Abstract:
An electric timepiece is disclosed as including a micro-controlling with a volatile RAM adapted to be written with time-related data, an EEPROM or FRAM adapted to be written with time-related data, and a stepping motor operatively associated with an analog time display, in which the time-related data in the volatile RAM and in the EEPROM or FRAM are synchronized with each other, and the micro-controller is adapted to update the time-related data in the volatile RAM and in the EPPROM or FRAM simultaneously every second.

Description:
[0001]     This invention relates to an electronic timepiece with analog display, in particular, such a timepiece having a signal receiver for receiving externally transmitted time-related radio signals, and a method of operating such a timepiece.  
       BACKGROUND OF THE INVENTION  
       [0002]     U.S. Pat. No. 6,072,752 discloses a hand display-type electronic timepiece which allows a user to synchronize the hands and the timing counter. This is achieved by providing a power source voltage detecting means which monitors the voltage of the battery/electric cell at all times. A predetermined output signal is generated when the fact that the voltage of the battery has dropped below a predetermined level is detected by the power source voltage detecting means. The hand position data are written into a non-volatile memory in response to the above output signal, and the hands are stopped at the same time. When a new battery is replaced, and the timepiece resumes operation, the timepiece will obtain radio signals relating to the accurate current time from an outside source, compare it with the hand position data written into the non-volatile memory, and drive the hands to move so that the displayed time corresponds to, and is thus synchronized with, the current time.  
         [0003]     In some very common circumstances where the battery voltage is normal but, for some reason, the battery has to be removed from the timepiece, no predetermined output signal will be generated in accordance with the arrangement disclosed in U.S. Pat. No. 6,072,752 before removal of the battery. No hand position will then be written into the non-volatile memory, in which case the above feature cannot function.  
         [0004]     German Patent Document No. DE 195 07 543 A1 discloses a radio-controlled clock/watch with an analogue display which is enabled, by the use of a non-volatile memory with a buffer memory upstream, to return the hands, after interruptions of normal operating conditions, to the position corresponding to the broadcast signals of current time. As in the case of the electronic timepiece disclosed in U.S. Pat. No. 6,072,752, no hand position data will be written into the non-volatile memory if the interruption of operation is due to a sudden disconnection of power supply. In such a case, there is no power for the RAM to execute the backup operation, and the EEPROM will have no data to show the position of the hands before the interruption.  
         [0005]     It is thus an object of the present invention to provide an electronic timepiece and a method of operating an electronic timepiece in which the aforesaid shortcomings are mitigated, or at least to provide a useful alternative to the public.  
       SUMMARY OF THE INVENTION  
       [0006]     According to a first aspect of the present invention, there is provided an electric timepiece including a controlling device with at least a volatile memory adapted to be stored with time-related data, a non-volatile memory adapted to be stored with time-related data, and a motor operatively associated with an analog time display, wherein said time-related data in said volatile memory and in said non-volatile memory are synchronized with each other, and wherein said controlling device is adapted to update said time-related data in said volatile memory and in said non-volatile memory simultaneously every second.  
         [0007]     According to a second aspect of the present invention, there is provided a method of operating an electric timepiece including the steps of providing a controlling device with at least a volatile memory; providing a non-volatile memory; providing a motor operatively associated with an analog time display; writing time-related data into said volatile memory; writing time-related data into said non-volatile memory; synchronizing said time-related data in said volatile memory and in said non-volatile memory; and said controlling device updating said time-related data in said volatile memory and in said non-volatile memory simultaneously every second. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     Preferred embodiments of the present invention will now be described, by way of examples only, with reference to the accompanying drawings, in which:  
         [0009]      FIG. 1  shows a block diagram of a first embodiment of a timepiece according to the present invention;  
         [0010]      FIG. 2  shows a block diagram of a second embodiment of a timepiece according to the present invention;  
         [0011]      FIG. 3  shows a block diagram of a micro-controller (MCU) which may be used in a timepiece according to the present invention;  
         [0012]      FIG. 4  shows a block diagram of an EEPROM which may be used as a non-volatile memory in a timepiece according to the present invention; and  
         [0013]      FIG. 5  shows a block diagram of a FRAM which may also be used as a non-volatile memory in a timepiece according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0014]     A block diagram of an electronic timepiece according to a first embodiment of the present invention is shown in  FIG. 1 , and generally designated as  100 . The operation of the timepiece  100  is controlled by a micro-controller (MCU)  102  with a processor  104  and a volatile memory  106 , e.g. a volatile RAM. The MCU  102  is connected with a radio signal receiver  108 , which receives externally transmitted time-related radio signals giving the accurate current time, e.g. from a satellite. Both the processor  104  and the volatile RAM  106  of the MCU  102  are also connected with an external non-volatile memory  110 , e.g. an electrically erasable programmable read-only memory (EEPROM) or a ferroelectric random access memory (FRAM).  
