Semiconductor integrated circuit and noncontact information system including it
First Claim
1. A semiconductor integrated circuit, to which a power supply voltage is supplied via electromagnetic waves received by an antenna coil, and which exchanges data via the antenna coil, the semiconductor integrated circuit comprising:
- a memory circuit storing data;
a pair of terminals to which the antenna coil is connected;
a modulating-transmitting circuit for transmitting data via the antenna coil by varying a load between the terminals according to data to be transmitted;
a transmission control circuit for outputting data stored in the memory circuit to the modulating-transmitting circuit; and
a reset signal generating circuit for outputting a reset signal for resetting the transmission control circuit to the transmission control circuit when the power supply voltage decreases below a predetermined threshold value, wherein;
the transmission control circuit is configured to output a transmission status signal, which indicates that data is being transmitted; and
the reset signal generating circuit is configured so that the threshold value is lower during a period in which the transmission status signal is being output than during a period in which the transmission status signal is not being output.
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Accused Products
Abstract
The present invention extends the reading range between a contactless type information medium (semiconductor integrated circuit) and a reader/writer, which exchanges data in contactless communications with the contactless type information medium, and enables a stable data exchange even if the power supply voltage is lowered when data is returned from the contactless type information medium to the reader/writer. Specifically, when data is returned from the contactless type information medium, the data to be returned is held in the logic circuit section 200 capable of operating at a lower voltage than the non-volatile memory circuit section 300, and the reset detection lower limit voltage to be used by the reset generating circuit 160 during the data-returning period is set to be lower than that during periods other than the data-returning period.
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Citations
15 Claims
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1. A semiconductor integrated circuit, to which a power supply voltage is supplied via electromagnetic waves received by an antenna coil, and which exchanges data via the antenna coil, the semiconductor integrated circuit comprising:
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a memory circuit storing data;
a pair of terminals to which the antenna coil is connected;
a modulating-transmitting circuit for transmitting data via the antenna coil by varying a load between the terminals according to data to be transmitted;
a transmission control circuit for outputting data stored in the memory circuit to the modulating-transmitting circuit; and
a reset signal generating circuit for outputting a reset signal for resetting the transmission control circuit to the transmission control circuit when the power supply voltage decreases below a predetermined threshold value, wherein;
the transmission control circuit is configured to output a transmission status signal, which indicates that data is being transmitted; and
the reset signal generating circuit is configured so that the threshold value is lower during a period in which the transmission status signal is being output than during a period in which the transmission status signal is not being output. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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Specification