Abstract:
A reader/writer (RW) requires identification information pieces of respective plural IC cards (A, B, C). The plural IC cards return the respective identification information pieces in response to the requirement by the reader/writer. Logical addresses are assigned to some IC cards among the plural IC cards respectively to cause the reader/writer to select them in response to the return of the identification information pieces by the plural IC cards. The IC cards selected by the reader/writer are controlled. The reader/writer cancels the assignment of the logical address to one of the selected IC cards. The logical address, the assignment of which has been canceled by the reader/writer, is assigned to an IC card among the plural IC cards to which any logical address has not been assigned yet. The IC card to which the logical address has just been assigned is controlled.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a system for controlling contactless IC (integrated circuit) cards. This invention also relates to a method of controlling contactless IC cards. 
     2. Description of the Related Art 
     In a prior-art contact IC card control system, IC cards communicate with readers/writers when being inserted thereinto. In each of the readers/writers, the type of an IC card placed thereinto is detected as follows. When the IC card is reset, for example, when the IC card is subjected to a power-on resetting process, the IC card transmits a reset notice to a reader/writer. The reset notice contains information of the type of the IC card. The reader/writer identifies or detects the type of the IC card in response to the reset notice transmitted from the IC card. Then, the reader/writer implements the following processes related to the identified IC card. First, the reader/writer assigns a logical address to the IC card in accordance with the identified type thereof. Second, the reader/writer controls the reading and the writing of information from and into the IC card in response to the logical address. The assignment of the logical address to the IC card is canceled when the IC card is reset by turning off the power supply. 
     In a contactless IC card control system, a reader/writer has a communication service area (a communication coverage). The reader/writer can communicate with an IC card or IC cards in the communication service area by radio. 
     In a conceivable contactless IC card control system, a reader/writer assigns different logical addresses to respective IC cards in its communication service area. The reader/writer feeds power to the IC cards by radio. When the power supply of the reader/writer is turned off, power feed to all the IC cards is suspended so that the assignment of the logical addresses thereto is canceled at once. Accordingly, in the conceivable contactless IC card control system, it is difficult to cancel the assignment of the logical address to one of the IC cards. In addition, it is difficult to control IC cards, the number of which exceeds the number of usable logical addresses. 
     Generally, as the number of different logical addresses increases, the number of bits representing each logical address increases. An increase in the number of address-representing bits is disadvantageous to signal processing which includes address processing. 
     SUMMARY OF THE INVENTION 
     It is a first object of this invention to provide a system for controlling contactless IC (integrated circuit) cards which can cancel the assignment of a logical address to one of the IC cards. 
     It is a second object of this invention to provide a method of controlling contactless IC (integrated circuit) cards which can cancel the assignment of a logical address to one of the IC cards. 
     It is a third object of this invention to provide a system for controlling contactless IC (integrated circuit) cards, the number of which exceeds the number of usable logical addresses. 
     It is a fourth object of this invention to provide a method of controlling contactless IC (integrated circuit) cards, the number of which exceeds the number of usable logical addresses. 
     A first aspect of this invention provides a contactless IC card control system comprising first means ( 200 ) for causing a reader/writer (RW) to require identification information pieces of respective plural IC cards (A, B, C); second means ( 310 ) for causing the plural IC cards to return the respective identification information pieces in response to the requirement by the first means; third means ( 212 ,  213 ,  220 ,  230 ,  320 ) for assigning logical addresses to some IC cards among the plural IC cards respectively to cause the reader/writer to select the some IC cards among the plural IC cards in response to the return of the identification information pieces by the second means; fourth means ( 240 ,  241 ,  250 ,  340 ,  370 ) for controlling the some IC cards selected by the reader/writer; fifth means ( 260 ,  261 ,  360 ) for causing the reader/writer to cancel the assignment of the logical address to one of the some IC cards; sixth means ( 262 ,  263 ,  320 ,  330 ) for assigning the logical address, the assignment of which has been canceled by the fifth means, to an IC card among the plural IC cards to which any logical address has not been assigned yet; and seventh means ( 264 ,  340 ,  370 ) for controlling the IC card to which the logical address has been assigned by the sixth means. 
     A second aspect of this invention provides a method of controlling contactless IC cards which comprises the steps of causing a reader/writer (RW) to require identification information pieces of respective plural IC cards (A, B, C); causing the plural IC cards to return the respective identification information pieces in response to the requirement by the reader/writer; assigning logical addresses to some IC cards among the plural IC cards respectively to cause the reader/writer to select the some IC cards among the plural IC cards in response to the return of the identification information pieces by the plural IC cards; controlling the some IC cards selected by the reader/writer; causing the reader/writer to cancel the assignment of the logical address to one of the some IC cards; assigning the logical address, the assignment of which has been canceled by the reader/writer, to an IC card among the plural IC cards to which any logical address has not been assigned yet; and controlling the IC card to which the logical address has been assigned by the immediately-preceding step. 
     A third aspect of this invention provides a contactless IC card control system comprising first means for assigning a first logical address to a first IC card; second means for assigning a second logical address to a second IC card, the second logical address differing from the first logical address, the second IC card differing from the first IC card; third means for canceling the assignment of the first logical address to the first IC card while maintaining the assignment of the second logical address to the second IC card; and fourth means for, after the assignment of the first logical address to the first IC card is canceled by the third means, assigning the first logical address to a third IC card which differs from the first and second IC cards. 
     A fourth aspect of this invention provides a contactless IC card control system comprising first means for assigning a first logical address to a first IC card; second means for assigning a second logical address to a second IC card, the second logical address differing from the first logical address, the second IC card differing from the first IC card; third means for controlling the first IC card in response to the first logical address; fourth means for, after the third means controls the first IC card, canceling the assignment of the first logical address to the first IC card while maintaining the assignment of the second logical address to the second IC card; and fifth means for, after the assignment of the first logical address to the first IC card is canceled by the fourth means, assigning the first logical address to a third IC card which differs from the first and second IC cards. 