         [0015]     The MCU  102  is connected with two switches  112  operable to input time-related instructions into the timepiece  100 , in lieu of time-related signals received from the external source. The MCU  102  sends pulse signals, through motor drive input/output (I/O) ports  114   a ,  114   b , to poles  118   a ,  118   b  of a stepping motor  116  to drive a mechanical time display for displaying the time in an analog manner. The MCU  102  also includes two pulse width measurement input/output (I/O) ports  120   a ,  120   b  for measuring the “width” of the pulse signals sent via the motor drive I/O ports  114   a ,  114   b  to the poles  118   a ,  118   b  of the stepping motor  116 .  
         [0016]     In the present application, mechanical time display or analog display refers to, but is not limited to, hour hand, minute hand, seconds hand, day hand, week hand, month hand, year hand, and various other kinds of mechanical display devices, e.g. panel displays at airports showing the flight arrival/departure time.  
         [0017]     A micro-controller which may be used in the present invention may be a 4K 4-Bit micro-controller with liquid crystal display (LCD) driver manufactured and traded by Novatek Microelectronics Corp. Ltd. of Taiwan under Model No. NT6613. A block diagram of this micro-controller is shown in  FIG. 3 . This is a single chip micro-controller integrated with static random access memory (SRAM), timer and dual-tone PSG, LCD driver and I/O port. Table 1 below gives the pad description of this micro-controller.  
                       TABLE 1                       Designation   I/O   Description                   SEG1-SEG 34   O   Segment signal output for LCD display;               Share with scans output.       V LCD , V 1 , V 2 , V 3     I   Connect with external LCD divided               resistance       TEST   I   Test pin (Internal pull-low). No connect for               user.       /RESET   I   Reset pin (No internal pull-up)       V DD     P   Power supply.       Port B.3-Port B.0   I/O   Bit programmable I/O, Vector interrupt               (/INT1)       Port A.3-Port A.0   I/O   Bit programmable I/O, PA.0 shared with               /INT0 PA.1, PA.2 shared with PSG output       OSCXI   I   Oscillator X input pin       OSCXO   O   Oscillator X output pin       GND   P   Ground pin       OSCO   O   Oscillator output pin       OSCI   I   Oscillator input pin       COM1-COM4   O   Common signal output for LCD display                  
 
         [0018]     A non-volatile memory which may be used in the present invention may be an 8K-bit EEPROM manufactured and traded by Samsung Electronics of Korea under Model No. S524C80D81. A block diagram of this EEPROM is shown in  FIG. 4 . Table 2 below gives the pad description of this EEPROM.  
                       TABLE 2                       Name   Type   Description                   A0, A1, A2   Input   Input pins for device address selection. To configure               a device address, these pins should be connected               to the V CC  or V SS  of the device.       V SS     —   Ground pin.       SDA   I/O   Bi-directional data pin for the I 2 C ™-bus serial data               interface. Schmitt trigger input and open-drain               output. An external pull-up resistor must be               connected to V CC . Typical values for this               pull-up resistor are 4.7 kΩ (100 kHz)               and 1 kΩ (400 kHz).       SCL   Input   Schmitt trigger input pin for serial clock input       WP   Input   Input pin for hardware write protection control. If               this pin is tied to V CC , the write function is               disabled to protect previously written data in the               entire memory. If this pin is tied to V SS , the write               function is enabled.       V CC     —   Single power supply.                  
 
         [0019]     Another non-volatile memory which may be used in the present invention may be a 4 Kb-FRAM serial 3V memory manufactured and traded by Ramtron International Corporation of Colorado Springs, USA under serial number FM25CL04. A FRAM is non-volatile and performs reads and writes like a RAM. A block diagram of this non-volatile memory is shown in  FIG. 5 . Table 3 below gives the pin description of this non-volatile memory.  
