Abstract:
A digital timepiece is provided with a quartz oscillator, frequency divider and counting circuits, a decoder and a digital electrooptical display device. The timepiece is suitable to operate as a standard digital wristwatch to display the present, i.e., elapsed, time or in the alternative to indicate the remaining time of minutes in the hour or remaining seconds of the minute, i.e., the complement of the elapsed time. A data converter circuit responsive to a manually actuatable switch device is provided for performing the data complement conversion function.

Description:
FIELD OF THE INVENTION 
     This invention relates to a digital wristwatch for displaying elapsed and remaining time information within a predetermined time period. 
     BACKGROUND OF THE INVENTION 
     While digital wristwatches having timekeeping displays have taken on various forms, such wristwatches have been found to have various defects during normal operation. Particularly, digital wristwatches display present or elapsed time, for example 2:23, i.e. twenty three minutes after two o&#39;clock, but they do not present the time remaining within the hour, i.e. 37 minutes. 
     Prior art patents of interest include U.S. Pat. Nos. 3,950,935 issued Apr. 20, 1976 to Okito Naito; 3,822,547 issued July 9, 1974 to Kinji Fujita; 3,950,936 issued Apr. 20, 1976 to Henri J. Oguey et al; and 3,971,205 issued July 27, 1976 to Yasushi Nomura et al. 
     OBJECTS OF THE INVENTION 
     An object of the invention is to provide a digital wristwatch which obviates the above mentioned disadvantages of the prior art timepieces to display the remaining time within a predetermined period. 
     Another object of the invention is to provide a digital display wristwatch which displays the time in hours and minutes and selectively can display the minutes remaining in the hour. 
     A further object of the invention is to provide a digital wristwatch which can display the operating condition of the minutes or seconds time counter and selectively can display the data complement of the operating condition of the minutes or seconds time counter. 
     Still a further object of the invention is to provide an all electronic timepiece which can present time information in digital format such as 2:23, i.e. twenty three minutes after two o&#39;clock, and on demand of the operator can present the minutes, e.g. 37, remaining until the next hour such as 3:00. 
     These and other objectives and features of the present invention will be apparent from the description of a preferred embodiment of the invention, taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of an electronic timepiece according to the invention; 
     FIG. 2 is a logic circuit diagram of the Data Converter in accordance with the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a block diagram of a digital watch with an electrooptical display 10. The watch comprises a time base 1 of a known type, for example, a quartz crystal-controlled oscillator as shown in U.S. Pat. No. 4,117,421 issued Sept. 26, 1978 to Leo Wiesner. The time base 1 is connected to a divider 2, of known type including a certain number of binary stages in cascade, so as to provide an output signal f 1 , of 1HZ for example. 
     The output signal f 1  of divider 2 is supplied to a seconds counter 3, also of a known type, which provides several outputs 4 indicative of the count of seconds and a sixty seconds or one minute count f 2 . The one minute count f 2  is supplied to a minutes counter 5 of known type. 
     The minutes counter 5 provides several outputs 6 indicative of the count of minute pulses f 2  and a count of sixty minutes or one hour pulse f 3 . The one hour pulse f 3  is supplied to an hours counter 7 of known type. 
     The hours counter 7 provides several outputs 8 indicative of the count of hours to a select seconds/minutes-hours circuit 10 of known type. 
     The seconds and minutes output counts 4, 6 of the seconds counter 3 and minutes counter 5, respectively, are supplied to the select seconds/minutes-hours circuit 10. 
     Briefly, the select seconds/minutes-hours circuit 10 is a signal selection means which typically functions to selectively supply, responsive to switch 11, either the seconds output counter signals 4 or the minutes and hours output counter signals 6, 8 to the decoder-driver circuit 9. The elapsed time count comprising either the seconds count signal 4 or the minutes count signal 6, depending upon position of selector switch 11, is supplied as binary coded decimal (BCD) output data signals B-H to the data complement converter 14 which, in turn, supplies decoder-driver circuit 9. Outputs B, C and D give the &#34;units&#34; count and outputs E, F, G, H give the &#34;tens&#34; count. The hours count signal 8 is supplied directly to the decoder-driver as output signal 13 without passing through converter 14. Switch 11 typically is controlled by manual actuation of a push-button actuator (not shown). 
     In the normally open position of switch 11, the minutes and hours count signals 6,8 are supplied, via outputs B&#39;-H&#39; and 13 respectively, to the decoder-driver circuit 9 and the time in hours and elapsed minutes in the hour are shown on display 12. Depression of the push-button and, thereby closure of switch 11 causes the hours and minutes to be extinguished and the seconds to be displayed on display 12. 
     In accordance with the invention, several outputs B through H of the select seconds/minutes-hours circuit 10 representing seconds count or minutes count (elapsed timed count) are supplied to a data complement converter 14. The details of the circuitry of the data complement converter 14 are shown in FIG. 2. Briefly, the data complement converter 14 functions to selectively supply, responsive to switch S, either the data on outputs B through H supplied by the select seconds/minutes-hours circuit 10 or the complement thereof. In other words, the data complement converter 14 functions such that if switch S is open, i.e., not actuated, the binary coded decimal (BCD) information supplied via outputs B through H, e.g. representing either the output count of the seconds or minutes counters 3,5 dependent on the position of switch 11, is coupled via outputs B&#39; through H&#39; to the decoder-driver 9 whereby the elapsed (or present) time is shown on the display 12. With switch S closed, the complement of the binary coded decimal information being supplied via outputs B through H is provided an outputs B&#39; through H&#39;. Thus, with switches 11 and S open (not actuated), the time in hours and elapsed minutes in the hour, for example 2:23, displayed. With switch 11 open and switch S closed (actuated), the time in hours and remaining minutes in the hour, for example 2:37, or alternatively only the remaining minutes, i.e., 0:37 (typically referred to as thirty seven minutes to three o&#39;clock) is displayed. With switch 11 closed and switch S open, the elapsed seconds in the minute, for example 45, are displayed. With switches 11 and S closed, the remaining seconds in the minute, for example 15, are displayed. In this manner, the operator of the watch is given the option to perceive time in the present (elapsed) format and/or in the future or remaining format. 
     FIG. 2 shows a detailed circuit drawing of the data complement converter 14. The following Boolean Algebraic expressions in Table 1 describe the normal/complementary selection and complementary conversion functions performed by the data complement converter 14. 
     
