Integrated Circuit Solid State Watch

Abstract

Disclosed is a solid state electronic wristwatch with no moving parts. A crystal oscillator supplies a timing signal through a binary divider and display actuator to an electro-optical display in the form of a digital array of light-emitting diodes. The same display is used for both minutes and seconds and all displays are driven from the same decoder. The vast majority of the electrical components of the watch are incorporated in one or more large-scale integrated circuits.

Parent Case Text

This application is a continuation-in-part of copending application Ser. No. 138,547, filed Apr. 29, 1971, in the name of Bruno M. Dargent entitled "Solid State Watch Incorporating Large-Scale Integrated Circuits", now U.S. Pat. No. 3,714,867.

Description

This invention relates to a solid state timepiece and more particularly to an electronic watch which employs no moving parts. In the present invention, a frequency standard in the form of a crystal oscillator acts through solid state electronic circuit dividers and drivers to power in timed sequence the light-emitting diodes of an electrooptic display. Low power consumption and small size and weight are achieved through the use of complementary MOS circuits to produce what is in essence a miniaturized fixed program computer. In particular, the present invention is directed to a wristwatch in which substantially all of the electrical circuitry may be constructed using large-scale integrated circuit techniques.

Battery-powered wristwatches and other small portable timekeeping devices of various types are well known and are commercially available. The first commercially successful battery-powered wristwatch was of the type shown and described in assignee's United States Reissue Patent No. RE 26,187, reissued Apr. 4, 1967, to John A. Van Horn et al for "Electric Watch." Electric watches of this type employ a balance wheel and a hairspring driven by the interaction of a current-carrying coil and a magnetic field produced by small permanent magnets.

In recent years, considerable effort has been directed toward the development of a wristwatch which does not employ an electromechanical oscillator as the master time reference. In many instances, these constructions have utilized a crystal controlled high frequency oscillator as a frequency standard in conjunction with frequency conversion circuitry to produce a drive signal at a suitable timekeeping rate. However, difficulties have been encountered in arriving at an oscillator frequency converter combination having not only the required frequency stability but also sufficiently low power dissipation and small size to be practical for use in a battery-powered wristwatch.

In order to overcome these and other problems there is disclosed in assignee's U.S. Pat. No. 3,560,998, issued Feb. 2, 1971, a high frequency oscillator type watch constructed using low power complementary MOS circuits. The oscillator/frequency converter combination of that patent is described as suitable for driving conventional watch hands over a watch dial or, alternatively, for selectively actuating the display elements of an optical display in response to the drive signal output of the converter. In assignee's U.S. Pat No. 3,576,099, issued Apr. 27, 1971, there is disclosed an improved watch construction in which the optical display is described as a plurality of light-emitting diodes which are intermittently energized to assure a minimum power consumption and an increasingly long life for the watch battery.

An improve watch construction of this general type incorporating solid state circuits and integrated circuit techniques is disclosed in assignee's copending U.S. Pat. application Ser. No. 35,196, filed May 6, 1970 U.S. Pat. No. 3,672,155. The present invention is directed to an improved watch construction of the same general type as disclosed in the above-mentioned application and patents and one which utilizes no moving parts to perform the timekeeping function. In particular, the present invention is directed to an electronic wristwatch construction in which substantially all of the electrical components are formed as large-scale integrated circuits so as to reduce both the cost and size of the watch components. Through the use of large-scale integrated circuits, it is possible to utilize standardized, mass production fabrication of the electrical components which not only substantially reduces the cost of the watch, but, because of the reduction in size, makes more space available in a conventional wristwatch case for the watch battery and other wristwatch components.

In the present invention, the wristwatch comprises a frequency standard, preferably operating at a frequency of 32,768 Hz and formed as a crystal controlled complementary MOS inverter used as an oscillator. Output signals from the frequency standard pass through a frequency converter, preferably in the form of a multi-stage binary frequency divider constructed of complementary MOS transistors. The signal is divided down in the frequency converter to produce an output of 1 Hz. The display actuator is formed by a plurality of registers, gates and a decoder which drives an electro-optical display, preferably in the form of a bar segment arrangement of light-emitting diodes. Additional functions performed by the large-scale integrated circuit involve time setting, resetting, switching, and display intensity control.

Through the use of NOR and NAND logic circuits and complementary MOS transistors, it is possible through the present invention to construct a solid state watch in which all but a very few of the electrical components may be formed using large-scale integration, commonly referred to as LSI.

The watch display preferably comprises a red colored filter which passes cold red light from a plurality of gallium arsenide phosphide light-emitting diodes which are preferably arranged in a seven bar segment array. The light-emitting diodes are energized in appropriate time relationship with an effective brightness determined by an intensity control circuit utilizing a photosensitive detector. Situated on the front of the watch adjacent the display is a pushbutton demand switch which, when depressed, instantly activates the appropriate visual display stations. Minutes and hours are programmed to display for one and one-quarter seconds with just a touch of the demand switch. Continued depression of this switch causes the minute and hour data to fade and the seconds to immediately appear. The seconds continue to count as long as the wearer depresses the demand button. Computation of the precise time is continuous and completely independent of whether or not time is displayed.

