ARITHMETIC UNIT AND ARITHMETIC PROCESSING METHOD FOR OPERATING WITH HIGHER AND LOWER CLOCK FREQUENCIES

There is a need for providing a battery-less integrated circuit (IC) card capable of operating in accordance with a contact usage or a non-contact usage, preventing coprocessor throughput from degrading despite a decreased clock frequency for reduced power consumption under non-contact usage, and ensuring high-speed processing under non-contact usage. A dual interface card is a battery-less IC card capable of operating in accordance with a contact usage or a non-contact usage. The dual interface card operates at a high clock under contact usage and at a low clock under non-contact usage. A targeted operation comprises a plurality of different basic operations. The dual interface card comprises a basic arithmetic circuit group. Under the contact usage, the basic arithmetic circuit group performs one basic operation of the targeted operation at one cycle. Under the non-contact usage, the basic arithmetic circuit group sequentially performs at least two basic operations of the targeted operation at one cycle.