                       TABLE 3                       Pin Name   I/O   Description                   /CS   Input   Chip Select: This active low input activates the device.               When high, the device enters low-power standby mode,               ignore other inputs, and all outputs are tri-stated. When low,               the device internally activates the SCK signal. A falling edge               on /CS must occur prior to every op-code.       /WP   Input   Write Protect: This active low pin prevents write operations to               the memory array or the status register.       /HOLD   Input   Hold: The /HOLD pin is used when the host CPU must               interrupt a memory operation for another task. When /HOLD               is low, the current operation is suspended. The device               ignores any transition on SCK or /CS. All transitions on               /HOLD must occur while SCK is low.       SCK   Input   Serial Clock: All I/O activity is synchronized to the serial clock.               Inputs are latched on the rising edge and outputs occur on the               falling edge. Since the device is static, the clock frequency               may be any value between 0 and 20 MHz and may be               interrupted at any time.       SI   Input   Serial Data Input: All data is input to the device on this pin.               The pin is sampled on the rising edge of SCK and is ignored               at other times. It should always be driven to a valid logic               level to meet IDD specifications.               *SI may be connected to SO for a single pin data interface.       SO   Output   Serial Data Output: This is the data output pin. It is driven               during a read and remains tri-stated at all other times               including when /HOLD is low. Data transitions are driven on the falling               edge of the serial clock.               *SO may be connected to SI for a single pin data interface.       VDD   Supply   Supply Voltage (2.7 V to 3.65 V)       VSS   Supply   Ground                  
 
         [0020]     Unlike a serial EEPROM, a FRAM performs write operations at bus speed. No write delays are incurred. The next bus cycle may commence immediately without the need for data polling. It offers virtually unlimited write endurance, and exhibits much lower power consumption than an EEPROM. These capabilities allow a FRAM to be used in applications requiring frequent or rapid writes or low power operation.  
         [0021]     Turning now to the manner of operation of the timepiece  100 , the location data, say 12:00:01, of the analog display is placed on the non-volatile memory  110 . The MCU  102  then reads this data from the non-volatile memory  110 , and transfers such data to the volatile memory  106  for processing.  
         [0022]     The MCU  102  sends a pulse signal to one of the poles  118   a ,  118   b  of the stepping motor  116 . The motor  116  has two poles,  118   a ,  118   b , which must be driven by the MCU  102 , thus receive the pulses from the MCU  102 , alternately. If, say, a pulse signal is sent to the pole  118   a , the next pulse signal has to be sent to the pole  118   b , and the next one has to be sent to the pole  118   a , and so on. When the MCU  102  sends a pulse signal to a pole, e.g. the pole  118   a , it will also measure its “width” by a respective I/O port, e.g. the port  120   a . This measurement is taken at the pole of the step motor  116 .  
         [0023]     The “width” of a pulse signal/supply voltage is the time duration for which the voltage of the pulse signal is at or above a predetermined level. The measurement of the “width” of the supply voltage is “True” when the voltage of the pulse signal is at or above the predetermined level for at least the predetermined period of time; if not, the measurement will be “False”. The latter situation may arise when the supply voltage is low, or when any interruption occurs, e.g. when a battery is suddenly removed from the timepiece  100 .  
         [0024]     If the width measurement is “True”, the step motor  116  will advance to move the analog display. For example, the seconds hand will proceed by one step. The MCU  102  will immediately increase the data in the volatile memory  106  by 1, and so the data in the volatile memory  106  will be 12:00:02. The MCU  102  will also simultaneously update the data of the non-volatile memory  110  to 12:00:02 at bus speed. This means that the volatile memory  106 , the non-volatile memory  110  and the analog display, which is driven by the stepping motor  116 , are synchronized and updated at the same time, together with information of the polarity. The time-related data in the non-volatile memory  110  is thus now 12:00:02. The non-volatile memory  110  thus records the real time displayed by the analog display and reflects the true position of the analog display.  
         [0025]     The MCU  102  then reads from the non-volatile memory  110  and sends the time-related data (which is now 12:00:02) to the volatile memory  106  for processing. The MCU  102  then sends a pulse signal to the pole  118   b , and the width of the pulse signal is measured by the I/O port  120   b . If the width measurement is “True”, the volatile memory  106  and the non-volatile memory  110  will be updated and synchronized at the same time, and the time-related data will then be 12:00:03. The pulse signal sent to the pole  118   b  will also drive the stepping motor  116  to move the analog display to show 12:00:03 accordingly. It can be seen that such an arrangement prevents uncertain polarity from happening after re-connection if there has been a power failure, or the battery is for any reason removed.  