Setting is accomplished by actuating either an hour-set switch or a minute-set switch. The hour-set switch rapidly advances the hours without disturbing the time-keeping of the minutes and seconds. Actuation of the minute-set switch automatically zeros the seconds while advancing the minutes to the desired setting.

The watch of the present invention is virtually shockproof and waterproof regardless of the environment in which it is placed. The electrical components and the display may be encapsulated with a clear potting compound so that no mechanical forces or corrosive elements can attack the electronics. Since there is no conventional stem for winding or setting, the small shaft sealing problem is eliminated. No maintenance or repair is normally necessary since the components are sealed and inaccessible to influences from the outside world. All solid state electrical components, including the light-emitting diode displays, have a virtually unlimited life.

Important features of the present invention include the use of an integrated circuit with a single decoder for decoding the time information to be displayed. In addition to time, the display can be used with the decoder to show day and month, as well as a.m. and p.m. of time. The display digits are individually strobed and special connections are provided to turn on the display at all times for use as a clock, for use as an alarm clock, to enter special information such as the date, month, a.m. and p.m. times. In addition, a connection is provided as a carryout from the hours register for use with a calendar circuit so that the watch circuit may be used in conjunction with other circuitry to have and show on the same display days and months.

It is therefore one object of the present invention to provide an improved electronic wristwatch.

Another object of the present invention is to provide a wristwatch which utilizes no moving parts for performing the timekeeping function.

Another object of the present invention is to provide a completely solid state electronic wristwatch in which the display is in the form of a plurality of light-emitting diodes.

Another object of the present invention is to provide an electronic watch including an illuminated display in which the light level is automatically compensated to the viewing conditions for increased eye comfort and reduced power drain.

Another object of the present invention is to provide an improved timepiece having reduced size and cost for incorporation in a conventional man's wristwatch case.

Another object of the present invention is to provide an improved solid state timepiece in which substantially all of the electrical components are formed from large-scale integrated circuits.

Another object of the present invention is to provide a simplified wristwatch construction and yet one which has increased versatility of operation so that other information can be displayed and so that the watch can be used with other external circuits.

These and further objects and advantages of the invention will be more apparent upon reference to the following specification, claims, and appended drawings, wherein:

FIG. 1 is a perspective view of a conventional sized man's wristwatch constructed in accordance with the present invention;

FIG. 2 is a simplified block diagram showing the principal components of the wristwatch of FIG. 1;

FIG. 3 shows a seven bar segment light-emitting diode array forming a part of the display of the wristwatch of FIGS. 1 and 2;

FIG. 4 is a diagram of an oscillator forming the time base or frequency standard of FIG. 3;

FIG. 5 is a more detailed circuit diagram of the wristwatch of the present invention showing in block form the large-scale integrated circuit;

FIGS. 6a, 6b, and 6c, taken together show a detailed block diagram of the large-scale integrated circuit of FIG. 5; and

FIG. 7 shows the arrangement of the light-emitting diode bar segments in the watch of the present invention.

Referring to the drawings, the novel watch of the present invention is generally indicated at 10 in FIG. 1. The watch is constructed to fit into a watch case 12 of approximately the size of a conventional man's wristwatch. The case 12 is shown connected to a wristwatch bracelet 14 and includes a display window 16 through which time is displayed in digital form as indicated at 20. The window may desirably be closed off by a red light filter to enhance the display. Mounted on the case 12 is a pushbutton demand switch 18 by means of which the display 20 may be actuated when the wearer of the wristwatch 10 desires to ascertain the time.

In normal operation, time is continuously being kept but is not displayed through the window 16. That is, no time indication is visible through the window and this is the normal condition which prevails in order to conserve battery energy in the watch. However, even though the time is not displayed through the window 16, it is understood that the watch 10 continuously keeps accurate time and is capable of accurately displaying this time at any instant. When the wearer desires to ascertain the correct time, he depresses the pushbutton 18 with his finger and the correct time immediately is displayed at 20 through the window 16, which shows a light-emitting diode display giving the correct time reading of 10:10, namely, ten minutes after ten o'clock. The hours and minutes, i.e., 10:10, are displayed through the window 16 for a predetermined length of time, preferably one and one-quarter seconds, irrespective of whether or not the pushbutton 18 remains depressed. The exact time of the display is chosen to give the wearer adequate time to consult the display to determine the hour and minute of time. Should the minutes (or hours) change during the time of display, this change is immediately indicated by advancement of the minute (or hour) reading to the next number, i.e., 11, as the watch is being read. If the pushbutton 18 remains depressed, at the end of one and one-quarter seconds the hours and minutes of the display are extinguished, i.e., they disappear, and simultaneously the seconds reading is displayed through the window 16. The advancing seconds cycling from 0 to 59 continue to be displayed through window 16 until the pushbutton switch 18 is released.