     A fifth aspect of this invention is based on the fourth aspect thereof, and provides a contactless IC card control system further comprising sixth means for, after the fifth means assigns the first logical address to the third IC card, controlling the third IC card in response to the first logical address. 
     A sixth aspect of this invention is based on the fourth aspect thereof, and provides a contactless IC card control system further comprising sixth means for controlling the second IC card in response to the second logical address. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagram of a contactless IC card control system according to an embodiment of this invention. 
     FIG. 2 is a block diagram of an electrical portion of a reader/writer in FIG.  1 . 
     FIG. 3 is a block diagram of an electrical portion of an IC card in FIG.  1 . 
     FIGS. 4 and 5 are a flowchart of a program for a microcomputer in the reader/writer of FIG.  2 . 
     FIG. 6 is a flowchart of a program for a microcomputer in the IC card of FIG.  3 . 
     FIGS. 7 and 8 are diagrams of signals transmitted between the reader/writer and IC cards in FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to FIG. 1, a contactless IC card control system includes a reader/writer RW provided on, for example, a telephone set. A given communication service area (a given communication coverage) provided by the reader/writer RW extends therefrom. Under exemplary conditions shown in FIG. 1, three IC cards “A”, “B”, and “C” are placed in the communication service area. For example, the IC cards “A”, “B”, and “C” are prepaid cards for using a telephone set. The reader/writer RW can communicate with the IC cards “A”, “B”, and “C” by radio. 
     As shown in FIG. 2, the reader/writer RW includes a microcomputer  10 , a memory  20 , a modulation circuit  30 , an antenna  40 , and a demodulation circuit  50 . The modulation circuit  30  and the demodulation circuit  50  are connected to the antenna  40 . The microcomputer  10  is connected to the memory  20 , the modulation circuit  30 , and the demodulation circuit  50 . The microcomputer  10  is electrically connected to, for example, a telephone set. 
     The microcomputer  10  includes a combination of an input/output port, a CPU, a ROM, and a RAM. The microcomputer  10  operates in accordance with a program stored in the ROM. The program has a first segment for implementing radio communications with each IC card placed in the communication service area. The program has a second segment for detecting or identifying the type of each IC card. The program has a third segment for assigning a logical address to each IC card. The program has a fourth segment for canceling the assignment of a logical address to a designated IC card. The program has a fifth segment for controlling each IC card. 
     The memory  20  is previously loaded with data representing at least two different logical addresses (that is, a logical address “1” and a logical address “2”). The memory  20  can be accessed by the microcomputer  10 . 
     The modulation circuit  30  receives output data (a baseband signal) from the microcomputer  10 . The modulation circuit  30  subjects the output data from the microcomputer  10  to modulation, thereby converting the data (the baseband signal) into a radio signal. The modulation circuit  30  outputs the radio signal to the antenna  40 . The radio signal is radiated by the antenna  40 . 
     A radio signal coming from each IC card in the communication service area is received by the antenna  40 . The received radio signal is fed from the antenna  40  to the demodulation circuit  50 . The demodulation circuit  50  subjects the received radio signal to demodulation, thereby recovering baseband data therefrom. The demodulation circuit  50  outputs the recovered data to the microcomputer  10 . 
     The IC cards “A”, “B”, and “C” are similar in structure. Accordingly, only the structure of the IC card “A” will be explained in detail. As shown in FIG. 3, the IC card “A” includes an antenna  60 , a power supply circuit  70 , a demodulation circuit  80 , a memory  90 , a microcomputer  100 , and a modulation circuit  110 . The antenna  60  is connected to the power supply circuit  70 , the demodulation circuit  80 , and the modulation circuit  110 . The microcomputer  100  is connected to the demodulation circuit  80 , the memory  90 , and the modulation circuit  110 . 
     A radio signal coming from the reader/writer RW is received by the antenna  60 . The received radio signal is fed from the antenna  60  to the power supply circuit  70  and the demodulation circuit  80 . The power supply circuit  70  generates DC power from the received radio signal, and stores the generated DC power. In addition, the power supply circuit  70  feeds the DC power to the demodulation circuit  80 , the memory  90 , the microcomputer  100 , and the modulation circuit  110  to activate them. 
     The demodulation circuit  80  subjects the received radio signal to demodulation, thereby recovering baseband data therefrom. The demodulation circuit  80  outputs the recovered data to the microcomputer  100 . 
     The memory  90  is previously loaded with IC-card identification data or IC-card identification information (IC-card ID information). Specifically, the IC-card ID information includes data representing an ID code word corresponding to a type of the related IC card (the IC card “A”), and data representing parameters of the related IC card (the IC card “A”). The memory  90  can be accessed by the microcomputer  100 . 
     The microcomputer  100  includes a combination of an input/output port, a CPU, a ROM, and a RAM. The microcomputer  100  operates in accordance with a program stored in the ROM. The program has a segment for implementing radio communications with the reader/writer RW. 
     The modulation circuit  110  receives output data (a baseband signal) from the microcomputer  100 . The modulation circuit  110  subjects the output data from the microcomputer  100  to modulation, thereby converting the data (the baseband signal) into a radio signal. The modulation circuit  110  outputs the radio signal to the antenna  60 . The radio signal is radiated by the antenna  60 . 
     The IC card “B” is similar to the IC card “A” except that the memory  90  in the IC card “B” stores data representing an ID code word corresponding to a type of the IC card “B”, and data representing parameters of the IC card “B”. The IC card “C” is similar to the IC card “A” except that the memory  90  in the IC card “C” stores data representing an ID code word corresponding to a type of the IC card “C”, and data representing parameters of the IC card “C”. 
     The program in the microcomputer  100  of the IC card “B” is similar to that in the microcomputer  100  of the IC card “A”. In addition, the program in the microcomputer  100  of the IC card “C” is similar to that in the microcomputer  100  of the IC card “A”. 
