Card system, IC card and card reader/writer used for the card system

A card system comprising an integrated circuit (IC) card having a port terminal to be electrically connected to a port terminal of a card reader/writer for transmitting and receiving data over a signal line between said IC card and said card reader/writer to read data from or write data to said IC card, said card system comprising:

• a data transmitting side, which is one of said IC card and said card reader/writer, transmitting a parity based upon content of the data together with the data over the signal line;
• a data receiving side, which is another of said IC card and said card reader/writer, checking whether or not there is any error in reception of data based upon content of the data and the parity received, said data transmitting side further transmitting back to the data transmitting side a data retransmission request signal for requesting the data transmitting side to retransmit the data to said data receiving side when an error in the reception of data is detected;
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• said IC card correcting a voltage level of said signal line to enable the data receiving side to request the data transmitting side to retransmit said data to the data receiving side, after the data receiving side transmits said data retransmission request signal to the data transmitting side, wherein transmission and reception of data over the signal line is enabled at a transmission rate for which voltage delay time on the signal line that corresponds to a predetermined voltage level for transmission and reception of data over the signal line exceeds data delay time that corresponds to input of data to be transmitted at the predetermined voltage over the signal line.

An integrated circuit (IC) card for use in a card system comprising a card reader/writer having a port terminal to be electrically connected to a port terminal port of said IC card for transmitting and receiving data over a signal line between said IC card and a card reader/writer to read data from or write data to said IC card, said card system comprising a data transmitting side, which is one of said IC card and said card reader/writer, for transmitting a parity based upon content of the data together with the data over the signal line, and a data receiving side, which is another of said IC card and said card reader/writer, for checking whether or not there is any error in reception of data based upon content of the data and the parity received, said data receiving side for further transmitting back to the data transmitting side a data retransmission request signal to request the data transmitting side to retransmit the data to said data receiving side when an error in the reception of data is detected, said IC card comprising:

• a means for correcting a voltage level of said signal line to enable the data receiving side to request the data transmitting side to transmit next data when it is verified that there is no error in the reception of said data based upon content of said data and said parity received by the data receiving side, wherein transmission and reception of data over the signal line is enabled at a transmission rate for which voltage delay time on the signal line that corresponds to a predetermined voltage level for transmission and reception of data over the signal line exceeds data delay time that corresponds to input of data to be transmitted at the predetermined level over the signal line.

An integrated circuit (IC) for use in a card system comprising a card reader/writer having a port terminal to be electrically connected to a port terminal of said IC card for transmitting and receiving data over a signal line between said IC card and a card reader/writer to read data from or write data to said IC card, said card system comprising a data transmitting side, which is one of said IC card and said card reader/writer, for transmitting a parity based upon content of the data together with the data over the signal line, and a data receiving side, which is another of said IC card and said card reader/writer, for checking whether or not there is any error in reception of data based upon content of the data and the parity received, said data receiving side further for transmitting back to the data transmitting side a data retransmission request signal to request the data transmitting side to retransmit the data to said data receiving side when an error in the reception of data is detected, said IC card comprising:

• a means for correcting a voltage level of said signal line to enable the data receiving side to request the data transmitting side to retransmit said data to the data receiving side, after the data receiving side transmits said data retransmission request signal to the data transmitting side, wherein transmission and reception of data over the signal line is enabled at a transmission rate for which voltage delay time on the signal line that corresponds to a predetermined voltage level for transmission and reception of data over the signal line exceeds data delay time that corresponds to input of data to be transmitted at the predetermined voltage level over the signal line.

A card system comprising an integrated circuit (IC) card and a card reader/writer, said IC card comprising at least a CPU, a memory for storing a program and/or data, a port terminal for data input and output, a terminal for receiving a clock signal, and a plurality of power supply terminals, said terminals being connected to said CPU of said IC card, said card reader/writer comprising at least a CPU, a port terminal for data input and output, a terminal for providing a clock signal, and a plurality of power supply terminals for supplying a power and a ground, said terminals being connected to said CPU of said card reader/writer, each of said terminals of said IC card to be elecirically connected to a corresponding terminal of said card reader/writer when said IC card is mounted on said card reader/writer, said card system comprising:

• a data transmitting side, which is one of said IC card and said card reader/writer, transmitting a data comprised of a series of data bits accompanied by an error chek code over a signal line arranged between said CPU of said IC card and said CPU of said card reader/writer through said port terminal of said IC card and said port terminal of said card reader/writer, said error check code calculated based on content of the data bits;
• a data receiving side, which is another of said IC card and said card reader/writer, checking for any error in reception of data by calculating an error check code based upon content of the data bits received and comparing the calculated error check code with said received error check code, said data receiving side further transmitting back to the data transmitting side a data retransmission request signal for requesting the data transmitting side to retransmit the data to said data receiving side when an error in the reception of data is detected;
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• said IC card comprising means for correcting a voltage level of said signal line to a predetermined voltage level, when it is verified by the data receiving side that there is no error in the reception of said data based upon said error check code, said correction of the voltage level of said signal line causing the data transmitting side to correctly detect that a data retransmission request signal from the data receiving side is not transmitted at a timing of inputting next data to said signal line by the data transmitting side, wherein transmission and reception of data over the signal line is enabled at a transmission rate for which voltage delay time on the signal line that corresponds to the predetermined voltage level for transmission and reception of data over the signal line exceeds data delay time that corresponds to input of data to be transmitted at the predetermined voltage level over the signal line.