| 摘要 |
A portable communication device such as a mobile telephone (20, fig 2) or portable information processing terminal (e.g. PDA), having at least a main controller 201 and a sub controller 202, where the sub controller 202 is for controlling external communication, reduces power consumption by powering down the sub controller 202 when it is determined that external communication has not occurred for a predetermined time-out period. The external communication may be wireless radio communication, e.g. for location registration, or wired communication with an external information processing device (212, fig 2), e.g. a cable connected PC. In operation, the main controller or CPU 201 starts a time-out timer and sends an operation check request to the sub controller/CPU 202 to check whether the sub controller 202 is performing external communication. If an operation check response indicative of external communication is received from the sub CPU 202 before expiry of the time-out period, the sub CPU 202 remains powered on. If the operation check response is not received before the time-out period or there is no operation check response, due to there either being no external communication or their being a failure in the transmission/reception of the operation check requests or responses (see figs 5-11), the sub controller is powered down. |