FIG. 2 is a simplified block diagram of the principal components of the watch 10 of FIG. 1. The watch comprises a time base or frequency standard 26, preferably chosen to produce an electrical output signal on lead 28 at a frequency of 32,768 Hz. This relatively high frequency is supplied to a frequency converter 30 in the form of a divider which divides down the frequency from the standard 26 so that the output from the converter 30 appearing on lead 32 is at a frequency of 1 Hz. This signal is applied to the display actuator 34 which in turn drives the display 20 of the watch by way of electrical lead 36. While only an hours and minutes display is shown, it is understood, as previously described, that the hours and minutes are first displayed for a predetermined time and if the pushbutton remains depressed, the hours and minutes are extinguished and the seconds become visible. The same display diodes are used for both minutes and seconds since these are not displayed simultaneously, thus minimizing the power drain from the watch battery. For a more detailed description of the physical construction and mode of operation of the watch of the present invention, reference may be had to assignee's copending United States patent application Ser. No. 35,196, filed May 6, 1970 now U.S. Pat. No. 3,672,155, the disclosure of which is incorporated herein by reference. ,

In the preferred embodiment, the display takes the form of a seven bar segment array of light-emitting diodes, preferably formed of gallium arsenide phosphide which emit light when energized in the visible red region of the spectrum. FIG. 3 shows a single display station or numeral 38 consisting of seven light-emitting diodes 40, 42, 44, 46, 48, 50, and 52 of elongated shape and arranged so that by lighting an appropriate combination of the bars or segments any one of the numbers 0 through 9 may be displayed. While a seven bar segment display is preferred, it is apparent that other type displays, such as a 27 dot matrix display, may be used.

FIG. 4 is a circuit diagram of the frequency standard 26 of FIG. 2. The frequency standard is a crystal controlled oscillator comprising a complementary pair of integrated circuit enhancement transistors including a P-channel transistor 53 and an N-channel transistor 54 connected between the positive supply terminal 56 and the other or grounded side of the power supply, as indicated at 59, to form a complementary MOS inverter. The F and F outputs for the divider 30 of FIG. 2 are developed on output leads 58 and 60 in FIG. 4. The divider is preferably of the type shown and described in assignee's U.S. Pat. No. 3,560,998, the disclosure of which is incorporated herein by reference. Transistors 53 and 54 in FIG. 4 form an MOS integrated circuit inverter and have connected across them a bias resistor 62, a quartz crystal 64, and a variable tuning capacitor 66 in series with the crystal. Connected between the positive power supply terminal 56 and the transistor gate is a protective diode 68. A .pi. network configuration made with two capacitors from input and output of the oscillator to ground improves stability and makes the oscillator very little circuit (CMOS) dependent.

The active element of the oscillator 26 of FIG. 4 is the complementary MOS inverter with the protective diodes 68 and 69 between the gate and source of each of the transistors 53 and 54. This inverter can be a separate device but is preferably a part of the integrated circuit divider chain as more fully described below. The bias resistor 62 is used to bias the inverter into the linear region by making the input voltage equal to the output voltage under static conditions. Once the oscillator is under the control of the crystal, the bias resistor 62 is no longer a significant part of the circuit. A typical value for the bias resistor is about 22 megaohms. Quartz crystal 64 is of the type normally used in oscillators where the Q is high and the series resistance is low. The shunt capacitance of the crystal should be less than 10 picofarads. Tuning capacitor 66 is used to adjust the oscillator over a narrow range of frequencies. The value of this capacitor is normally between 0.5 and 5.0 picofarads. Oscillator 26 provides the two-phase output required by the first stage of the divider chain. The oscillator has two resistors R.sub.1 and R.sub.2 to control the current in the oscillator and make the circuit device independent. An inverter is used on the output of the oscillator as a shaping circuit in order to enter a square wave signal into the divider.

The gate protective diodes 68 and 69 are desirable because in MOS transistors it is easy to permanently damage the transistor by applying a voltage to the gate which is higher than the source or substrate voltage. A high positive or negative potential on the gate will cause arcing across the gate dielectric which will create pinholes in the dielectric and alter the transistor characteristics. By adding the diodes 68 and 69 between the gate and source of the transistors, a current path is provided when the gate voltage is higher than the source potential.

FIG. 5 is a circuit diagram of the watch 10 of the present invention with like parts bearing like reference numerals. Integrated circuit portions of the watch are illustrated by the large block 70. This block may be formed of one or several integrated circuit chips but it is understood that all the components within block 70 (which components are illustrated in FIGS. 6a, 6b, and 6c) are formed by large-scale integrated circuit techniques. In addition to the integrated circuit 70 in FIG. 5, the watch comprises a battery 72 which, by way of example only, may comprise a conventional 3 volt wristwatch battery. Connected to the positive side of the battery is a resistor 73 for a purpose more fully described below and the battery energizes the display 38 which is shown in FIG. 5 as consisting of a pair of hours stations comprising the digit station 74 and tens station 76 and a pair of combination minutes and seconds stations comprising digits station 78 and tens station 80. In addition, the display 38 includes a pair of colon dots 81, each formed by a single light-emitting diode. The display stations are energized from integrated circuit 70 connected to battery 72 by way of a plurality of leads 79. The circuit is completed from the leads 79 to the anodes of the light-emitting diodes and the cathodes of the light-emitting diodes are individually connected to the other side of the power supply through strobing or switching N-P-N junction transistors 82, 84, 86, 88, 90, and 92. There is a separate lead 79 for the total number of bar segments in a display station. That is, with a seven bar segment display, there are seven leads 79, each one connected to a separate bar segment of each station as more fully described below. However, all of the cathodes of each station are connected in common through the N-P-N junction transistor for that display. The two bar segments 94 and 96 for the hours tens display have their cathodes connected to transistor 82 as do the colon dots 81. All cathodes of the hours units station 74 are connected to transistor 84. Display stations 78 and 80 are used to display both minutes and seconds so that station 80 has the cathodes of all diodes connected to transistor 86, referred to as the minutes transistor, and to transistor 90, which acts as the seconds transistor. Similarly, all the diode cathodes of display station 78 are connected to a minutes transistor 88 and a seconds transistor 92. These transistors have their bases returned to the integrated circuit 70 through current limiting resistors 98, 100, 102, 104, 106, and 108, the emitters of the transistors being connected in common to ground, i.e., the negative side of the power supply battery 72 as indicated at 110.

