Abstract:
A semiconductor integrated circuit driven by an external power, comprises a change unit whose state changes with lapse of time without the external power, an output unit configured to output a signal in response to an instruction issued when the external power is supplied, the signal indicating a change of the state of the change unit, and an execution unit configured to execute a process in response to the signal. Therefore, the circuit is capable of utilizing time-point/time-period information even if they are not supplied with power.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2002-373563, filed Dec. 25, 2002, the entire contents of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a semiconductor integrated circuit, a semiconductor integrated circuit module and an information apparatus, which utilize information concerning a time period and point. 
   2. Description of the Related Art 
   Semiconductor integrated circuits for use in information apparatuses are driven by electric power. Most information apparatuses are connected to an AC power supply via a cable, or to a battery, and power is supplied therefrom to semiconductor integrated circuits incorporated in the apparatuses. 
   On the other hand, some information apparatuses acquire power from electromagnetic waves, utilizing electromagnetic induction. This power is supplied to the semiconductor circuits incorporated therein to operate them. In light of the physical conformation or use, these information apparatuses are suitable for radio tags, non-contact IC cards, etc. that cannot incorporate batteries. 
   Radio tags and non-contact IC cards are equipped with an IC chip and antenna and no batteries. They are operated by an electromotive force that results from electromagnetic induction based on Fleming&#39;s law. Non-contact IC cards are of the same shape as standard magnetic cash cards. On the other hand, radio tags have various shapes. Non-contact IC cards or radio tags, called “a adjacent/vicinity type”, are accessible at a distance of approx. 1 m at maximum. Non-contact IC cards are standardized by ISO/IEC14443 (adjacent type) and ISO/IEC15693 (vicinity type). Most radio tags are based on these standards (see, for example, Jpn. Pat. Appln. KOKAI Publication No. 10-135882). 
   Typical systems utilizing such an information apparatus as the above are, for example, a shoplifting prevention system, in which a gate that generates electromagnetic waves is provided at the exit of a shop, and radio tags are attached to exhibited articles, or an automatic ticket gate system, in which automatic ticket checkers that generate electromagnetic waves are provided at ticket gates, and non-contact IC cards are used as commuter passes. 
   Information apparatuses utilizing electromagnetic induction by electromagnetic waves are not intended to always receive electromagnetic waves, but receive them only when necessary (only when they are used). In other words, the information apparatuses are not supplied with power when they are not used. 
   To control, for example, the period of use of an information apparatus that is supplied with power only when it is used, there were some methods, such as a method for managing the period of use at an apparatus that supplies electromagnetic waves, or a method for supplying time data together with electromagnetic waves to an information apparatus to enable it to use the time data. In both methods, the information apparatus depends on the power supply apparatus, which means that users of the power supply apparatus can illegally use the information apparatus by a simple modification of the power supply apparatus. Therefore, there is a need for a highly reliable semiconductor integrated circuit that enables information apparatuses to acquire correct time data used for control without depending on power supply apparatuses. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention has been developed in light of the above circumstances, and aims to provide a semiconductor integrated circuit, a semiconductor integrated circuit module and an information apparatus capable of utilizing time-point/time-period information even if they are not supplied with power. 
   According to a first aspect of the invention, there is provided a semiconductor integrated circuit driven by an external power, comprising: a change unit whose state changes with lapse of time without the external power; an output unit configured to output a signal in response to an instruction issued when the external power is supplied, the signal indicating a change of the state of the change unit; and an execution unit configured to execute a process in response to the signal. 
   According to a second aspect of the invention, there is provided a semiconductor integrated circuit module comprising: 
   a semiconductor integrated unit including:
         a power supply which acquires a current from an antenna, and rectifies and smoothes a acquired current, and supplying, as a power, a rectified and smoothed current to an interior of the semiconductor integrated unit;   a change unit whose state changes with lapse of time without the power;   an output unit configured to output a signal in response to an instruction issued when the power supply supplies the power, the signal indicating a change of the state of the change unit; and   an execution unit configured to execute a process in response to the signal;       

   a sealing material which seals the semiconductor integrated unit; and 
   an antenna terminal which connects the power supply to the antenna, the antenna terminal being exposed on an outer surface of the sealing material. 
