third embodiment, the same advantages as those of the first embodiment are realized. Incidentally, in the first and second embodiments, the specification data D may not be corrected up to before the generation of the immediately subsequent driving pulse PX in a case in which the specification data D output from the latch unit  28  to the signal output unit  30  abruptly varies at a time point during the course of the driving pulse PX. In contrast, in the third embodiment, the latch signal L is set to the active level within a period of the driving pulse PX. Accordingly, there is the advantage of quickly correcting the specification data D without waiting for the immediately subsequent driving pulse PX in a case in which the specification data D output from the latch unit  28  abruptly varies within the period of the driving pulse PX. 
     Fourth Embodiment 
       FIG. 8  is a diagram illustrating waveforms of signals used in an electronic timepiece  100  according to a fourth embodiment. As exemplified in  FIG. 8 , in the fourth embodiment, the positions of the driving pulses PX are selected so that the driving pulses PX of the driving signals XA (XA 1  and XA 2 ) and the driving pulses PX of the driving signals XB (XB 1  and XB 2 ) do not overlap on the time axis. Specifically, the driving pulse PX of the driving signal XB occurs at a time point at which a time the driving pulse PX delays by a time τ with respect to the driving pulse PX of the driving signal XA. 
     As exemplified in  FIG. 8 , the control unit  24  according to the fourth embodiment generates the latch signal L and the read signal R (the control signal Q according to the second embodiment) so that the latch signal L and the read signal R have the active level at timings before generation of the driving pulses PX of the driving signals XA and XB. That is, the latch signal L and the read signal R are set to the active level at both timings before generation of the driving pulses PX of the driving signals XA 1  and XA 2  and timings before generation of the driving pulses PX of the driving signals XB 1  and XB 2 . 
     Specifically, as exemplified in  FIG. 8 , the latch signal L is generated by logical sum of the latch signal LA having the active level before the generation of each driving pulse PX of the driving signal XA and the latch signal LB having the active level before the generation of each driving pulse PX of the driving signal XB. Similarly, the read signal R is generated by logical sum of the read signal RA having the active level before the generation of each driving pulse PX of the driving signal XA and the read signal RB having the active level before the generation of each driving pulse PX of the driving signal XB. As understood from the foregoing description, the specification data D is latched by the latch unit  28  before the generation of each driving pulse PX of both the driving signals XA and XB. 
     In the fourth embodiment, the same advantages as those of the first embodiment are realized. In the fourth embodiment, the latch signal L is set to the active level at the timings before the generation of the driving pulses PX of the driving signals XA and XB. That is, the abruptly varying specification data D is corrected immediately before the generation of the driving pulse PX. Accordingly, the above-described advantage of quickly correcting the specification data D abruptly varying due to the variation in the power voltage VDD is particularly noticeable. 
     In configuration for supplying the specification data D to the latch unit  28  in the third and fourth embodiments, either the configuration of the first embodiment in which the storage unit  26  is used or the configuration of the second embodiment in which the pull-down circuit  34  is used can be adopted. 
     Modification Examples 
     The above-described embodiments can be modified in various forms. Specific modification forms will be exemplified below. Two or more forms arbitrarily selected from the following examples can be appropriately merged within the scope of the invention in which the forms are not mutually contradicted. 
     (1) In the above-described embodiments, the driving pulses PX with the pectinate shape in which the plurality of sub-pulses pS are arranged have been exemplified, but the waveform of the driving pulse PX is not limited to the foregoing example. For example, as exemplified in  FIG. 9 , the driving pulse PX with a single rectangular wave can also be used. 
     (2) In the above-described embodiments, the configuration in which two kinds of driving signals XA and XB are selected according to the specification data D has been exemplified, but the number of kinds of signals which are candidates selected according to the specification data D is not limited to two kinds of signals. That is, any of three or more kinds of driving signals having different periods of the driving pulses PX can also be output according to the specification data D by the signal output unit  30 . From the viewpoint that the abruptly varying specification data D is quickly corrected, it is proper for the control unit  24  to generate the latch signal L so that the latch signal has at least the active level at a timing before the generation of each driving pulse PX of the driving signal (in the above-described, the driving signal XA) with the shortest period of the driving pulse PX among the plurality of driving signals. 
     (3) In the above-described embodiments, the configuration in which the selection unit  46  selects either the driving signal XA generated by the signal generation unit  42  or the driving signal XB generated by the signal generation unit  44  has been exemplified, but a configuration in which either the driving signal XA or the driving signal XB is selectively output is not limited to the above example. For example, it is possible that either the driving signal XA or the driving signal XB is selectively generated according to the specification data D. Specifically, in a case in which the specification data D designates the first specification, the driving signal XA is generated by the signal generation unit  42  whereas the generation of the driving signal XB by the signal generation unit  44  is stopped. On the other hand, in a case in which the specification data D designates the second specification, the generation of the driving signal XA by the signal generation unit  42  is stopped whereas the driving signal XB is generated by the signal generation unit  44 . In the foregoing configuration, the selection unit  46  is not necessary. As understood from the foregoing example, the signal output unit  30  in each of the above-described embodiments is inclusively expressed as an element to output one of the plurality of driving signals (XA and XB) based on the specification data D, and therefore the plurality of driving signals may be actually generated, and one driving signal may be selectively output or any of the plurality of driving signals may be selectively generated. 
     The entire disclosure of Japanese Patent Application No. 2016-057826, filed Mar. 23, 2016 is expressly incorporated by reference herein.