The anodes of the bar segment diodes are energized from bipolar driver transistors illustrated in FIG. 5 as the P-N-P junction transistors 112, 114, 116, 118, 120, 122, and 124. Since the greatest number of bar segments at any display station is seven, there are seven driver transistors and seven leads 79. The transistor collectors are connected to the display diodes through individual ones of current limiting resistors 126 and the driver transistor bases are connected to the integrated circuit 70 through protective resistors 128. The emitters of the driver transistors are connected in common as at 130 to the positive side of power supply battery 72.

The external components of the oscillator 26 in FIG. 5 are the crystal 64, the variable capacitor 66, and the bias resistor 62 and .pi. netowrk capacitor. The of the oscillator shown in FIG. 4 are incorporated in the integrated circuit 70 of FIG. 5. Also external to the integrated circuit is a demand or read switch 132 which is closed when the button 18 of FIG. 1 is depressed. Further manually operated switches external to the integrated circuit 70 are minute-set switch 134 and hour-set switch 136. These switches are connected across battery 72 from the positive side of the battery to ground through respective series resistors 138, 140, and 142. The resistors associated with the switches are used in order to ground the corresponding inputs, otherwise the corresponding inputs would be floating and could be anything. When closed, the switches are used to switch the input voltages from ground to plus.

A feature of the watch of the present invention is that the intensity of the light emitted from the display diodes is varied in accordance with ambient light. That is, the diode light intensity is increased for greater contrast when the ambient light is bright, such as during daytime display, whereas the intensity of the light from the diodes is decreased when ambient light decreases. The automatic display intensity control circuitry is generally indicated at 144 in FIG. 5 and comprises a photosensitive resistor 146 suitably mounted on the face of the watch connected to the positive side of battery 72 and to a resistor 148 and capacitor 150. These components are connected to the positive side of the power supply through series resistor 152. Other external components connected to integrated circuit 70 include an internal information lockout lead 154, a transmission gate control lead 156, and an optional input or continuous display lead 158, all normally grounded. A further connection to ground is through resistor 157 and the integrated circuit 70 is also provided with a carry out lead and terminal 159.

FIGS. 6a, 6b, and 6c taken together show is a detailed block diagram of the integrated circuit 70 of FIG. 5. In FIGS. 6a, 6b and 6c, like parts bear like reference numerals. FIG. 7 illustrates the arrangement of the light-emitting diode segments of the display.

Referring to FIGS. 6a, 6b, 6c and 7, a signal having a frequency of 32,768 Hz is supplied from oscillator 26 over lead 28 to the divider input terminal 160. The divider 30 is a 14 stage non-resettable counter forming the frequency converter 30 of FIG. 2. The counter is formed from 14 stages of binary flip-flops in a counting chain and each stage is comprised of complementary MOS transistors as previously described. The output of the 12th stage of the divider, having a frequency of 8 Hz, is applied by way of a lead 162 to the input of a three-stage resettable counter 164 comprising three stages of MOS complementary symmetry transistor flip-flops which produce an output on lead 166 having a frequency of 1 Hz. The 8 Hz signal from the divider is also applied by way of a lead 168 to a four-stage flip-flop decade counter 170, the output of which counter or control timer 170 controls a one and one-quarter second timing flip-flop 172.

The 1 Hz signal on lead 166 is applied to a seconds units storing register 172 which divides by ten and whose output is in turn connected to a seconds tens register 174 which divides by six. The seconds tens register in turn has its output connected to a minutes units register 176 which again divides by ten and the output of this register is connected to a minutes tens register 178 which divides by six. The output of register 178 is in turn connected to a divide by 12 hours register, generally indicated at 180. These registers are all comprised of binary chains of complementary MOS transistor pairs and the individual stages, except for the control terminals, are in all respects similar to the individual stages of the binary dividers 30 and 164. For a detailed discussion of an individual stage forming a stage of either the divider 30, divider 164, or one of the registers 172, 174, 176, 178, and 180, reference may be had to assignee's U.S. Pat. No. 3,560,998.