                       TABLE 1______________________________________Units: Minutes or Seconds               Tens: Minutes or Seconds______________________________________E&#39; = -S E + S[E-F(G-H + -GH)]               A&#39; = 0F&#39; = -S F + S[F(-G + -H) + -E-FGH]               B&#39; = -S B + S -B -CG&#39; = -S G + S[GH + E-G + F-G-H]               C&#39; = CH&#39; = H              D&#39; =-S D + S-D______________________________________ 
    
     Table 2 shows the truth table for the logic circuit illustrated in FIG. 2 
     
                       TABLE 2______________________________________UNITS:           COMPLEMENT UNITS:MINUTES/SECONDS  MINUTES/SECONDSDIGIT E&#39;     F&#39;     G&#39;   H&#39;  DIGIT E&#39;   F&#39;   G&#39;   H&#39;______________________________________0     0      0      0    0   0     0    0    0    01     0      0      0    1   9     1    0    0    12     0      0      1    0   8     1    0    0    03     0      0      1    1   7     0    1    1    14     0      1      0    0   6     0    1    1    05     0      1      0    1   5     0    1    0    16     0      1      1    0   4     0    1    0    07     0      1      1    1   3     0    0    1    18     1      0      0    0   2     0    0    1    09     1      0      0    1   1     0    0    0    1______________________________________TENS:            COMPLEMENT TENS:MINUTES/SECONDS  MINUTES/SECONDSDIGIT B&#39;     C&#39;     D&#39;       DIGIT B&#39;   C&#39;   D&#39;______________________________________0     0      0      0        5     1    0    11     0      0      1        4     1    0    02     0      1      0        3     0    1    13     0      1      1        2     0    1    04     1      0      0        1     0    0    15     1      0      1        0     0    0    0______________________________________