| 摘要 |
An IC card having one-chip microcomputer (2), a memory (3) and an address bus (4) and a data bus (5) for coupling the microcomputer (2) and memory (3), all built in a card-shaped body. A plurality of terminals (12) for coupling microcomputer (2) to a terminal device are provided on the surface of the card. Microcomputer (2) includes a CPU 6, a timer (7), and an internal interrupt signal bus 8, through which the CPU 6 and timer (7) are coupled together. Timer (7) is always functioning during the operation of CPU 6 and includes a counter-register (13) for incrementing a count value and a timer control status register (14). The register (14) has an overflow flag (16) and interrupt enable flag (17). The overflow flag (16) is set by counter-register (13) when an overflow occurs in this register (13), and it is reset at a given timing by CPU 6. The interrupt enable flag (17) indicates the enable/disable of an internal interrupt for CPU 6, and is set or reset at a given timing by CPU 6. Overflow flag (16) and interrupt enable flag (17), which are coupled to an interrupt signal generator (18), are both set, an internal interrupt signal is sent to CPU 6 to generate an internal interrupt. Upon occurrence of the internal interrupt CPU 6 starts returning a processing result of a processing command to the external device.
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