Portable electronic device having an external I/O unit and power source integral therewith

摘要

An IC card reader-writer is integrated with a battery pack 15. This IC card reader-writer 16 has a control terminal CNT and a power supply control switch 30. A portable phone unit sends power-on/off signals, which are received by the control terminal CNT to turn on and off the power supply control switch 30 to control power supply from the battery 18 to the IC card reader-writer 16. The CPU 24 of the IC card reader-writer 16 controls power supply in such a manner that power is supplied to the IC card 22 only when access to the IC card 22 is necessary and stopped when access to the IC card 22 is unnecessary.