     The contactless IC card control system operates as follows. It is assumed that as shown in FIG. 1, the IC cards “A”, “B”, and “C” exist in the communication service area provided by the reader/writer RW. 
     In the reader/writer RW, the microcomputer  10  outputs a signal Drw (see FIG. 7) of a requirement for IC-card ID information to the modulation circuit  30 . The modulation circuit  30  converts the ID information requirement signal Drw into a corresponding command radio signal referred to as a first command radio signal. The modulation circuit  30  outputs the first command radio signal to the antenna  40 . 
     The first command radio signal is radiated by the antenna  40 , being transmitted from the reader/writer RW to the IC cards “A”, “B”, and “C”. 
     In each of the IC cards “A”, “B”, and “C”, the first command radio signal is received by the antenna  60 . The received first command radio signal is fed from the antenna  60  to the demodulation circuit  80 . The demodulation circuit  80  recovers the ID information requirement signal Drw from the received first command radio signal. The demodulation circuit  80  outputs the recovered ID information requirement signal Drw to the microcomputer  100 . 
     In each of the IC cards “A”, “B”, and “C”, the microcomputer  100  reads out the ID data from the memory  90  in response to the ID information requirement signal Drw, and generates an answer signal Da, Db, or Dc (see FIG. 7) from the readout data. The microcomputer  100  outputs the answer signal Da, Db, or Dc (see FIG. 7) to the modulation circuit  110 . The answer signal Da, Db, or Dc contains the ID information of the related IC card. 
     Specifically, the answer signal Da outputted from the microcomputer  100  in the IC card “A” represents the ID code word corresponding to the IC card “A”. The answer signal Db outputted from the microcomputer  100  in the IC card “B” represents the ID code word corresponding to the IC card “B”. The answer signal Dc outputted from the microcomputer  100  in the IC card “C” represents the ID code word corresponding to the IC card “C”. 
     In the IC card “A”, the modulation circuit  110  converts the ID information answer signal Da into a corresponding radio answer signal RSa. The modulation circuit  110  feeds the radio answer signal RSa to the antenna  60 . The antenna  60  radiates and transmits the radio answer signal RSa. 
     In the IC card “B”, the modulation circuit  110  converts the ID information answer signal Db into a corresponding radio answer signal RSb. The modulation circuit  110  feeds the radio answer signal RSb to the antenna  60 . The antenna  60  radiates and transmits the radio answer signal RSb. 
     In the IC card “C”, the modulation circuit  110  converts the ID information answer signal Dc into a corresponding radio answer signal RSc. The modulation circuit  110  feeds the radio answer signal RSc to the antenna  60 . The antenna  60  radiates and transmits the radio answer signal RSc. 
     The antenna  40  in the reader/writer RW receives the radio answer signals RSa, RSb, and RSc from the IC cards “A”, “B”, and “C”. It is assumed that the radio answer signals RSa, RSb, and RSc are sequentially received by the reader/writer RW in that order. In the reader/writer RW, the received radio answer signals RSa, RSb, and RSc are fed from the antenna  40  to the demodulation circuit  50 . The demodulation circuit  50  recovers the ID information answer signals Da, Db, and Dc from the radio answer signals RSa, RSb, and RSc, respectively. The demodulation circuit  50  outputs the recovered ID information answer signals Da, Db, and Dc to the microcomputer  10 . In response to the recovered ID information answer signals Da, Db, and Dc, the microcomputer decides that IC cards are present in the communication service area, and answers to the ID information requirement have come therefrom. The recovered ID information answer signals Da, Db, and Dc represent the ID code words of the IC cards “A”, “B”, and “C”, respectively. Accordingly, the demodulation circuit  50  informs the microcomputer  10  of the recovered ID code words of the IC cards “A”, “B”, and “C”. The microcomputer  110  sets flags for the respective recovered ID code words. The microcomputer  10  uses each of the recovered ID code words as IC-card ID information. The microcomputer  10  writes signals (data) of the recovered ID code words into the memory  20  as IC-card ID information. 
     Subsequently, the microcomputer  10  in the reader/writer RW assigns the logical addresses “1” and “2” to the IC cards “A” and “B” as follows. The microcomputer  10  reads out the data from the memory  20  which represents the logical address “1” and the ID code word (the ID information) of the IC card “A”. The microcomputer  10  generates a selection requirement signal Srwa for the IC card “A” in response to the readout data. As shown in FIG. 7, the selection requirement signal Srwa has a sequence of a selection command, the logical address “1”, and the ID information of the IC card “A”. The microcomputer  10  outputs the selection requirement signal Srwa to the modulation circuit  30 . The modulation circuit  30  converts the selection requirement signal Srwa into a corresponding command radio signal referred to as a second command radio signal. The modulation circuit  30  outputs the second command radio signal to the antenna  40 . The second command radio signal is radiated by the antenna  40 , being transmitted from the reader/writer RW. 
     In the IC card “A”, the second command radio signal is received by the antenna  60 . The received second command radio signal is fed from the antenna  60  to the demodulation circuit  80 . The demodulation circuit  80  recovers the selection requirement signal Srwa from the received second command radio signal. The demodulation circuit  80  outputs the recovered selection requirement signal Srwa to the microcomputer  100 . The microcomputer  100  detects that the recovered selection requirement signal Srwa is directed to the IC card “A” on the basis of the ID information in the recovered selection requirement signal Srwa. In addition, the microcomputer  100  decides, from the recovered selection requirement signal Srwa, that the logical address “1” is assigned to the related IC card (the IC card “A”). The microcomputer  100  generates data representing that the logical address “1” is assigned to the related IC card (the IC card “A”). The microcomputer  100  writes the generated data into the memory  90 . Furthermore, the microcomputer  100  generates an assignment answer signal Sa in response to the selection requirement signal Srwa. As shown in FIG. 7, the assignment answer signal Sa has a sequence of an assignment response code word and the logical address “1”. The microcomputer  100  outputs the assignment answer signal Sa to the modulation circuit  110 . The modulation circuit  110  converts the assignment answer signal Sa into a corresponding radio answer signal RTa. The modulation circuit  110  feeds the radio answer signal RTa to the antenna  60 . The antenna  60  radiates and transmits the radio answer signal RTa. 