         [0026]     In case the width measurement is “False”, which is considered to be a negative result, the MCU  102  will not increase the data of the volatile memory  106  or that in the non-volatile memory  110 . A “False” pulse width measurement may be caused by unexpected interruption or low power supply voltage. A pulse signal whose width measurement result is “False” can neither drive the stepping motor  116  to advance. Thus, even if a pulse signal is sent to the stepping motor  116 , as its width measurement is “False”, the stepping motor  116  will not advance. By way of such an arrangement, if a pulse signal whose width measurement is “False” is sent, the MCU  102  will stop, leaving the data of the volatile memory  106  and the non-volatile memory  110  and the analog display synchronized but frozen as that right before the sending of the “False” pulse signal. If the power supply is disconnected, the data in the volatile memory  106  will vanish, but that in the non-volatile memory  110  will be intact. This is the case even if a good battery is for any reason removed from the timepiece  100 .  
         [0027]     Once power supply resumes, the MCU  102  will obtain time-related data from the non-volatile memory  110  and activate the radio signal receiver  108  to obtain time signal from the radio source, e.g. a satellite. Time signals may also be inputted into the timepiece  100  by a user operating the switches  112 . The received time is then compared with the position data stored in the non-volatile memory  110 . The MCU  102  will then rapidly output pulse signals to the stepping motor  116  to move the analog display to the position to display the correct current time.  
         [0028]     It can be seen that in the arrangement according to the present invention, as the data in the volatile memory  106  and in particular in the non-volatile memory  110  are updated every second with the confirmation of the advance of the stepping motor  116 , and a “port to pole” polarity assignment, the accuracy of the timepiece  100  is exact and such a timepiece can be used as a radio-controlled grade product.  
         [0029]     A block diagram of an electronic timepiece according to a second embodiment of the present invention is shown in  FIG. 2 , and generally designated as  200 . The operation of the timepiece  200  is also controlled by a micro-controller (MCU)  202  with a processor  204  and a volatile memory  206 , e.g. volatile RAM. The MCU  202  is connected with a radio signal receiver  208 , which receives external time-related radio signal giving the accurate current time. Both the processor  204  and the volatile RAM  206  of the MCU  202  are connected with an internal non-volatile memory  210 , e.g. an EEPROM or a ferroelectric random access memory (FRAM).  
         [0030]     The MCU  202  is connected with two switches  212  operable to input time-related instructions into the timepiece  200  in place of signals received from an outside source by the signal receiver  208 . The MCU  202  sends pulses, through motor drive I/O ports  214   a ,  214   b , to poles  218   a ,  218   b  of a stepping motor  216  to drive a mechanical time display for displaying the time in an analog manner. The MCU  202  also includes two pulse width measurement I/O ports  220   a ,  220   b  for measuring the “width” of the pulses sent via the motor drive I/O ports  214   a ,  214   b  to the poles  218   a ,  218   b  of the stepping motor  216 . In this arrangement, the pulse width measurement I/O ports  220   a ,  220   b  are connected with the respective motor drive I/O ports  214   a ,  214   b  internal of the MCU  202 .  
         [0031]     It should be understood that the above only illustrates examples whereby the present invention may be carried out, and that various modifications and/or alterations may be made thereto without departing from the spirit of the invention. For example, instead of measuring the “width” of the pulse signal, the micro-controller  102 ,  202  may monitor the supply voltage level of the battery, and arrange for the MCU  102 ,  202  to stop sending pulse signals to the motor  116 ,  216  if the voltage level drops below a predetermined level. The same synchronization result can thus also be achieved.  
         [0032]     Alternatively, if the minimum operating voltage of the MCU  102 ,  202  is much higher than the motor driving voltage, then it is also not necessary to check the pulse width of the motor poles nor the supply voltage level. For instance, if the minimum operating voltage of the MCU  102 ,  202  is 2.4V, and the operation voltage of the stepping motor  116 ,  216  is 1.35V, when the supply voltage drops to 2.3V, the MCU  102 ,  202  will stop functioning before it can send out a pulse signal of a voltage lower than 1.35V to the stepping motor  116 ,  216 . The same synchronization among the volatile memory  106 ,  206 , the non-volatile memory  110 ,  210  and the analog display will be maintained.  
         [0033]     As a further alternative, an external voltage regulator may be used for supplying power to the MCU  102 ,  202 . The voltage applied to the MCU  102 ,  202  via the voltage regulator is adjusted to be just above the operating voltage of the MCU  102 ,  202 . When the supply voltage from the voltage regulator drops to the minimum operating voltage of the MCU  102 ,  202 , it will turn off the MCU  102 ,  202 . Thus, instead of the MCU  102 ,  202  detecting and monitoring the supply voltage, it is the voltage regulator which acts as an external controller to control the voltage supply to the MCU  102 ,  202 .  
         [0034]     It should also be understood that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any appropriate sub-combinations.