   According to a third aspect of the invention, there is provided an information apparatus comprising: an antenna which acquires a current induced by electromagnetic induction; a power supply connected to the antenna, the power supply acquiring a current, rectifying and smoothing the acquired current, and supplying, as a power, a rectified and smoothed current to an interior of the information apparatus; a change unit whose state changes with lapse of time without the power from the power supply; an output unit configured to output a signal in response to an instruction issued when the power supply supplies the power, the signal indicating a change of the state of the change unit; and an execution unit configured to execute a process in response to the signal. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       FIG. 1  illustrates the whole system for which an information apparatus according to an embodiment of the invention is used; 
       FIGS. 2A ,  2 B,  2 C and  2 D illustrate an example of a non-contact IC card  20 ; 
       FIG. 3  is a block diagram illustrating the internal function blocks of an IC chip  22  incorporated in the IC card  20 ; 
       FIG. 4  is a block diagram illustrating the basic concept of a timer  37 ; 
       FIG. 5  shows a first example that realizes the basic concept of the timer  37 ; 
       FIG. 6  illustrates changes with lapse of time in the state of a timer  37 - 1 ; 
       FIG. 7  is a graph illustrating the relationship between the time and the output signal of the timer  37 - 1 ; 
       FIG. 8  is a second example that realizes the basic concept of the timer  37 ; 
       FIG. 9  is a third example that realizes the basic concept of the timer  37 ; 
       FIGS. 10A and 10B  show connection examples of timer  37  and control circuit  34 ; 
       FIG. 11  is a schematic flowchart illustrating an operation of the control circuit  34 ; 
       FIG. 12  illustrates a table  91 ; 
       FIG. 13  is a schematic flowchart illustrating another operation of the control circuit  34 ; 
       FIG. 14  is a block diagram illustrating the functions of an IC chip  22 ′ that is a modification of the IC chip  22 ; 
       FIG. 15  is a schematic flowchart illustrating another operation of a control circuit  93 ; and 
       FIG. 16  is a graph illustrating the characteristics, i.e., changes in state with lapse of time, of timers  37  and  92 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   An embodiment of the invention will be described in detail with reference to the accompanying drawings. 
     FIG. 1  shows the whole system to which an information apparatus according to an embodiment of the invention is applied. The information apparatus is, for example, a radio tag or non-contact IC card. In this text, only non-contact IC card examples will be described. 
   The system shown in  FIG. 1  comprises an IC card reader/writer  10  connected to a server computer (not shown), and a non-contact IC card  20 . When the non-contact IC card  20  is located close to the IC card reader/writer  10 , a current is generated in the IC card  20  by electromagnetic induction, i.e., by electromagnetic waves supplied from the reader/writer  10 . Thus, the non-contact IC card  20  is operable without a battery. 
   As shown in  FIG. 1 , the IC card reader/writer  10  comprises a transmission unit  11  for modulating a command transmitted superposed on electromagnetic waves, a transmission loop antenna  12  connected to the transmission unit  11  for generating, to the outside, electromagnetic waves with a command superposed thereon, a reception loop antenna  13  for receiving electromagnetic waves with data superposed thereon from the outside, and a receiving unit  14  for decoding the data superposed on the electromagnetic waves received by the reception loop antenna  13 , and transferring the decoded data to a server. 
   The non-contact IC card  20  comprises a transmission/reception loop antenna  21  for receiving electromagnetic waves supplied from the transmission loop antenna  12  of the IC card reader/writer  10 , and transmitting electromagnetic waves to the reception loop antenna  13 , and an IC chip  22  connected to the transmission/reception loop antenna  21 . The IC chip  22  will be described later in more detail. 
     FIG. 2A  shows the outward appearance of an example of the non-contact IC card  20 ,  FIG. 2B  shows the internal structure of the card,  FIG. 2C  is a side view of an IC module incorporated in the card, and  FIG. 2D  is a rear view of the IC module. The non-contact IC card  20  is generally a thin card. Therefore, the IC chip  22 , which is obtained by forming a circuit block, described later, integral with a chip as one body, is sealed in a sealing material  23  (except for the lines led from the block and connected to the transmission/reception loop antenna  21 ), thereby providing an IC module protected from, for example, external forces. The lines connected to the transmission/reception loop antenna  21  extend from two contacts  24  exposed on the outer surface of the IC module. 