     The antenna  40  in the reader/writer RW receives the radio answer signal RTa from the IC card “A”. In the reader/writer RW, the received radio answer signal RTa is fed from the antenna  40  to the demodulation circuit  50 . The demodulation circuit  50  recovers the assignment answer signal Sa from the received radio answer signal RTa. The demodulation circuit  50  outputs the recovered assignment answer signal Sa to the microcomputer  10 . The microcomputer  10  sets an assignment-indicating flag for the logical address “1” in response to the recovered assignment answer signal Sa. Specifically, the microcomputer  10  generates data representing that the logical address “1” has been assigned to the IC card “A”. The microcomputer  10  writes the generated data into the memory  20 . 
     Subsequently, the microcomputer  10  in the reader/writer RW reads out the data from the memory  20  which represents the logical address “2” and the ID code word (the ID information) of the IC card “B”. The microcomputer  10  generates a selection requirement signal Srwb for the IC card “B” in response to the readout data. As shown in FIG. 7, the selection requirement signal Srwb has a sequence of the selection command, the logical address “2”, and the ID information of the IC card “B”. The microcomputer  10  outputs the selection requirement signal Srwb to the modulation circuit  30 . The modulation circuit  30  converts the selection requirement signal Srwb into a corresponding command radio signal referred to as a third command radio signal. The modulation circuit  30  outputs the third command radio signal to the antenna  40 . The third command radio signal is radiated by the antenna  40 , being transmitted from the reader/writer RW. 
     In the IC card “B”, the third command radio signal is received by the antenna  60 . The received third command radio signal is fed from the antenna  60  to the demodulation circuit  80 . The demodulation circuit  80  recovers the selection requirement signal Srwb from the received third command radio signal. The demodulation circuit  80  outputs the recovered selection requirement signal Srwb to the microcomputer  100 . The microcomputer  100  detects that the recovered selection requirement signal Srwb is directed to the IC card “B” on the basis of the ID information in the recovered selection requirement signal Srwb. In addition, the microcomputer  100  decides, from the recovered selection requirement signal Srwb, that the logical address “2” is assigned to the related IC card (the IC card “B”). The microcomputer  100  generates data representing that the logical address “2” is assigned to the related IC card (the IC card “B”). The microcomputer  100  writes the generated data into the memory  90 . Furthermore, the microcomputer  100  generates an assignment answer signal Sb in response to the selection requirement signal Srwb. As shown in FIG. 7, the assignment answer signal Sb has a sequence of the assignment response code word and the logical address “2”. The microcomputer  100  outputs the assignment answer signal Sb to the modulation circuit  110 . The modulation circuit  110  converts the assignment answer signal Sb into a corresponding radio answer signal RTb. The modulation circuit  110  feeds the radio answer signal RTb to the antenna  60 . The antenna  60  radiates and transmits the radio answer signal RTb. 
     The antenna  40  in the reader/writer RW receives the radio answer signal RTb from the IC card “B”. In the reader/writer RW, the received radio answer signal RTb is fed from the antenna  40  to the demodulation circuit  50 . The demodulation circuit  50  recovers the assignment answer signal Sb from the received radio answer signal RTb. The demodulation circuit  50  outputs the recovered assignment answer signal Sb to the microcomputer  10 . The microcomputer  10  sets an assignment-indicating flag for the logical address “2” in response to the recovered assignment answer signal Sb. Specifically, the microcomputer  10  generates data representing that the logical address “2” has been assigned to the IC card “B”. The microcomputer  10  writes the generated data into the memory  20 . 
     After both the logical addresses “1” and “2” have been assigned to the IC cards “A” and “B”, the microcomputer  10  in the reader/writer RW implements steps of controlling the IC cards “A” and “B” as follows. The microcomputer  10  generates a read requirement signal Rrwa for the IC card “A”. As shown in FIG. 7, the read requirement signal Rrwa has a sequence of a read command, the logical address “1”, and read requirement information. The microcomputer  10  outputs the read requirement signal Rrwa to the modulation circuit  30 . The modulation circuit  30  converts the read requirement signal Rrwa into a corresponding command radio signal referred to as a fourth command radio signal. The modulation circuit  30  outputs the fourth command radio signal to the antenna  40 . The fourth command radio signal is radiated by the antenna  40 , being transmitted from the reader/writer RW. 
     In the IC card “A”, the fourth command radio signal is received by the antenna  60 . The received fourth command radio signal is fed from the antenna  60  to the demodulation circuit  80 . The demodulation circuit  80  recovers the read requirement signal Rrwa from the received fourth command radio signal. The demodulation circuit  80  outputs the recovered read requirement signal Rrwa to the microcomputer  100 . The microcomputer  100  detects that the logical address represented by the recovered read requirement signal Rrwa agrees with the logical address “1” assigned to the related IC card (the IC card “A”). Thus, the microcomputer  100  recognizes that the recovered read requirement signal Rrwa is directed to the related IC card (the IC card “A”). Subsequently, the microcomputer  100  reads out data from the memory  90  in response to the read command and the read requirement information represented by the recovered read requirement signal Rrwa. Specifically, the readout data is designated by the read requirement information. The microcomputer  100  uses the readout data as read information. The microcomputer  100  generates a read answer signal Ra. As shown in FIG. 7, the read answer signal Ra has a sequence of a read response code word, the logical address “1”, and the read information. The microcomputer  100  outputs the read answer signal Ra to the modulation circuit  110 . The modulation circuit  110  converts the read answer signal Ra into a corresponding radio answer signal RUa. The modulation circuit  110  feeds the radio answer signal RUa to the antenna  60 . The antenna  60  radiates and transmits the radio answer signal RUa. 
