 |
Description  |
|
|
TECHNICAL FIELD
The present invention relates to a non-contact type integrated circuit (IC)
card not having contact terminals for a power source and for inputting and
outputting signals.
BACKGROUND ART
There has been known an IC card which as not contact terminals for
receiving signals from an external device or for outputting signals
thereto via a magnetic or capacitive coupling therewith. When using the
non-contact type IC card, as compared with the card achieving
communications of signals via contact terminals, the read operation is
facilitated since, for example, when a person having the card in his or
her hand approaches the external device, data stored in the card can be
read therefrom into the external device. Moreover, there can be prevented
such problems associated with the card achieving input and output
operations of data via contact terminals as a contact failure due to dirt,
erosion, etc. of terminal contact points and wrong operations due to a
leakage current.
For the read operation of the non-contact type IC card, the card bearer
having the card with him or her need only approach the reader and there is
unnecessitated a read operation to insert the card into the reader.
Consequently, the card is suitable for a check of sequential passage of
many persons, for example, the card is suitably used as a commuter pass or
a key for checking entrance an exit for a particular room.
In a case where the non-contact type IC card is adopted as a commuter pass
or a key for checking entrance and exit for a room, ID data is read from a
memory of the IC card for a collation thereof such that when the collation
results in a coincidence, the passage of the gate or the entrance for the
room is admitted. At the same time, historical data of uses of the IC card
is written in the memory thereof.
When a non-contact type IC card is brought into an area accessible to the
reader-writer, the collation and the write operation of the history are
accomplished. Since the accessible area has a range of a certain
magnitude, when the card is employed as, for example, a commuter pass,
there may occur depending on actions of the card holder a case where an
identical card enters two or more times the area accessible to the
reader-writer installed at the gate. Namely, it may possible occur, the
user puts the card into the area, removes the card from the area, and then
puts again the card into the area. In such a case, it is necessary to
avoid the write operation of history in the second access.
Conventionally, in the case above, the second access of an identical card
is detected by the reader-writer to inhibit the write operation of new
data on the card. However, since passage of many cards is required to be
checked in a short period of time at the gate, it is necessary for the
reader-writer, after an access of a card, to wait for passage of a
subsequent card. Consequently, there does not exit any marginal time
enough to check the second access.
In consequence, it is desired that the operation of a card is inhibited for
a fixed period of time after a passage thereof. However, in a card not
having a power source therein, namely, a card of an external power supply
type, an electromagnetic energy supplied from an external device is
rectified to obtain a direct-current (dc) voltage necessary for an
internal circuit thereof. Consequently, after the external energy supply
is interrupted, it is difficult to control the operation inhibition for a
fixed period of time. For example, after the external energy supply is
stopped, the circuit in the card may be operated by energy resultant from
discharge of electric charges accumulated in a smoothing capacitor of the
power source circuit. However, since the operation of the circuit is
determined by a value of a current consumed by the circuit and the energy
accumulated in the smoothing capacitor, it is difficult to set the period
for inhibiting the operation.
Moreover, in such a non-contact type IC card, since the contact
(approaching) state between the card and the reader-writer cannot be
fixedly established, communications of data and power source become to be
unstable in some cases. For example, in a card of the external power
supply type which receives supply of power via energy such as an
electromagnetic field from an external power source, the card is supplied
with power only when the card is in the proximity of the reader-writer.
When the card is apart from the reader-writer, the power is not supplied
thereto. In consequence, in a case where the bearer of the card puts the
card close to the reader-writer to write data received from the
reader-writer in the memory of the card, when the contact state is changed
because the distance between the card and the reader-writer is increased
due to movement or the like of the bearer, the power supply from the
reader-writer to the card is interrupted. Consequently, the write
operation of data in the memory of the card is stopped at an intermediate
point and hence data is stored in the memory in an incomplete state.
Since such incomplete data is directly stored in the memory, when the data
is read therefrom by the reader-writer, it is impossible to accomplish a
predetermined check operation. For example, when the card is adopted as a
commuter pass, the states of the pass such as a period thereof, a valid
period thereof, a station name where the bearer took the train, and time
when the bearer took the train are required to be accurate in any case.
Otherwise, there arises a problem that the essential object of the card
cannot be achieved.
It is therefore an object of the present invention to provide a non-contact
type IC card guaranteeing the normal operation even when an abnormality
occurs in an access operation between the card and the external device,
thereby solving the problems of the non-contact type IC card.
