| 摘要 |
A system realize power saving of a portable information processing unit including an external device, when the external unit receiving the power supplied from the portable information processing unit is connected to the portable information processing unit. An operation mode according to the power supply state of the external unit is set into the portable information processing unit, and the external device is informed of the set operation mode, according to the power supply state. When data processing is in execution also in the external device upon request from the portable information processing unit, even when the operation mode change information is received, the mode change is awaited until the completion of the processing of the external device. Thus, by changing the operation mode, low-power consumption operation including the external device can be realized without impeding the operation in the external device.
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