Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
2002-06-14
2004-08-24
Frech, Karl D. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
C235S436000, C235S437000, C235S438000
Reexamination Certificate
active
06779724
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an IC card reader/writer and method for receiving data transmitted from an IC card.
BACKGROUND ART
FIG. 11
shows a conventional general configuration of a reader/writer for an IC card with an external terminal (hereafter simply referred to as an IC card). IEC/ISO7816 is available as a standard regarding IC cards. In
FIG. 11
, numeral
1000
designates an IC card reader/writer, numeral
101
designates a CPU, and numeral
109
designates an IC card. Furthermore, in the IC card reader/writer
1000
, numeral
201
designates a transmission buffer that temporarily stores transmitted data transmitted from the CPU
101
. Numeral
202
designates a parity generation section that calculates the parity of the transmitted data and adds the parity. Numeral
203
designates a parallel/serial conversion section that serially transmits a start bit, transmitted data and a parity bit. Numeral
204
designates a retransmission request signal generation circuit that generates a retransmission request signal and transmits the signal to the IC card
109
when received data has a parity error. Numeral
301
designates a transmission/reception switching section that switches between transmission and reception in communication with the IC card
109
. Numeral
302
designates a serial/parallel conversion section that receives the start bit, the data and the parity bit transmitted serially from the IC card
109
. Numeral
303
designates a parity check section that checks the parity of the received data and gives a notification to the retransmission request signal generation circuit
204
when there is a parity error. Numeral
304
designates a reception buffer that temporarily stores the received data until the data is read by the CPU
101
. Furthermore, numeral
1101
designates a pull-up resistor that switches the signal level of a data terminal (not shown) to High or Low.
Data reception at the conventional IC card reader/writer configured as described above will be described referring to FIG.
11
and FIGS.
12
(
a
) and
12
(
b
). FIGS.
12
(
a
) and
12
(
b
) show the formats of data transmitted from the IC card
109
.
During nontransmission, the data terminal of the IC card
109
holds a high impedance state, and its signal level is held High by the pull-up resistor
1101
. Data transmission of the IC card
109
is performed by using a character
1200
as one unit having 10 bits in total comprising a start bit
1201
having a Low signal level, data
1202
having 8 bits (Da, Db, Dc, Dd, De, Df, Dg and Dh) and a parity bit
1203
. The signal level of the parity bit
1203
is set Low when the calculated number of the high signal levels in the 8-bit data
1202
is even, and is set High when the number is odd. After the parity bit
1201
is transmitted, the data terminal is restored to its high impedance state. The signal level of the data terminal is held High by the pull-up resistor
1101
. On the other hand, the IC card reader/writer
1000
on the reception side compares the parity bit value calculated from the 8-bit received data
1202
with the value of the received parity bit
1203
. When the value of the parity bit
1203
is correct, the reception side prepares for the reception of the next data. When the value of the parity bit
1203
is not correct, it is judged that a parity error has occurred, and the signal level of the data terminal is set Low as an error signal in the period between 1 etu at the minimum and 2 etu at the maximum after the leading edge ((10.5±0.2) etu) of the start bit
1201
. At this time, an error signal
1220
is placed within a character protection period
1210
as shown in FIG.
12
(
b
). The transmission side checks the signal level of the data terminal after (11±0.2) etu from the start bit, and performs the following operation.
(A) When the signal level of the data terminal is High, it is judged that reception is performed properly. (B) When the signal level of the data terminal is Low, in other words, when the error signal
1220
is received, it is judged that transmission is not performed properly, and data retransmission is performed.
It is supposed that the IC card is usually carried and used by a user; however, since the data terminal of the IC card is exposed outside, the terminal is liable to be deteriorated by friction, corrosion, etc. and affected by dirt, moisture, static electricity, etc. Hence, the IC card reader/writer is requested to perform data transmission to and reception from the IC card properly and securely against these external disturbances.
Furthermore, in order that the IC card is widely used, it is necessary to attain functions for carrying out data transmission and reception properly and securely at low cost.
Hence, it is desired that the capacity of the reception buffer, which temporarily stores received data until the data is read by the CPU, is small. However, in the case when the reception buffer receives the next data when it cannot store more data (hereafter this case is referred to as a reception overrun), there is no other choice but to discard the received data or the data having already been stored in the reception buffer, whereby the CPU cannot read the received data properly. When the capacity of the reception buffer is small, this kind of reception overrun is apt to occur. When a reception overrun occurred conventionally at the reception time of the initial response of the IC card, it was necessary to reset the IC card and to receive all data again.
Moreover,
FIG. 13
shows the reception sampling timing for the data of one character on both the transmission side and the reception side. When the transmission rate on the transmission side differs from that on the reception side because a clock terminal (not shown in
FIG. 11
) undergoes the influence of noise or the like, differences occur between the content of 8-bit data
1302
on the side of transmitted data
1300
and the content of 8-bit data
1312
on the side of received data
1310
, and the content of the data cannot be received properly in some cases as shown in
FIG. 13
; this kind of error cannot be detected as a parity error. Conventionally, a function of detecting this kind of transmission error was not available; as a result, the reception side received wrong data from the IC card.
DISCLOSURE OF INVENTION
In consideration of these problems in the transmission and reception of data to and from the conventional IC card, the present invention is intended to provide an IC card reader/writer and method capable of securely receiving data even when the capacity of a reception buffer is small, capable of improving the detection rate of transmission errors occurring because of the influence of noise or the like, and thus capable of attaining more secure data transmission.
One aspect of the present invention is an IC card reader/writer and method comprising:
receiving means that receives data transmitted from an IC card in predetermined processing units,
a reception buffer that temporarily stores in predetermined processing units the data received by said receiving means,
a reception buffer state flag that is set when said reception buffer results in a state of being unable to store more data,
overrun detection means that detects an overrun in the case when said reception buffer state flag has been set and when said receiving means receives new data, and discards said new data having been received, and
retransmission request means that requests said IC card to retransmit data having the same content as that of said discarded data when at least said overrun is detected.
Accordingly, data transmitted from the IC card can be received securely,
Another aspect of the present invention is the IC card reader/writer, further comprising:
a PTS flag that is set only when said IC card can retransmit data in character units, wherein
said retransmission request means requests said IC card to retransmit said received data when said overrun has been detected and said PTS flag has been set.
Accordingly, data transmitted fr
Frech Karl D.
Le Uyen-Chau N.
RatnerPrestia
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