Namely, the present invention aims at providing a non-contact type IC card
capable of preventing inappropriate data from being written therein even
when the card enters an area accessible to the external device for a
plurality of times at a short interval of time.
Moreover, another object of the present invention is to provide a
non-contact type IC card guaranteeing the normal operation even when an
abnormality occurs in the contact state during a write operation of data
from the external device.
DISCLOSURE OF THE INVENTION
In accordance with the present invention, a non-contact type IC card
achieving communications of signals with an external device in a
noncontact manner includes main circuit means for conducting various
operations based on functions of the IC card, operation inhibition signal
generating means for creating an operation inhibition signal to inhibit
the operation of the main circuit means for a predetermined period of
time, and control means for controlling the main circuit means and the
operation inhibition signal generating means. The control means operates
the operation inhibition signal generating means when the operation of the
main circuit means is finished and inhibits the operation of the main
circuit means for a predetermined period of time according to the
operation inhibition signal from the operation inhibition signal
generating means.
In accordance with the present invention, when an operation of the main
circuit means is finished, the operation inhibition signal generating
means operates to create an operation inhibition signal, thereby
inhibiting the operation of the main circuit means for a predetermined
period of time. In consequence, in a case where the card enters an area
accessible to the external device a plurality of times during a short
period of time, the second and subsequent accesses can be inhibited and
hence the improper operation due to the plural accesses can be avoided.
Moreover, since the inhibition of such accesses need not be monitored by
the external device, the load imposed on the external device can be
minimized.
In accordance with the present invention, a non-contact type IC card
includes communicating means for communicating signals with an external
device in a non-contact manner, a memory for storing therein data sent
from the external device, and control means for controlling operations of
the communicating means and the memory. The memory has an area subdivided
into a plurality of areas for storing therein data sent from the external
device, and the control means reads, when the data is to be read from the
memory, the data from one of the plural areas in which the data is
normally stored.
In accordance with the non-contact type IC card of the present invention,
an area of a memory for storing therein data sent from the external device
is subdivided into a plurality of areas such that when reading data from
the memory, the data is read from an area of the plural areas in which the
data is normally stored. In consequence, even when the data recorded in
one of the areas is wrong, the data can be read from the other area.
Consequently, even when an abnormality occurs in a write operation of
data, the data can be read therefrom.
In consequence, a write operation of wrong data or absence of record data
which occurs when the card holder moves therewith at a high speed can be
coped with by executing a predetermined processing with the normal data
read from the memory.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a functional block diagram showing an embodiment of a non-contact
type IC card in accordance with the present invention;
FIG. 2 a circuit diagram showing a specific example of the card of FIG. 1;
FIG. 3 is a timing chart showing the operation of the circuit of FIG. 2;
FIG. 4 is a timing chart showing the operation of the control circuit of
FIG. 2;
FIG. 5 is a block diagram showing another embodiment of a non-contact type
IC card in accordance with the present invention;
FIG. 6 shows a write operation of data in a memory of the card of FIG. 5;
FIG. 7 shows a write operation of data in a memory of the card of FIG. 5;
FIG. 8 shows a write operation of data in a memory of the card of FIG. 5;
FIG. 9 shows a write operation of data in a memory of the card of FIG. 5;
FIG. 10 is a flowchart showing the operation of the card of FIG. 5;
FIG. 11 is a flowchart showing the operation of the card of FIG. 5;
FIG. 12 is a flowchart showing the operation of the card of FIG. 5; and
FIG. 13 is a flowchart showing the operation of the card of FIG. 5.
BEST MODE FOR CARRYING OUT THE INVENTION
Referring next to the accompanying drawings, description will be given in
detail of a non-contact type IC card in accordance with the present
invention.
FIG. 1 shows an embodiment of a non-contact type IC card in accordance with
the present invention. This IC card is an IC card of an external power
supply type receiving power supply from an external device. In this
connection, portions not directly related to the present invention are not
shown in this embodiment.
The card has a power source circuit 10. The power source circuit 10 is a
power supply circuit for transmitting power supplied from a reader-writer
to the respective components of the card. The power source circuit 10 is
coupled with the reader-writer via a magnetic coupling shown in the
diagram or a capacitive coupling not shown therein to receive power
supplied from the reader-writer.
