US Patent RE40147 Memory card device including a clock generator

Disclosed herein is a card having a controller and a clock control circuit. The controller incorporates a core logic, and the clock control circuit incorporates a PLL. When a card becomes idle to wait for commands, the clock control circuit stops the supply of a clock signal to the core logic. The clock control circuit can operate in two clock control modes. In the first clock control mode, the circuit stops the PLL. In the second clock control mode, the circuit shuts off the clock signal to be supplied from the PLL to the controller.