Output signals indicative of seconds units of time are developed in register 172 and these are applied through four selection gates 182, and through four input gates 184, to a decoder 186. The decoder 186 converts the 8-4-2-1 binary coded decimal signals from the register 172 into suitable drive signals for the displays which are applied to the light-emitting diodes of the display through the buffer amplifiers 188. The individual bar segments are labeled a through g and the relationships of the segments and their interconnections to the outputs of the buffer amplifiers 188 is illustrated in FIG. 7. That FIGURE shows the hours tens station 76 and the hours units station 74, along with the colon dots 81. While only the hours station 74 is illustrated in FIG. 7, it is understood that the outputs of the buffer amplifiers 188 are also connected to the corresponding bar segments of the combination minutes and seconds stations 78 and 80 of FIG. 5, each of these stations being in all respects identical to station 74. That is, output a from buffer amplifier 188 is not only connected to the a bar segment of station 74, but is also connected to the corresponding segment of stations 78 and 80 of FIG. 5. The correspondingly labeled other outputs of buffer amplifiers 188 are connected to the corresponding other bar segments of each of the stations 74, 78, and 80. Outputs b and c are also connected to the anodes of the colon dot diodes and outputs a and d from the buffer amplifiers 188 are connected to the anodes of the two diodes 94 and 96 forming the hours display. These diodes are simultaneously on or off to display a "1" or nothing at all in correspondence with the hours tens digit of time.

Register 174 in FIG. 6b is similarly connected through four selection gates 190 to the input gates 184 and to the decoder 186, the input gates 184 and decoder 186 being common to all the registers. Register 176 is connected to the input gates 184 through selection gate 192 and register 178 is similarly connected to the input gates through selection gates 194. Finally, hours register 180 is connected to the input gates through two sets of selection gates, i.e., first set 196 and second set 200. The integrated circuit 70 of FIG. 6 performs the functions of time base generation, time storage and information decoding, as well as the miscellaneous functions of display timing, automatic intensity control and display selection. The circuit is designed to operate 2.5 to 3.2 volts and to use 1.00 inch light-emitting diode displays. The time base generator portion of the circuit consists of external components (crystal, resistor, and trimming capacitor), an inverter used as an oscillator and a 14-stage non-resettable counter 30, as well as the three-stage resettable counter 164. The 14-stage counter 30 provides the frequencies used throughout the system to perform such functions as timing, setting, resetting, switching, and display intensity control. The three-stage counter 164 is resettable because it acts as a "hold" circuit during minute setting. After the minutes have been set, this counter remains in the reset mode which keeps a signal from passing into the second storage register 172 until the read or demand button 18 of FIG. 1 has been depressed and the read switch 132 of FIG. 5 closed. This counter consists of three stages so that the error upon starting is no greater than one-eighth of a second.

The time storage portion of the circuit consists of three registers, two divide by 60 and another divide by 12. The first divide by 60 register is resettable and is used to accumulate seconds. Both divide by 60 registers are subdivided into divide by ten and divide by six sections such that the first divide by 60 register is formed by the register sections 172 and 174 and the second divide by 60 register is formed by register sections 176 and 178. This division is provided because the time information must be displayed as decimal numbers. The divide by 12 register 180 displays the numbers 1 through 12 and resets to 1. This is accomplished by making the first flip-flop 202 in the divide by 10 section, indicated by the bracket 204, non-resettable. The first four flip-flops enclosed within bracket 204 constitute the divide by 10 section, the next flip-flop 206 controls the tens of hours and the last flip-flop 208 is used to insure positive resetting. At the count of 10, 8 and 2 are detected. This sets the tens of hours flip-flop 206 and triggers the resetting flip-flop 208 which resets stages 2, 4, and 8. Stage 1, i.e., flip-flop 202 is already at "0" so the units hours decodes to zero. However, at 13, an AND gate 210 reads the tens of hours in stages 1 and 2. This toggles the tens of hours flip-flop 206 by way of lead 212 back to zero and resets stages 2, 4, and 8 by way of lead 214. Stage 1, i.e., flip-flop 202, is not reset and therefore the number "1" is decoded. However, this happens so rapidly that the number 13 is never displayed.

It is a feature of this invention that only one decoder 186 is used in conjunction with a strobing circuit, generally indicated at 216, by means of which the digits are individually strobed. The six strobe outputs, labeled A, B, C, D, E, and F, of the strobe circuit 216 are applied to the corresponding and similarly labeled lines 218, 220, 222, 224, 226, and 228 of the selection gates 182, 190, 192, 194 and two sets in group 196, such that these selection gates are enabled in accordance with the strobe outputs. A second set of strobe circuit outputs, labeled S.sub.1, S.sub.2, S.sub.3, S.sub.4, S.sub.5, and S.sub.6, are applied as correspondingly labeled inputs in FIG. 5 to the strobe transistors 82, 84, 86, 88, 90, and 92. The strobing outputs are such that the sequence of the display is as follows: (a) tens of hours and colon, (b) units of hours, (c) tens of minutes, (d) units of minutes, or (a) nothing, (b) nothing, (c) tens of seconds, (d) units of seconds if seconds are displayed, an then the cycle repeats.