The power source circuit 10 is connected to a main circuit 16. The main
circuit 16 is a circuit accomplishing operations according to various
functions of the card and is constituted with a central processing unit
(CPU), a memory, etc. For example, as shown in FIG. 5, there are included
a memory 32 and a memory control section 36.
The main circuit 16 has a function to read, when the card is put by the
bearer into an area accessible to the reader-writer, ID data from the
memory 16 to output the data to the reader-writer and/or a function to
collate ID data sent from the reader-writer with data stored in the memory
32. Moreover, the main circuit 16 writes in the memory 32, after the
passage of the bearer is admitted by the reader-writer as a result of such
a collation of the ID data, an indication that the passage is admitted by
the data sent from the reader-writer.
The card in addition has a re-access inhibition time setting circuit 12.
The circuit 12 is connected to the power source circuit 10 to set a period
of time for inhibiting a re-access based on a voltage supplied from the
power source circuit 10 and a control signal sent from the control circuit
14 and then outputs a re-access inhibition time setting signal to the
control circuit 14.
The control circuit 14 is connected to the circuit 12 and the main circuit
16 to inhibit the operation of the main circuit 16 for a predetermined
period of time according to the re-access inhibition time setting signal
outputted from the circuit 12. Furthermore, the control circuit 14
controls, in accordance with an access operation terminating signal
transmitted from the main circuit 16, the setting operation of the circuit
12.
FIG. 2 shows a more specific construction of the circuit of FIG. 1. Four
diodes D1, D2, D3, and D4; two capacitors C1 and C2; and a regulator 20
are disposed as elements corresponding to the power source circuit 10 of
FIG. 10. Electric energy supplied from the reader-writer via a coil L is
rectified by the diodes D1 to D4 and the regulator 20. Alternating-current
components are removed therefrom by the capacitors C1 and C2 such that the
resultant signal is sent to the main circuit 1 and the re-access
inhibition time setting circuit 12.
The circuit 12 possesses a transistor Q. The transistor Q has an emitter
region connected to an output of the power source circuit 10 and a base
region which is connected via a resistor R2 to the output from the power
source 10 and which is connected via a resistor R4 to an output of the
control circuit 14. The transistor Q has a collector region linked with an
anode of the diode D5 having a cathode connected to a resistor R1 and a
capacitor C3. Other terminals respectively of the resistor R1 and the
capacitor C3 are grounded. The cathode of the diode D5 is further
connected to a gate region of an field-effect transistor (FET) of an
n-type channel 24. The FET 24 has a drain region which is linked via a
resistor R3 to an output of the power source circuit 10 and which is
linked to a Schmitt trigger circuit 22, whereas the FET 24 has a source
region grounded. The Schmitt trigger circuit 22 has an output connected to
an input of the control circuit 14.
Referring to the timing chart of FIG. 3, the operation of the circuit 12
will be described. In a case where the card is used as a commuter pass and
is put into an accessible area of the reader-writer at a gate twice in a
short period of time, the circuit 12 sets an inhibition time for
inhibiting the second access.
At a point A of FIG. 2, power as indicated by A in FIG. 3 is supplied as an
output from the power source circuit 10. Namely, when the card enters the
accessible area of the reader-writer twice (at points of time t1 and t4),
energy is supplied at each point of time from the reader-writer via the
power supply circuit 10. When power is supplied at the point A, the power
is fed to the main circuit 16, thereby enabling the main circuit 16 to
operate. During the operation of the main circuit 16, as indicated by B in
FIG. 3, the main circuit 16 is powered and a signal B denoting that the
main circuit 16 is operable is delivered via the resistor R4 to the base
region of the transistor Q (time t1). Consequently, the transistor Q is in
a non-conductive state and the power supplied to the point A is not fed to
a point C. The potential of the point C is hence at a ground level as
designated by C in FIG. 3. In consequence, since any signal is not
inputted to the gate region of the FET 24, the FET 24 is in a
non-conductive state and a point D of the drain region of the FET 24 is
supplied with the output from the power source circuit 10 as indicated by
D in FIG. 3. As a result, the output from the Schmitt trigger circuit 22
is also as denoted by E in FIG. 3 and the output E is transmitted to the
control circuit 14. The control circuit 14 outputs, according to the
output E, a signal allowing the operation of the main circuit 16 to the
main circuit 16.