     FIG. 3  is a block diagram illustrating the internal function blocks of the IC chip  22 . 
   A rectifier circuit  31  rectifies the current generated by the transmission/reception loop antenna  21  when it receives electromagnetic waves. A smoothing circuit  32  smoothes the rectified current and supplies it to each element in the IC chip  22 . 
   A demodulation circuit  35  receives and demodulates the current generated by the transmission/reception loop antenna  21 , thereby acquiring the command supplied from the IC card reader/writer  10  and supplying it to a control circuit  34 . 
   A modulation circuit  26  modulates the data output from the control circuit  34  to enable it to be superposed on electromagnetic waves and to be generated to the outside. The resultant current is supplied to the transmission/reception antenna  21 , which, in turn, generates electromagnetic waves. 
   A memory  33  is a non-volatile semiconductor memory, EEPROM. 
   A timer  37  indicates whether or not a predetermined period of time has passed, and changes its state with lapse of time during time measurement without power. In other words, the timer changes its state even if the non-contact card  20  is sufficiently away from the IC card reader/writer  10  such that no current occurs. 
   The timer  37  will be described in detail. 
     FIG. 4  illustrates the basic concept of the timer  37 . The timer  37  comprises: a change unit  41 , the state of which changes with lapse of time without a power supply such as a battery; an input unit  42  for inputting a input signal to the change unit  41 ; and an output unit  43  for outputting an output signal changed relative to the input signal in accordance with the state of the change unit  41 . The state of the change unit  41  changes with lapse of time, and its changed state is used for measuring time. The input and output units  42  and  43  are used to confirm the state of the change unit  41 . 
     FIG. 5  shows a first example  37 - 1  that realizes the basic concept of the timer  37 . 
   The first timer example  37 - 1  comprises: a first layer having a source region  51 , drain region  52  and channel region  53  therebetween; a second layer provided on the first layer and formed of a tunnel insulation film  54 ; a third layer provided on the second layer and formed of a floating gate  55 ; a fourth layer provided on the third layer and formed of an insulation film  56 ; and a fifth layer provided on the fourth layer and formed of a control gate  57 . A source electrode  58  and drain electrode  59  are provided on the source and drain regions  51  and  52 , respectively. 
     FIG. 6  illustrates changes with lapse of time in the state of the timer  37 - 1 . In the figure, hatched circles indicate electrons, and white circles indicate positive holes. 
   State  1  is an initial state. In the timer  37 - 1 , a pre-process is performed, in which the control gate  57  applies a high electric field between the substrate boundary of the channel region  53  and the floating gate  55 , thereby injecting electrons from the channel into the floating gate  55  utilizing FN tunneling. At this time, positive holes gather at the substrate boundary of the channel region  53 , whereby a channel is formed on the substrate boundary between the source and drain regions  51  and  52 . 
   This pre-process may be performed when, for example, the semiconductor integrated circuit of the embodiment is manufactured, or when a device, such as a card, incorporating the semiconductor integrated circuit is issued or sold, or when the records in the device are updated. The device functions as an entrance ticket, commuter pass, one-day ticket or two-day limited express ticket. It is also assumed that the pre-process is performed periodically, for example, at 8 a.m. every day. Further, the pre-process may be performed when a product that contains the semiconductor integrated circuit requires maintenance work. 
   The electrons in the floating gate  55  gradually shift, by direct tunneling, to the substrate boundary, thereby reducing the level of the electric field at the substrate boundary in the channel region  53 , compared to the state  1 . State  2  is assumed at a time point T 1  a certain time period after the state  1 . State  3  is assumed at a time point T 2  a certain time period after the state  2 . Similarly, state  4  is assumed at a time point T 3  a certain time period after the state  3 . The circles indicated by the broken lines represent the shift of electrons made due to direct tunneling by the respective time points. In the state  4  at the time point T 3 , most electrons escape from the floating gate  55 , therefore the channel at the substrate boundary of the channel region  53  disappears. As a result, no signals are output. 