     The antenna  40  in the reader/writer RW receives the radio answer signal RUa from the IC card “A”. In the reader/writer RW, the received radio answer signal RUa is fed from the antenna  40  to the demodulation circuit  50 . The demodulation circuit  50  recovers the read answer signal Ra from the received radio answer signal RUa. The demodulation circuit  50  outputs the recovered read answer signal Ra to the microcomputer  10 . The microcomputer  10  extracts the read information from the recovered read answer signal Ra. The microcomputer  10  writes the read information into the memory  20  as readout data. 
     Subsequently, the microcomputer  10  generates a read requirement signal Rrwb for the IC card “B”. As shown in FIG. 7, the read requirement signal Rrwb has a sequence of the read command, the logical address “2”, and read requirement information. The microcomputer  10  outputs the read requirement signal Rrwb to the modulation circuit  30 . The modulation circuit  30  converts the read requirement signal Rrwb into a corresponding command radio signal referred to as a fifth command radio signal. The modulation circuit  30  outputs the fifth command radio signal to the antenna  40 . The fifth command radio signal is radiated by the antenna  40 , being transmitted from the reader/writer RW. 
     In the IC card “B”, the fifth command radio signal is received by the antenna  60 . The received fifth command radio signal is fed from the antenna  60  to the demodulation circuit  80 . The demodulation circuit  80  recovers the read requirement signal Rrwb from the received fifth command radio signal. The demodulation circuit  80  outputs the recovered read requirement signal Rrwb to the microcomputer  100 . The microcomputer  100  detects that the logical address represented by the recovered read requirement signal Rrwb agrees with the logical address “2” assigned to the related IC card (the IC card “B”). Thus, the microcomputer  100  recognizes that the recovered read requirement signal Rrwb is directed to the related IC card (the IC card “B”). Subsequently, the microcomputer  100  reads out data from the memory  90  in response to the read command and the read requirement information represented by the recovered read requirement signal Rrwb. Specifically, the readout data is designated by the read requirement information. The microcomputer  100  uses the readout data as read information. The microcomputer  100  generates a read answer signal Rb. As shown in FIG. 7, the read answer signal Rb has a sequence of the read response code word, the logical address “2”, and the read information. The microcomputer  100  outputs the read answer signal Rb to the modulation circuit  110 . The modulation circuit  110  converts the read answer signal Rb into a corresponding radio answer signal RUb. The modulation circuit  110  feeds the radio answer signal RUb to the antenna  60 . The antenna  60  radiates and transmits the radio answer signal RUb. 
     The antenna  40  in the reader/writer RW receives the radio answer signal RUb from the IC card “B”. In the reader/writer RW, the received radio answer signal RUb is fed from the antenna  40  to the demodulation circuit  50 . The demodulation circuit  50  recovers the read answer signal Rb from the received radio answer signal RUb. The demodulation circuit  50  outputs the recovered read answer signal Rb to the microcomputer  10 . The microcomputer  10  extracts the read information from the recovered read answer signal Rb. The microcomputer  10  writes the read information into the memory  20  as readout data. 
     After the steps of controlling the IC cards “A” and “B” have been completed, the microcomputer  10  cancels the assignment of the logical address “1” to the IC card “A” as follows. The microcomputer  10  generates an address cancel requirement signal Lrw for the IC card “A”. As shown in FIG. 8, the address cancel requirement signal Lrw has a sequence of a cancel command and the logical address “1” which corresponds to an object to be canceled. The microcomputer  10  outputs the address cancel requirement signal Lrw to the modulation circuit  30 . The modulation circuit  30  converts the address cancel requirement signal Lrw into a corresponding command radio signal referred to as a sixth command radio signal. The modulation circuit  30  outputs the sixth command radio signal to the antenna  40 . The sixth command radio signal is radiated by the antenna  40 , being transmitted from the reader/writer RW. 
     In the IC card “A”, the sixth command radio signal is received by the antenna  60 . The received sixth command radio signal is fed from the antenna  60  to the demodulation circuit  80 . The demodulation circuit  80  recovers the address cancel requirement signal Lrw from the received sixth command radio signal. The demodulation circuit  80  outputs the recovered address cancel requirement signal Lrw to the microcomputer  100 . The microcomputer  100  detects that the logical address represented by the recovered address cancel requirement signal Lrw agrees with the logical address assigned to the related IC card (the IC card “A”). Accordingly, the microcomputer  100  decides that the recovered address cancel requirement signal Lrw is directed to the related IC card (the IC card “A”). The microcomputer  100  cancels the assignment of the logical address “1” to the related IC card (the IC card “A”) in response to the recovered address cancel signal Lrw. Specifically, the microcomputer  100  erases the data from the memory  90  which represents that the logical address “1” is assigned to the related IC card (the IC card “A”). In addition, the microcomputer  100  generates an address cancel answer signal La. As shown in FIG. 8, the address cancel answer signal La has a sequence of a cancel response code word and the logical address “1”. The microcomputer  100  outputs the address cancel answer signal La to the modulation circuit  110 . The modulation circuit  110  converts the address cancel answer signal La into a corresponding radio answer signal RVa. The modulation circuit  110  feeds the radio answer signal RVa to the antenna  60 . The antenna  60  radiates and transmits the radio answer signal RVa. 
     The antenna  40  in the reader/writer RW receives the radio answer signal RVa from the IC card “A”. In the reader/writer RW, the received radio answer signal RVa is fed from the antenna  40  to the demodulation circuit  50 . The demodulation circuit  50  recovers the address cancel answer signal La from the received radio answer signal RVa. The demodulation circuit  50  outputs the recovered address cancel answer signal La to the microcomputer  10 . The microcomputer  10  resets the assignment-indicating flag for the logical address “1” in response to the recovered address cancel answer signal La. Specifically, the microcomputer  10  erases the data from the memory  20  which represents that the logical address “1” has been assigned to the IC card “A”. In this way, the assignment of the logical address “1” to the IC card “A” is canceled. 