When the operation of the main circuit 16 is finished (time t2), the output
of the signal B from the control circuit 14 is stopped. This sets the base
region of the transistor Q to a low level and hence the transistor Q
becomes to be conductive, which increases the potential at the point C as
denoted by C in FIG. 3. At the time t3 when the power supply A from the
power source circuit 10 is interrupted, the power from the power source
circuit 10 is not supplied to the point C. However, according to a
discharging operation of electric charge accumulated in the capacitor C3
during the power supply period, the potential of the point C is gradually
decreased in accordance with the time constant of the capacitor and the
resistor as indicated by C in FIG. 3.
At a point of time T4, when the card is again put into the accessible area
of the reader-writer and the second power is supplied from the power
source circuit 10, a signal B indicating that power can be supplied to the
main circuit 16 is sent from the control circuit 14 to the transistor Q,
which sets the transistor Q to a non-conductive state. In consequence, the
point C is kept remained in a state where power is not supplied from the
power source circuit 10 and hence the potential of the point C continues
lowering as shown in FIG. 3. As a result, since the potential inputted to
the gate region of the FET 24 continues decreasing and the current flowing
from the drain region to the source region of the FET 24 is minimized, the
potential of the point D is gradually increased. In consequence, the
voltage D inputted to the Schmitt trigger circuit 22 is gradually
increased, at a point of time t5 where the voltage D exceeds the
predetermined value, a signal E is outputted from the Schmitt trigger
circuit 22. According to this output E, the control circuit 14 outputs a
signal allowing the operation of the main circuit 16 to the main circuit
16.
As above, after the output E from the Schmitt trigger circuit 22 is set to
a high level, the operation of the main circuit 16 is allowed.
Consequently, after the first operation (access to the reader-writer) of
the main circuit 16 at the point of time t2 is finished, the operation of
the main circuit 16 is not allowed until a point of time t5. In
consequence, even in a case where the card is put to the accessible area
at the time t4 to supply power from the power source circuit 10, the main
circuit 16 does not achieve any operation. As above, after the first
access is terminated, the access to the reader-writer can be inhibited for
a fixed period of time.
Subsequently, the operation of the control circuit 14 will be described by
reference to the flowchart of FIG. 4. Whether or not power is being
supplied is judged (step 102). If this is not the case, a wait operation
is effected until the power-on state occurs. If the power is being
supplied, it is assumed that the card has entered the accessible area of
the reader-writer and a check is made to determine whether or not the
point of time is during the re-access inhibition period (step 104). If
this is the case, whether or not the power is off is judged (step 106). If
the power is not off, a wait operation is achieved until the power is
turned off. When the power is turned off, it is assumed that the card is
removed from the accessible area of the reader-writer and control is
returned to the first step 102.
In the step 104, if the current point is not in the re-access inhibition
period, it is assumed that the access to the reader-writer becomes to be
possible and then a predetermined data communication is achieved with the
reader-writer (step 108). Whether or not the data communication has been
completed is judged (step 110). If this is the case, the re-access
inhibition period is set (step 112). Thereafter, whether or not the power
is turned off is checked (step 114). If the power is not turned off, a
wait operation is executed until the power is turned off. When the power
is turned off, it is assumed that the card is removed from the accessible
area of the reader-writer and then control is returned to the first step
102.
Also in the case where the data communication is not completed in the step
110, whether or not the power is turned off is judged (step 116) such that
if this is the case, control is passed to the step 102.
As above, in accordance with the card of the present embodiment, after an
access is finished, the re-access can be inhibited for a fixed period of
time. In consequence, in a case where the card enters the accessible area
of the reader-writer two or more times in a short period of time, the
second and subsequent accesses to the reader-writer can be inhibited and
hence the inappropriate operation due to a plurality of accesses can be
prevented. Moreover, since the card has the function to inhibit the
access, the operation to inhibit the re-access of the card need not be
achieved by the reader-writer, thereby minimizing the load imposed on the
reader-writer.
In accordance with the card, in a case where, for example, it is necessary
at a gate to check passages of many cards in a short period of time, the
reader-writer is not required to check the re-access. Consequently, after
an access of a card, the reader-writer can immediately await a passage of
the next card, which enables the accesses to many cards in a smooth
manner.
In accordance with the present invention as described above, when the
operation of the main circuit means is terminated, the operation
inhibition signal generating means operates to create an operation
inhibition signal, thereby inhibiting the operation of the main circuit
means for a predetermined period of time. Consequently, in a case where
the card enters an area accessible to the external device a plurality of
times in a short period of time, the second and subsequent accesses can be
inhibited, thereby preventing the inappropriate operation due to the
plural accesses. Furthermore, since the access inhibition above need not
be monitored by the external device, the load on the external device can
be reduced.