It is apparent from FIG. 6 that a common decoder 186 is used for all numerals to be displayed. The high frequency output of oscillator 26 is lowered in frequency by a series of binary divider stages in divider 30. This divider produces several output frequencies including a 8 Hz output which is fed into the register 164 to produce a 1 Hz output on lead 166. The 1 Hz output is fed into the counting registers 172, 174, 176, 178, and 180 where it is further divided by 10, 6, 10, 6, and 12, corresponding to the digits needed to display seconds, minutes and hours. The binary coded decimal outputs of all the dividers in the counting registers are fed into corresponding selection gates 182, 190, 192, 194, and 196. These gates are controlled by the strobe circuit 216 and the number passing through the input gates 184 into the decoder-driver 186 is determined by this strobe circuit.

In the operation of the system, the timer 170 controls the strobing circuit. When the demand switch is depressed, the minutes and hours are displayed for one and one-quarter seconds and if the demand switch remains depressed, the display automatically switches to seconds. Therefore, it is necessary for the strobe circuit to strobe only four numerals at any one time, although it controls all six numerals. After the strobing circuit 216 selects the register to be read, the time stored in that register (in binary coded decimal form) passes through the set of selection gates opened by the strobe circuit and through the input gates 184 which act as an interface to the decoder 186. This decoder changes the B-C-D information into the output necessary to form intelligible numerals. The strobing circuit 216 not only chooses which counting register will be read, but also completes the anode circuit for the corresponding numeral diodes. Therefore, only one numeral can be on at any one time but because the strobing action takes place so rapidly, it appears that as many as four numerals are lighted simultaneously.

Divider 30 produces a 256 Hz output (.phi.7) and a 128 Hz output (.phi.8) which are applied to selected ones of four NAND gates 215 in strobe circuit 216. These signals are in turn passed through four NOR gates 217 which also receive a signal by way of lead 250 from the timer control flip-flop 248. The outputs A, B, C, D, E, and F from strobe circuit 216 are applied to the corresponding sets of selection gates 182, 190, 192, 194, and 196 to control which numerals are to be displayed as described above. The other strobe outputs S.sub.1, S.sub.2, S.sub.3, S.sub.4, S.sub.5, and S.sub.6 are applied to the bases of transistors 82, 84, 86, 88, 90, and 92 of FIG. 5 to complete the anode-cathode circuits of the display diodes. In this way, it is possible for the strobe circuit to control which information from which register will pass to the decoder 186 and this B-C-D information must pass through the input gates 184 which are provided to prevent interference between the several outputs from the selection gates as they enter the decoder. The output of the decoder-driver 186 provides power by way of driver transistors 112, 114, 116, 118, 120, 122, and 124 in FIG. 5 to those segments or display diodes which are to be activated to display the number corresponding to the B-C-D input number.

Display intensity control is obtained by varying the duty cycle of the strobe drive signal supplied to the strobing circuit 216 by way of a lead 230, this signal also being supplied as an ON-OFF signal by way of lead 232 to the input gates 184. The signal on lead 232 insures that the diodes, even when on, will blink on and off but at a rate such as 64 Hz so as to give the appearance of being continuously energized. The ON-OFF signal on lead 232 and the strobe drive signal 230 is therefore a 64 Hz signal or series of short width pulses having a repetition rate of 64 Hz in which the pulse width may be varied to vary the average duty cycle of the signal. This is accomplished by taking signals from the third, fourth, fifth and sixth stages of divider 30, which signals are identified as .phi.3, .phi.4, .phi.5, and .phi.6, and applying them to the four inputs of a NAND gate 234. The output from this gate on lead 236 is a series of 64 Hz pulses having a very short pulse width. These are applied through a NAND gate 238 by way of terminal 240 (labeled terminal 9) to the display intensity control 144 of FIG. 5. Resistor 152 in series with light sensor 146 gives increased linearity and the circuit in essence acts as a multivibrator which is triggered at a rate of 64 Hz from the divider 30 and NAND gate 234. The length of the output pulse generated by the multivibrator 144 and applied to terminal 242 (labeled terminal 10 in FIG. 6) is determined primarily by the fixed capacitor 150 and the light sensitive resistor 146 in FIG. 5. These 64 Hz pulses, having a variable width and therefore a variable duty cycle in accordance with ambient light intensity, are supplied to the strobe circuit 216 by way of lead 230 and as ON-OFF or blinking signals to the input gates 184 to control the illumination duty cycle of the display diodes. The duty cycle in each digit is a maximum of 25 percent modulated by the light control network 144 to as low as 1.56 percent in the dark (6.25 percent of 25 percent). The strobing signals used for the minutes are also used for the seconds but in the preferred embodiment as illustrated, the minute display is also used for displaying seconds.