     Subsequently, the microcomputer  10  in the reader/writer RW assigns the logical address “1” to the IC card “C” as follows. The microcomputer  10  reads out the data from the memory  20  which represents the logical address “1” and the ID code word (the ID information) of the IC card “C”. The microcomputer  10  generates a selection requirement signal Srwc for the IC card “C” in response to the readout data. As shown in FIG. 8, the selection requirement signal Srwc has a sequence of the selection command, the logical address “1”, and the ID information of the IC card “C”. The microcomputer  10  outputs the selection requirement signal Srwc to the modulation circuit  30 . The modulation circuit  30  converts the selection requirement signal Srwc into a corresponding command radio signal referred to as a seventh command radio signal. The modulation circuit  30  outputs the seventh command radio signal to the antenna  40 . The seventh command radio signal is radiated by the antenna  40 , being transmitted from the reader/writer RW. 
     In the IC card “C”, the seventh command radio signal is received by the antenna  60 . The received seventh command radio signal is fed from the antenna  60  to the demodulation circuit  80 . The demodulation circuit  80  recovers the selection requirement signal Srwc from the received seventh command radio signal. The demodulation circuit  80  outputs the recovered selection requirement signal Srwc to the microcomputer  100 . The microcomputer  100  detects that the recovered selection requirement signal Srwc is directed to the IC card “C” on the basis of the ID information in the recovered selection requirement signal Srwc. In addition, the microcomputer  100  decides, from the recovered selection requirement signal Srwc, that the logical address “1” is assigned to the related IC card (the IC card “C”). The microcomputer  100  generates data representing that the logical address “1” is assigned to the related IC card (the IC card “C”). The microcomputer  100  writes the generated data into the memory  90 . Furthermore, the microcomputer  100  generates an assignment answer signal Sc in response to the selection requirement signal Srwc. As shown in FIG. 8, the assignment answer signal Sc has a sequence of the assignment response code word and the logical address “1”. The microcomputer  100  outputs the assignment answer signal Sc to the modulation circuit  110 . The modulation circuit  110  converts the assignment answer signal Sc into a corresponding radio answer signal RTc. The modulation circuit  110  feeds the radio answer signal RTc to the antenna  60 . The antenna  60  radiates and transmits the radio answer signal RTc. 
     The antenna  40  in the reader/writer RW receives the radio answer signal RTc from the IC card “C”. In the reader/writer RW, the received radio answer signal RTc is fed from the antenna  40  to the demodulation circuit  50 . The demodulation circuit  50  recovers the assignment answer signal Sc from the received radio answer signal RTc. The demodulation circuit  50  outputs the recovered assignment answer signal Sc to the microcomputer  10 . The microcomputer  10  sets the assignment-indicating flag for the logical address “1” in response to the recovered assignment answer signal Sc. Specifically, the microcomputer  10  generates data representing that the logical address “1” has been assigned to the IC card “C”. The microcomputer  10  writes the generated data into the memory  20 . 
     Subsequently, the microcomputer  10  in the reader/writer RW implements steps of controlling the IC card “C” as follows. The microcomputer  10  generates a read requirement signal Rrwc for the IC card “C”. As shown in FIG. 8, the read requirement signal Rrwc has a sequence of the read command, the logical address “1”, and read requirement information. The microcomputer  10  outputs the read requirement signal Rrwc to the modulation circuit  30 . The modulation circuit  30  converts the read requirement signal Rrwc into a corresponding command radio signal referred to as an eighth command radio signal. The modulation circuit  30  outputs the eighth command radio signal to the antenna  40 . The eighth command radio signal is radiated by the antenna  40 , being transmitted from the reader/writer RW. 
     In the IC card “C”, the eighth command radio signal is received by the antenna  60 . The received eighth command radio signal is fed from the antenna  60  to the demodulation circuit  80 . The demodulation circuit  80  recovers the read requirement signal Rrwc from the received eighth command radio signal. The demodulation circuit  80  outputs the recovered read requirement signal Rrwc to the microcomputer  100 . The microcomputer  100  detects that the logical address represented by the recovered read requirement signal Rrwc agrees with the logical address “1” assigned to the related IC card (the IC card “C”). Thus, the microcomputer  100  recognizes that the recovered read requirement signal Rrwc is directed to the related IC card (the IC card “C”). Subsequently, the microcomputer  100  reads out data from the memory  90  in response to the read command and the read requirement information represented by the recovered read requirement signal Rrwc. Specifically, the readout data is designated by the read requirement information. The microcomputer  100  uses the readout data as read information. The microcomputer  100  generates a read answer signal Rc. As shown in FIG. 8, the read answer signal Rc has a sequence of the read response code word, the logical address “1”, and the read information. The microcomputer  100  outputs the read answer signal Rc to the modulation circuit  110 . The modulation circuit  110  converts the read answer signal Rc into a corresponding radio answer signal RUc. The modulation circuit  110  feeds the radio answer signal RUc to the antenna  60 . The antenna  60  radiates and transmits the radio answer signal RUc. 
     The antenna  40  in the reader/writer RW receives the radio answer signal RUc from the IC card “C”. In the reader/writer RW, the received radio answer signal RUc is fed from the antenna  40  to the demodulation circuit  50 . The demodulation circuit  50  recovers the read answer signal Rc from the received radio answer signal RUc. The demodulation circuit  50  outputs the recovered read answer signal Rc to the microcomputer  10 . The microcomputer  10  extracts the read information from the recovered read answer signal Rc. The microcomputer  10  writes the read information into the memory  20  as readout data. 