FIG. 5 shows another embodiment of a non-contact type IC card in accordance
with the present invention. This card 30 includes a memory 32 of an
electrically erasable programmable ROM (EEPROM) or the like. The memory 32
has two areas 321 and 322 in this embodiment. As will be described later,
in the IC card of the embodiment, data items are recorded in these two
areas 321 and 322 together with numbers indicating sequence numbers of the
data item write operation. In a data read operation, the data items are
read by referencing the numbers in the areas so that data is read from one
of the areas last undergone a recording operation. Moreover, in a case
where data recorded in either one of the two areas 321 and 322 is in a
destroyed state due to, for example, an interruption of a data write
operation, data recorded in the remaining one thereof is read. With the
provision of two areas, even when an abnormality occurs during a data
write operation in one of the areas of the card, data can be read from the
remaining area for use thereof, which thereby prevents an operation
failure. In this connection, the number of areas disposed in the memory 32
is not limited to two, namely, the number may be three or more.
The card 30 further include a read area deciding section 34 connected to
the memory 32. The read area deciding section 34 judges to determine from
which one of the two areas 321 and 322 of the memory data is to be read.
The memory 32 and the section 34 are connected to a memory control section
36. The section 36 controls according to commands an operation to write in
the memory 32 data sent from a reader-writer, not shown, via a noncontact
terminal 40 and a modulating and demodulating section 38 and an operation
to read data stored in the memory 32 so as to feed the data to the
reader-writer. The memory control section 36 achieves a control operation
to record data sent from the reader-writer alternately in the two areas
321 and 322 together with the numbers indicating the recording order.
Moreover, particularly, the section 36 controls a data read operation to
read data from an area determined by the section 34.
The modulating and demodulating section 38 modulates data outputted from
the memory control section 36 to the reader-writer and demodulates data
inputted from the reader-writer via the noncontact terminal 40. The
terminal 40 is used to communicate data with the reader-writer, not shown,
in a noncontact manner.
The power source circuit 10 is, like in the embodiment described above, a
circuit to send power supplied from the reader-writer to the respective
sections of the card 30. The power source circuit 10 is coupled with the
reader-writer via a magnetic coupling shown in the diagram or a capacitive
coupling, not shown, to receive power supplied from the reader-writer.
Referring to the changes in the recording state of the memory 32 shown in
FIGS. 6 to 9, description will be given of the operation to write data in
the memory 32. In each of the areas 321 and 322, there are disposed the
areas including a data area D in which data is recorded, a number area N
in which a number of a write sequence of data is recorded, and a check
code area in which a check code is recorded.
Immediately after the card 30 is issued, as shown in FIG. 6, there are
recorded data 1, "0" as the number denoting the write sequence, and a
predetermine code C such as a DDC code in the data areas D, N, and C,
respectively. The data recorded in the data area D is one of various kinds
of data items such as an ID number communicated between the IC card and
the reader-writer. The number indicating the write sequence recorded in
the number area N indicates a write sequential number of data recorded in
the data area D of each of two areas. As shown in FIG. 6, immediately
after the issuance of the card 30, "0" is recorded as an initial value.
The check code recorded in the check code area C is used to determine
whether or not the data is normal, and one of the known various codes is
employed.
For the data to be recorded in the data area D, data inputted from the
reader-writer via the noncontact terminal 40 is demodulated by the
modulating and demodulating section 38 and is then sent from the memory
control section 36 to the memory 32 so as to be stored therein. Moreover,
the data to be recorded in the data area D and the code to be recorded in
the check code area C are generated by the memory control section 36 and
is then sent to the memory 32 to be stored therein.
Immediately after the issuance of the card 30, any data is not recorded in
the area 322. Consequently, in a data read operation, the data in the area
322 is assumed to be in a destroyed state by the read area deciding
section 34 such that data recorded in the area 321 is read by the memory
control section 36.
Next, as shown in FIG. 7, a first data write operation is accomplished in
the area 322. As shown in this diagram, data 2 is recorded in the data
area D and a number "1" is recorded as a data record sequential number in
the number area N. In the check code area C, there is recorded a
predetermined check code. In a state in which the first data write
operation has been conducted, the section 34 compares the number recorded
in the number area N of the area 321 with that recorded in the number area
N of the area 322 to determine that the data recorded in the area 322 is
the latest data. Consequently, in the data read operation, the data 2
recorded in the area 322 is read.