     FIG. 7  is a graph illustrating the relationship between the time and the output signal of the timer  37 - 1 . Direct tunneling occurs between time points T a  (=0) and T b , and lastly, the channel disappears, whereby the level of the output signal is reduced to the noise level. Since the timer  37 - 1  supplies an output signal corresponding to a change in level between T a  (=0) and T b  (=the time when the output signal level reaches the noise level), the side for receiving the output signal can determine whether or not a predetermined time period has elapsed, or can determine a specific time point (e.g. T 1 , T 2  or T 3  shown in  FIG. 7 ) a predetermined time period after the initial state if the relationship between the state of the timer  37 - 1  and the level of the output signal is always clear. The time points T 1 , T 2  and T 3  correspond to the states  2 ,  3  and  4  in  FIG. 6 . 
     FIG. 8  is a second example  37 - 2  that realizes the basic concept of the timer  37  of  FIG. 4 . The timer  37 - 2  comprises: a first layer having a source region  61 , drain region  62  and channel region  63  therebetween; a second layer provided on the first layer and formed of a tunnel insulation film  64 ; a third layer provided on the second layer and formed of a gate  65 ; and a PN junction provided on the third layer for controlling a leak current. A source electrode  68  and drain electrode  69  are provided on the source and drain regions  61  and  62 , respectively. 
   The change in the state of the timer  37 - 2  with lapse of time is similar to that of the timer  37 - 1 , although in the former, current leakage occurs in a PN junction, and in the latter, direct tunneling occurs. Therefore, no description is given of the change in the state of the timer  37 - 2  with lapse of time. 
     FIG. 9  is a third example  37 - 3  that realizes the basic concept of the timer  37  of  FIG. 4 . The timer  37 - 3  comprises: a first layer having a source region  71 , drain region  72  and channel region  73  therebetween; a second layer provided on the first layer and formed of a tunnel insulation film  74 ; a third layer provided on the second layer and formed of a gate  75 ; and a Schottky junction  76  provided on the third layer for controlling a leak current. A source electrode  78  and drain electrode  79  are provided on the source and drain regions  71  and  72 , respectively. 
   The change in the state of the timer  37 - 3  with lapse of time is similar to that of the timer  37 - 1 , although in the former, current leakage occurs in a Schottky junction, and in the latter, direct tunneling occurs. Therefore, no description is given of the change in the state of the timer  37 - 3  with lapse of time. 
   As described above, a pre-process for forming a channel is needed before time measurement is started by the timer  37  (hereinafter, the timer  37  represents the timers  37 - 1 ,  37 - 2  and  37 - 3 ). If, however, anyone can perform the pre-process, a security risk arises. To avoid this, authentication to confirm as to whether or not the IC card reader/writer  10  is legal, which is often performed for standard IC cards, may be employed. In this case, only when the reader/writer  10  is determined to be legal, the pre-process is performed and time measurement is started. 
   The above-described timer  37  is connected to the control circuit  34 .  FIGS. 10A and 10B  show examples of connection of the timer  37  and circuit  34 . 
   In the case of  FIG. 10A , when the smoothing circuit  32  supplies power to the timer  37 , a voltage occurs between the opposite ends of the timer  37 . A power supply terminal  81  is connected to the source electrode  58 ,  68 ,  78  of the timer  37  via a switch element  83 , while a GND terminal  82  is connected to the drain electrode  59 ,  69 ,  79  via an ampere meter  84 . 
   The switch element  83  is connected to an ON/OFF (enable) signal line led from the control circuit  34 , and is turned on when an ON signal is supplied. The ampere meter  84  is connected to output a current value to the control circuit  34 . 
   When the control circuit  34  turns on the switch element  83  to confirm the state of the timer  37  during the operation of the IC chip  22 , a predetermined voltage is applied between the power supply terminal  81  and GND terminal  82 , whereby the ampere meter  84  measures the current flowing through the timer  37  and outputs the measurement result to the control circuit  34 . As a result, the control circuit  34  detects the state of the timer  37 . 