     As previously indicated, the microcomputer  10  in the reader/writer RW operates in accordance with a program stored in its internal ROM. FIGS. 4 and 5 are a flowchart of the program in the microcomputer  10 . 
     As shown in FIG. 4, a first step  200  of the program outputs an ID information requirement signal Drw to the modulation circuit  30 . After the step  200 , the program advances to a step  210 . 
     The step  210  decides whether or not at least one ID information answer signal is present during a given time interval from the moment of the outputting of the ID information requirement signal Drw. When at least one ID information answer signal is present, the program advances from the step  210  to a step  211 . Otherwise, the program exits from the step  210 , and then the current execution cycle of the program ends (see FIG.  5 ). 
     The step  211  sets flags for ID code words represented by the ID information answer signals respectively. The step  211  writes signals (data) of the ID code words into the memory  20  as IC-card ID information. After the step  211 , the program advances to a step  212 . 
     The step  212  reads out the data from the memory  20  which represents the logical address “1” and the ID code word (the ID information) of the first IC card, for example, the IC card “A”. The step  212  generates a selection requirement signal Srwa for the first IC card (the IC card “A”) in response to the readout data. The step  212  outputs the selection requirement signal Srwa to the modulation circuit  30 . 
     A step  213  following the step  212  awaits an assignment answer signal Sa which is responsive to the selection requirement signal Srwa. The step  213  sets an assignment-indicating flag for the logical address “1” when detecting the assignment answer signal Sa. Specifically, in response to the assignment answer signal Sa, the step  213  generates data representing that the logical address “1” has been assigned to the first IC card (the IC card “A”). The step  213  writes the generated data into the memory  20 . Thus, the assignment of the logical address “1” to the first IC card (the IC card “A”) is completed. 
     A step  220  subsequent to the step  213  decides whether or not there is at least one IC card to which a logical address has not been assigned yet. When there is at least one IC card to which a logical address has not been assigned yet, the program advances from the step  220  to a step  230 . Otherwise, the program jumps from the step  220  to a step  240 . 
     The step  230  decides whether or not the assignment of a logical address to a remaining IC card is possible. When the assignment of a logical address to a remaining IC card is possible, the program returns from the step  230  to the step  212 . Otherwise, the program advances from the step  230  to the step  240 . 
     In the case where the assignment of the logical address “2” to the second IC card (for example, the IC card “B”) is possible, the program returns from the step  230  to the step  212 . In this case, the step  212  reads out the data from the memory  20  which represents the logical address “2” and the ID code word (the ID information) of the second IC card, for example, the IC card “B”. The step  212  generates a selection requirement signal Srwb for the second IC card (the IC card “B”) in response to the readout data. The step  212  outputs the selection requirement signal Srwb to the modulation circuit  30 . 
     The step  213  which follows the step  212  awaits an assignment answer signal Sb responding to the selection requirement signal Srwb. The step  213  sets an assignment-indicating flag for the logical address “2” when detecting the assignment answer signal Sb. Specifically, in response to the assignment answer signal Sb, the step  213  generates data representing that the logical address “2” has been assigned to the second IC card (the IC card “B”). The step  213  writes the generated data into the memory  20 . Thus, the assignment of the logical address “2” to the second IC card (the IC card “B”) is completed. 
     The step  220  subsequent to the step  213  decides whether or not there is at least one IC card to which a logical address has not been assigned yet. When there is at least one IC card to which a logical address has not been assigned yet, the program advances from the step  220  to the step  230 . Otherwise, the program jumps from the step  220  to the step  240 . 
     The step  230  decides whether or not the assignment of a logical address to a remaining IC card is possible. When the assignment of a logical address to a remaining IC card is possible, the program returns from the step  230  to the step  212 . Otherwise, the program advances from the step  230  to the step  240 . 
     In the case where the logical addresses “1” and “2” have been assigned to the first and second IC cards (the IC cards “A” and “B”) respectively, the program advances from the step  230  to the step  240 . 
     The step  240  decides whether or not the execution of a command to control the first IC card (the IC card “A”) is required. When the execution of the command to control the first IC card (the IC card “A”) is required, the program advances from the step  240  to a step  241 . In addition, the step  240  decides whether or not the execution of a command to control the second IC card (the IC card “B”) is required. When the execution of the command to control the second IC card (the IC card “B”) is required, the program advances from the step  240  to the step  241 . When neither the execution of the command to control the first IC card (the IC card “A”) nor the execution of the command to control the second IC card (the IC card “B”) is required, the program advances from the step  240  to a step  260  in FIG.  5 . 
     The step  241  executes the command to control the first IC card (the IC card “A”) or the command to control the second IC card (the IC card “B”). In the case of the execution of the command to control the first IC card (the IC card “A”), the step  241  generates a read requirement signal Rrwa for the first IC card. The step  241  outputs the read requirement signal Rrwa to the modulation circuit  30 . In the case of the execution of the command to control the second IC card (the IC card “B”), the step  241  generates a read requirement signal Rrwb for the second IC card. The step  241  outputs the read requirement signal Rrwb to the modulation circuit  30 . In addition, the step  241  awaits a read answer signal Ra or Rb which is responsive to the read requirement signal Rrwa or Rrwb. Upon the detection of the read answer signal Ra or Rb, the step  241  extracts the read information from the read answer signal Ra or Rb. The step  241  writes the read information into the memory  20  as readout data. 
     A step  250  following the step  241  decides whether or not the execution of all the commands to control the respective address-assigned IC cards has been completed. When the execution of all the commands has been completed, the program advances from the step  250  to the step  260  in FIG.  5 . Otherwise, the program returns from the step  250  to the step  240 . 
     The step  260  decides whether or not a command to control the remaining IC card (the third IC card, for example, the IC card “C”), to which any logical address has not been assigned yet, is required to be executed. When the command to control the third IC card is required to be executed, the program advances from the step  260  to a step  261 . Otherwise, the program exits from the step  260 , and then the current execution cycle of the program ends. 