The display timer is generally indicated at 170 in FIG. 62. This timer automatically turns off the hours and minutes after one and one-quarter seconds. A momentary depression of the read or demand button 18 produces a corresponding closure of the manual switch 132 in FIG. 5 and this completes a setting circuit, i.e., connects B+ to terminal 244 in FIG. 6, which is connected by way of lead 246 and acts to set a timing flip-flop 248. This flip-flop is reset only after the decade counter 170 has counted ten pulses of an 8 Hz signal applied to it over lead 168. As long as flip-flop 248 is in the set condition, it puts the proper signal on lead 250 so that only the hours and minutes are displayed. If the read or demand button remains depressed after the decade counter 170 had completed a cycle and supplied a reset signal by way of lead 252, the display automatically reverts to a display of seconds.

Divider 30 is a 14-stage binary device and produces a 2 Hz output on lead 254 which is combined with a 4 Hz signal on lead 256 and an 8 Hz signal on lead 258 in NAND gate 260 to produce a 2 Hz setting signal on lead 262 which has a very short pulse width. This signal is applied through NAND gate 264 to the input of minutes register 176 and through NAND gate 266 to the input of hours register 180. Closure of the hours-set switch 136 in FIG. 5 applies B+ to terminal 268 and the short pulse width 2 Hz setting signal passes through NAND gate 266 to the hours register setting the hours display at the "fast" rate of two hours per second. Closure of minute-set switch 134 in FIG. 5 applies B+ to minute-set terminal 270 causing the 2 Hz setting signal to pass through gate 264 to the input of minute units register 176. This is a "slow" or fine setting with the minutes advanced at two per second. A display during setting is assured by connecting hours-set terminal 268 and minutes-set terminal 270 through NOR gate 272 to the display intensity control circuit connected to terminals 240 and 242.

Operation of the minute-set switch applies a reset impulse from minute-set terminal 270 through NOR gates 274 to lead 276 which resets counter 164 and the seconds registers 172 and 174 to zero. In this way, the seconds display is automatically zeroed when the minutes are set. Counting is resumed in the seconds registers as soon as the pushbutton 18 is depressed and the read switch 132 closed.

Decoder 186 is used to convert the 8-4-2-1 binary coded decimal codes from the registers into a seven segment display code for the display stations. It is used for the units and tens of seconds, for the units and tens of minutes, and for the units of hours. As previously described, the tens of hours are either on or off to display a "1" or nothing. The tens of hours display is connected to the a and d outputs of the decoder while the colon is connected to the b and c outputs so that a B-C-D "1" turns on the colon only and a B-C-D "0" turns on the colon and the tens of hours. The proper coded information is generated in the large-scale integration circuit 70 itself. A special feature of the decoder is that special information can be fed into it according to the following table:

TABLE

B-C-D input a b c d Display 0 0 0 0 1 : hours 1 0 0 0 : 0 1 0 0 1 : AM 0 1 1 0 1 : PM month 0 1 0 1 : AM 0 1 1 1 : PM

that is, the display can be used with the decoder to show date and month, A.M. and P.M. being shown with one or the other dot of the colon. This special information is introduced through leads 274, 276, 278, and 280, labeled Q.sub.1, Q.sub.2, Q.sub.3, and Q.sub.4, respectively, all under the control of an input terminal 282 which is connected to the transmission gate control lead 156 in FIG. 5 and is normally grounded. Terminal 282 allows or prevents any signal to pass through the corresponding transmission gates, generally indicated at 284. That is, if terminal 282 is grounded, the transmission gate acts as an open circuit. If terminal 282 is connected to B+, the transmission gates 284 are short circuits.

Also provided in the circuit is an optional input terminal 286 connected to the optional input lead 158 in FIG. 5 and normally grounded, as well as an internal information lockout terminal 288 coupled to the strobe circuit 216 and connected to the internal information lockout lead 154 of FIG. 5 and also normally grounded. When optional input terminal 286 is connected to a positive signal, this positive signal is applied to a NAND gate 290 so that decade timer 170 is defeated and the display hours and minutes are on all the time that a positive signal is applied to terminal 286. When internal information lockout terminal 288 is connected to a positive signal, the strobing switch outputs S.sub.1, S.sub.2, S.sub.3, and S.sub.4 are not disturbed but the decoder is no longer able to send the B-C-D information from the registers because the control signal outputs A, B, C, and D from the strobe circuit 216 are stopped. With these circuits connected to the terminals 282, 286, and 288, it is possible by using the proper combinations to (1) turn ON the display all the time for use as a clock, (2) defeat the reading of the internal time and read any information entered at terminals 274, 276, 278, and 280, (3) read on terminals 274, 276, 278, and 280 the time in the watch in B-C-D form (with the exception of the seconds at any time). When the display is ON all the time, it may be used as an alarm clock. It is also possible to (4) use this circuit with another one to have and show on the same display days and months.

Additional features of the circuit 70 include a carryout terminal 292 connected to external terminal and lead 159 in FIG. 5 to provide a carryout of the hours register for use with a calendar circuit. Also, it should be noted that + and - leads of the oscillator 26 are available so that limiting resistors can be introduced, that the output of the oscillator is available for use if desired.

It is apparent from the above that the present invention provides an improved solid state watch construction in which a vast majority, i.e., substantially all, of the electrical components are formed from a large-scale integrated circuit. The circuit is fabricated in its entirety from complementary symmetry MOS transistor and only the buffers in the circuit carry high currents so that small transistors can be used throughout substantially the entire circuit.