   In the above connection example, a single timer  37  is employed. However, a plurality of timers  37  may be employed. The change with lapse of time in the state of the change unit  41  of one timer  37  may be the same as or different from that of the change unit  41  of another timer  37 , according to purpose. Referring now to  FIG. 10B , a description will be given of the case where the timers  37  show the same change in state with lapse of time. In this example, a plurality of timers  37  similar to that shown in  FIG. 10A  are arranged parallel to each other, the current values output from them are input to an averaging circuit  85 , and the averaged current is output from the circuit  85  to the control circuit  34 . The ON/OFF (enable) signal line led from the control circuit  34  is connected to the respective switch elements  83  to make them be commonly controlled by the control circuit  34 . In this example, even if the change units  41  of the timers  37  exhibit some different changes in state with lapse of time, their average value enables a stable timer to be realized. Further, if change units  41  that show different changes in state with lapse of time are employed (this case is not shown), various types of time information can be acquired, for example. 
   The control circuit  34  is connected to the demodulation circuit  35  to receive therefrom a demodulated command, and is also connected to the modulation circuit  36  to output thereto a process result based on the command. Further, the control circuit  34  is connected to the timer  37  as shown in the connection example. A command supplied to the control circuit  34  is, for example, a command to read an ID dedicated to the IC chip  22  (or IC card  20 ), from which the chip (or card) can be directly identified, or a command to write information, such as the name of a station from which a train or the like has been utilized. 
   The control circuit  34  incorporates a CPU, ROM and RAM, which are not shown. The CPU operates in accordance with a program prestored in the ROM, using the RAM as a work memory. Referring to  FIG. 11 , the operation of the control circuit  34  will be described roughly. 
   Firstly, the control circuit  34  receives a command from the demodulation circuit  35  (S 101 ). Subsequently, the control circuit  34  refers to the timer  37  (S 102 ). Concretely, an ON signal to input to the timer  37  to acquire a current value therefrom. The control circuit  34  determines from the current value whether or not the command should be processed (S 103 ). The determination at the step S 103  is, for example, as to whether or not the current value (level) is equal to (or less than) the noise level shown in  FIG. 7 . If the current level is equal to the noise level, this means that a predetermined time period has passed, while if it is higher than the noise level, it means that the predetermined time period (T b  in  FIG. 7 ) has not yet passed. 
   If it is determined that the command should be processed, the command is processed (S 104 ). The control circuit  34  supplies the process result to the modulation circuit  36  (S 105 ). If it is determined that the command should not be processed, another predetermined process (for example, a process for informing that the card has expired) is performed, or no process is performed (S 106 ). The step S 106  indicates that a desired process is not performed. 
   The above-described operation of the control circuit  34  is just one example. In another example, described referring to  FIG. 7 , in which the relationship between the state of the timer  37  and the level of the output signal is clearly followed, the time period elapsing from the initial state can be acquired. Therefore, a command can be processed using time information. In this case, if a time information table  91  that stores current value (output signal level) ranges in relation to time information, as shown in  FIG. 12 , is held in the ROM of the control circuit  34 , time information corresponding to each current value can be utilized for processing a command. This will be described in more detail with reference to the flowchart of  FIG. 13 . 
   Firstly, the control circuit  34  receives a command from the demodulation circuit  35  (S 201 ). Subsequently, the control circuit  34  refers to the timer  37  to acquire a current value (S 202 ). After that, the control circuit  34  acquires time data corresponding to the acquired current value, from the time information table  91  in the ROM (S 203 ). In accordance with the program stored in the RAM, the control circuit  34  processes the command supplied from the demodulation circuit  35  (S 204 ). This process is assumed to include a process utilizing the acquired time data. The control circuit  34  transmits the process result to the modulation circuit  36  (S 205 ). 
   If the control circuit  34  is made to operate as described above, it can utilize time data. Although the embodiment utilizes the time information table  91  to acquire time data, the embodiment of the invention is not limited to this. For example, a function f(c) may be stored, which uses, as a variable, a current value (c) that varies as shown in the graph of  FIG. 7 , thereby acquiring time data by calculation using the function f(c). 