     The step  261  generates an address cancel requirement signal Lrw for the fist IC card (the IC card “A”) to which the logical address “1” has been assigned. The step  261  outputs the address cancel requirement signal Lrw to the modulation circuit  30 . In addition, the step  261  awaits an address cancel answer signal La which is responsive to the address cancel requirement signal Lrw. The step  261  resets the assignment-indicating flag for the logical address “1” when detecting the address cancel answer signal La. Specifically, the step  261  erases the data from the memory  20  which represents that the logical address “1” has been assigned to the first IC card (the IC card “A”). 
     A step  262  subsequent to the step  261  reads out the data from the memory  20  which represents the logical address “1” and the ID code word (the ID information) of the third IC card, for example, the IC card “C”. The step  262  generates a selection requirement signal Srwc for the third IC card (the IC card “C”) in response to the readout data. The step  262  outputs the selection requirement signal Srwc to the modulation circuit  30 . 
     A step  263  following the step  262  awaits an assignment answer signal Sc which is responsive to the selection requirement signal Srwc. The step  263  sets the assignment-indicating flag for the logical address “1” when detecting the assignment answer signal Sc. Specifically, in response to the assignment answer signal Sc, the step  263  generates data representing that the logical address “1” has been assigned to the third IC card (the IC card “C”). The step  263  writes the generated data into the memory  20 . Thus, the assignment of the logical address “1” to the third IC card (the IC card “C”) is completed. 
     A step  264  subsequent to the step  263  executes a command to control the third IC card (the IC card “C”). Specifically, the step  264  generates a read requirement signal Rrwc for the third IC card. The step  264  outputs the read requirement signal Rrwc to the modulation circuit  30 . In addition, the step  264  awaits a read answer signal Rc which is responsive to the read requirement signal Rrwc. When the read answer signal Rc is received, the step  264  extracts the read information from the read answer signal Rc. The step  264  writes the read information into the memory  20  as readout data. After the step  264 , the current execution cycle of the program ends. 
     As previously indicated, the microcomputer  100  in the IC card “A” operates in accordance with a program stored in its internal ROM. FIG. 6 is a flowchart of the program in the microcomputer  100 . 
     As shown in FIG. 6, a first step  300  of the program decides whether or not an ID information requirement signal Drw is present. When the ID information requirement signal Drw is present, the program advances from the step  300  to a step  310 . Otherwise, the step  300  is repeated. 
     The step  310  reads out the ID data from the memory  90 . The step  310  generates an ID information answer signal Da from the readout data. The step  310  outputs the ID information answer signal Da to the modulation circuit  110 . After the step  310 , the program advances to a step  320 . 
     The step  320  decides whether or not a selection requirement signal Srwa directed to the IC card “A” is present by referring to the ID code word (the ID information) in the selection requirement signal Srwa. When the selection requirement signal Srwa is present, the program advances from the step  320  to a step  330 . Otherwise, the step  320  is repeated. 
     The step  330  decides, from the recovered selection requirement signal Srwa, that the logical address “1” is assigned to the IC card “A”. The step  330  generates data representing that the logical address “1” is assigned to the IC card “A”. The step  330  writes the generated data into the memory  90 . Furthermore, the step  330  generates an assignment answer signal Sa in response to the selection requirement signal Srwa. The step  330  outputs the assignment answer signal Sa to the modulation circuit  110 . After the step  330 , the program advances to a step  340 . 
     The step  340  decides whether or not a command to control an IC card (for example, the IC card “A”) is present. An example of the command is a read requirement signal (a read requirement signal Rrwa). When the command is present, the program advances from the step  340  to a step  350 . Otherwise, the step  340  is repeated. 
     The step  350  decides whether or not the logical address represented by the command (for example, the read requirement signal) agrees with the logical address “1” assigned to the IC card “A”. In other words, the step  350  decides whether or not the command is directed to the IC card “A”. When the logical address represented by the command agrees with the logical address “1”, that is, when the command is directed to the IC card “A”, the program advances from the step  350  to a step  360 . Otherwise, the program returns from the step  350  to the step  340 . 
     The step  360  decides whether the command is equal to or different from an address cancel requirement signal Lrw. When the command is different from the address cancel requirement signal Lrw, the program advances from the step  360  to a step  370 . When the command is equal to the address cancel requirement signal Lrw, the program advances from the step  360  to a step  380 . 
     The step  370  executes the command. In the case where the command is equal to the read requirement signal Rrwa, the step  370  reads out data from the memory  90  in response to the read command and the read requirement information represented by the read requirement signal Rrwa. Specifically, the readout data is designated by the read requirement information. The step  370  uses the readout data as read information. The step  370  generates a read answer signal Ra. The step  370  outputs the read answer signal Ra to the modulation circuit  110 . After the step  370 , the program returns to the step  340 . 
     The step  380  cancels the assignment of the logical address “1” to the IC card “A” in response to the address cancel signal Lrw. Specifically, the step  380  erases the data from the memory  90  which represents that the logical address “1” is assigned to the IC card “A”. In addition, the step  380  generates an address cancel answer signal La. The step  380  outputs the address cancel answer signal La to the modulation circuit  110 . After the step  380 , the program returns to the step  320 . 
     The telephone set on which the reader/writer RW is provided may be replaced by a dispenser or an automatic vending machine. 
     The microcomputers  10  and  100  may be replaced by exclusive control circuits composed of discrete analog circuits or discrete digital circuits. 
     At least part of the combination of the microcomputer  10 , the memory  20 , the modulation circuit  30 , and the demodulation circuit  50  may be formed by a single IC chip. 
     At least part of the combination of the memory  90 , the microcomputer  100 , the power supply circuit  70 , the modulation circuit  110 , and the demodulation circuit  80  may be formed by a single IC chip.