Important features of the invention include an electronically regulated timekeeping device characterized by sufficiently small size and low power dissipation to be practical for use in a device of wristwatch size. Through the use of large-scale integration, the circuit may be more economically manufactured and permits more space in a conventional wristwatch case for a battery, crystal and other components. While the preferred embodiment and certain especially significant operating conditions have been set forth in detail, it should be understood that various modifications are readily apparent. In the preferred embodiment, the light-emitting diodes take the form of gallium arsenide phosphide LED's of the type more fully shown and described in assignee's U.S. Pat. No 3,576,099, issued Apr. 27, 1971, the disclosure of which is incorporated herein by reference. However, it is understood that the display can assume any one of several forms. For example, the optical display may be formed using such well known devices as miniature incandescent bulbs, other types of light-emitting diodes or the well known liquid crystals, as well as lesser known devices such as ferroelectric crystals or electroluminescent displays and others. If desired, the electrical signals may be connected through a suitable electromechanical transducer or motor to drive conventional watch hands.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

What is claimed and desired to be secured by United States Letters Patent is:

1. A solid state wristwatch comprising a source of constant frequency electrical signals, a plurality of electrooptical display devices, said display devices being physically arranged to display at least the seconds and minutes of time in digital form, and an integrated circuit formed on a single chip entirely of complementary symmetry MOS transistors electrically coupling said source to said display devices, said single chip integrated circuit including a divider for dividing down the frequency of the signals from said source and a single decoder coupling said divided signals to said display devices, a plurality of counting registers coupled to said divider and producing binary coded decimal signals, and means coupling said binary coded decimal signals to said decoder, said means coupling said binary coded decimal signals to said decoder comprising a plurality of selection gates.

2. A solid state wristwatch comprising a source of constant frequency electrical signals, a plurality of electrooptical display devices, said display devices being physically arranged to display at least the minutes and hours of time in digital form, and a single chip large-scale integrated circuit formed entirely of complementary symmetry MOS transistors electrically coupling said source to said display devices, said integrated circuit including a divider for dividing down the frequency of the signals from said source and a decoder coupling said divided signals to said display devices, and a strobe circuit coupled to said display devices for energizing said display devices in sequence at a rate sufficiently high to give the appearance of continuous energization.

3. A solid state wristwatch comprising a source of constant frequency electrical signals, a plurality of electrooptical display devices, said display devices being physically arranged to display at least the minutes and hours of time in digital form, and a single chip integrated circuit formed entirely of complementary symmetry MOS transistors electrically coupling said source to said display devices, said integrated circuit including a divider coupled to said source for dividing down the frequency of the signals from said source, a plurality of counting registers coupled to the output of said divider and producing binary coded decimal signals, a plurality of selection gates coupled to the outputs of said registers, a decoder coupling the output of said selection gates to said display devices, and a strobing circuit coupled to said selection gates whereby said gates are activated in sequence in accordance with the output of said strobing circuit.

4. A wristwatch according to claim 2 wherein the same ones of said electro-optical display devices display both minutes and seconds of time.

5. A wristwatch according to claim 4 wherein said electro-optical display devices include means coupled to said divider and physically arranged to decimal the hours of time in physical form.

6. A wristwatch according to claim 5 wherein said display devices comprise a plurality of stations formed by a seven bar segment array of electro-optical devices.

7. A wristwatch according to claim 6 wherein said hours display includes an hours tens station comprising a pair of commonly connected colinear electro-optical bar segments.

8. A wristwatch according to claim 6 wherein said electro-optical display devices comprise light-emitting diodes.

9. A wristwatch according to claim 2 wherein said constant frequency source comprise a crystal controlled oscillator.

10. A wristwatch according to claim 2 wherein said strobe circuit forms part of said large-scale integrated circuit means.

11. A wristwatch according to claim 10 wherein said strobe circuit is coupled to said divider to receive signals having a frequency of at least 128 Hz from said divider.

12. A wristwatch according to claim 11 including a photosensor on the face of said timepiece, said photosensor being coupled between said divider and said strobe circuit whereby the duty cycle of the signal from said strobe circuit varies in accordance with the light incident on the face of said timepiece.

13. A wristwatch according to claim 3 wherein said strobing circuit has a first set of outputs coupled to said selection gates and a second set of outputs coupled to said display devices.

14. A wristwatch according to claim 3 wherein said display devices comprise four stations, two of said stations forming both a minutes and seconds display, the other two stations forming an hours display.

15. A wristwatch according to claim 3 including a plurality of electrical information inputs coupled to said decoder for introducing special information into said display from externally of said wristwatch.

16. A wristwatch according to claim 3 wherein said registers comprise a seconds register, a minutes register and an hours register, and an electrical carry output terminal coupled to said hours register to provide a carryout signal from said wristwatch.

17. A wristwatch according to claim 3 including an information lockout terminal coupled to said strobing circuit for inhibiting the output from said registers to said decoder.

18. A wristwatch according to claim 3 including an optional electrical input terminal coupled to said strobing circuit for turning the hours and minutes display devices on all the time.