   Further, although in the embodiment, attention has been paid to the use of only time information, the flowcharts of  FIGS. 11 and 13  may be combined so that both term and time information can be used for command processing. 
   As described above in detail, if the IC chip  22  of the embodiment is applied to, for example, a non-contact IC card or radio tag that cannot always be supplied with power, it performs command processing when it is supplied with power, and the timer employed in the chip continues to change its state until a predetermined time period passes even when the chip is supplied with no power. On the basis of the time data obtained from the timer and indicative of a predetermined elapsed time period, a determination as to whether or not command processing should be performed, or other data processes can be performed, is made. In other words, the embodiment of the invention can provide an IC chip that incorporates a semiconductor capable of measuring time even if no power is supplied thereto, and capable of using the measured time-period/time-point when power is supplied. The IC chip with the timer function does not need a power supply line or GND line to be connected to an external power supply, therefore can be provided in the form of a sealed module with only an antenna contact exposed to the outside, like the conventional non-contact IC cards that do not need batteries. 
   A modification of the IC chip  22  will now be described. 
     FIG. 14  is a block diagram illustrating the functions of an IC chip  22 ′ that is a modification of the IC chip  22 . The IC chip  22 ′ differs from the above-described IC chip  22  in that the former incorporates a timer  92  as well as the timer  37 . The timer  92  has the same structure as the timer  37  but shows different changes in state with lapse of time. Different changes in state with lapse of time can be realized by, for example, modifying the first example of  FIG. 5  such that the degree of tunneling in the tunnel insulation film  54  is different from that in the first example, or such that the number of electrons accumulated in the floating gate  55  in the initial state is different. 
   A control circuit  93  incorporated in the IC chip  22 ′ additionally incorporates a connection unit used to refer to the timer  92 , and two timers similar to that shown in  FIG. 10A  are employed. These points differ from the IC chip  22 . In addition, the program stored in the ROM is changed. 
   Specifically, the program is changed to perform more accurate time control using the two timers  37  and  92 .  FIG. 15  illustrates another operation of the control circuit  93  based on the changed program. In the following description, it is assumed that the timer  92  reaches the noise level much earlier than the timer  37 , and term information is utilized instead of time-point information. 
   Firstly, the control circuit  93  receives a command from the demodulation circuit  35  (S 301 ). Subsequently, the control circuit  93  refers to the timer  92  (S 302 ). The control circuit  93  determines whether or not the current value acquired from the timer  92  is equal to (or less than) the noise level (S 303 ). If the current level is equal to the noise level, the control circuit  93  refers to the timer  37  (S 304 ). The control circuit  93  determines whether or not the current value acquired from the timer  37  is equal to (or less than) the noise level (S 305 ). If the current level is higher than the noise level, the control circuit  93  processes the command (S 306 ), and outputs the process result to the modulation circuit  36  (S 307 ). 
   If it is determined at the step S 303  that the current level is higher than the noise level, or if it is determined at the step S 305  that the current level is equal to or less than the noise level, it is determined that the command-processing allowable term of the card is exceeded, with the result that another predetermined process (for example, a process for informing that the card has expired) is performed, or no process is performed (S 308 ). 
     FIG. 16  is a graph illustrating the characteristics (i.e., changes in state with lapse of time) of the timers  37  and  92  that are related to the above-described time management. As shown, when the timer  92  has measured a predetermined term (Ts), a state in which command processing can be performed is assumed. After that, until the timer  37  has measured a predetermined term, the command-processing enabled state is continued. When the timer  37  has measured the predetermined term (Tb), a state in which command processing cannot be performed is assumed. 
   In this modification, it is determined, using the two timers  37  and  92 , whether or not a command from the IC card reader/writer  10  should be processed. However, this may be modified such that two command-processing programs are stored in the ROM of the control circuit  92  for each command supplied from the IC card reader/writer  10 , and one of the two program that corresponds to the term including the command receiving time is executed. This enables various types of control. 
   The IC chip  22 ′ according to the modification of the embodiment provides, as well as the above-mentioned advantages of the embodiment, the advantage that when a predetermined valid term is set, its start time can also be set. 
   Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.