In addition, as shown in FIG. 8, a second data write operation is achieved
in the area 321. The data write operations are conducted as above in the
two areas 321 and 322 in an alternating manner.
As a result of the second data write operation of FIG. 8, in the area 321,
data 3 is recorded in the data area D, a number "2" is recorded as a data
record sequential number in the number area N, and a predetermined check
code is recorded in the check code area C. In a state where the second
data write operation is achieved as above, the data recorded in the area
321 is the latest data and hence the data 3 recorded in the area 321 is
read in the data read operation.
Subsequently, in a similar manner, data write operations are conducted in
the two areas 321 and 322 in an alternating fashion. For example, as shown
in FIG. 9, in a case where after the n-th data is correctly written in the
area 322, if the (n+1)-th data write operation in the area 321 results in
a failure, the data in the area 321 is in the destroyed state.
Consequently, in this case, the read area deciding section 34 assumes,
without achieving the comparison between the numbers stored in the number
areas N of the two areas, that the data recorded in the area 322 is the
latest data such that the data is read by the memory control unit 36.
Subsequently, the operation of the IC card 30 will be described according
to the flowcharts shown in FIGS. 10 to 13.
First, in a step 202 of FIG. 10, normality or abnormality of the data in
the two areas 321 and 322 of the memory 32 is judged by checking the check
code by the read area deciding section 34. Whether or not the data of each
of the areas 321 and 322 is wrong (NG) is judged (step 204). If this is
the case, the section 34 outputs a signal of the condition to the section
36, which then proceeds to the processing of FIG. 11.
In a step 230 of FIG. 11, the section 36 judges to determine whether or not
a read operation is to be executed. If this is the case, a signal
indicating that the memory 32 is in the destroyed state is outputted from
the section 36 to the reader-writer (step 232). Otherwise, whether or not
a write operation is to be executed is judged (step 234). If this is the
case, data is written in the data area D of the area 321 and a number "0"
is recorded in the number area N (Step 236). If the write operation is not
assumed in the step 234, control is returned to the step 230 to repeatedly
achieve the same operation.
In the step 204 of FIG. 10, if data of both of the two areas 321 and 322
are not wrong (NG), control is passed to a step 206 such that the section
34 checks to determine whether or not the data in the area 321 is NG. If
this is the case, control is transferred to the processing of FIG. 12.
In a step 240 of FIG. 12, the section 36 judges to decide whether or not a
read operation is to be executed. If this is the case, data recorded in
the area 322 is read to be transmitted to the reader-writer (step 242).
Otherwise, whether or not a write operation is to be achieved is judged
(step 244). If this is the case, data is written is the data area D of the
area 321 and the number to be written in the number area N is updated
(step 246). In the step 244, if the write operation is not assumed,
control is returned to the step 240 to repeatedly accomplish the same
operation.
In the step 206 of FIG. 10, when the data in the area 321 is not NG,
control proceeds to a step 208 in which the section 34 judges to determine
whether or not the data in the area 322 is NG. If this is the case,
control is passed to the processing of FIG. 13. In a step 250 of FIG. 13,
the section 36 judges to decide whether or not a read operation is to be
executed. If this is the case, data recorded in the area 321 is read to be
transmitted to the reader-writer (step 252). In the case of a write
operation, data is written in the data area D of the area 322 and a number
to be written in the number area N is updated (step 256). In the step 254,
when the write operation is not assumed, control is returned to the step
250 to repeatedly accomplish the same operation.
In the step 208 of FIG. 10, when the data in the area 322 is not NG,
control proceeds to a step 210 such that the section 34 judges to
determine whether or not the number recorded in the number area N of each
of the areas is successive. If this is not the case, data of each of the
areas is assumed to have been destroyed and control is transferred to the
processing of FIG. 11. If the number is consecutive, the number of the
area 321 is compared with that of the area 322 (step 212). If the number
of the area 321 is larger than that of the area 322, the section 34
assumes that the data recorded in the area 321 is the latest data and then
passes control to the processing of FIG. 13 to read data from the area
321. In the step 212, if the number of the area 321 is smaller than that
of the area 322, the section 34 assumes that the data recorded in the area
322 is the latest data and then transfers cont | | |
