In recent years, along with the popularization of portable information devices such as digital still camera and PDA, compact peripheral devices that can be used not only with personal computers but also in common with portable information devices such as digital still camera and PDA are drawing attention.
Main device and peripheral device of the conventional art 1 are disclosed in the Official Gazette of Japanese Unexamined Patent Publication Sho 62-217314. Main device and peripheral device of the conventional art 1 will be described with reference to FIG. 9.
FIG. 9 is a block diagram showing the configuration of main device having an I/O slot for connecting peripheral device in accordance with the conventional art 1. In FIG. 9, reference numeral 901 denotes a main device. Main device 901 has a control section 902, a plurality of I/O slots 903-906, and reed relays 907-910 which are located at the connecting section of the power supply wiring of I/O slots 903-906 respectively. Peripheral devices of the conventional art 1 which are inserted in I/O slots 903-906, are supplied power from main device 901. Main device 901 opens and closes reed relays 907-910 respectively by program control. By opening and closing reed relays 907-910 respectively, I/O slots 903-906 can individually switch ON/OFF each power supply which is to be supplied to the inserted peripheral devices. Main device 901 can reduce its power consumption by switching off the power supply of peripheral device which is inserted in an I/O slot but needs not to operate.
Peripheral device of the conventional art 2 is disclosed in the Official Gazette of Japanese Unexamined Patent Publication 2001-209764. Peripheral device of the conventional art 2 is an IC card. Peripheral device of the conventional art 2 automatically selects a high internal clock in a case where main device is a stationary type apparatus, and automatically selects a low internal clock in a case where main device is a battery-operated type apparatus.
However, the higher the function of peripheral device becomes, the massive the scale of its circuit becomes, and hence power consumption of a single peripheral device increases. In such cases, there was a problem in which power control would be insufficient when main device of the conventional art 1 which has only the function to switch ON or OFF the power supply in unit of individual peripheral device.
Furthermore, multifunctional peripheral devices have come on the market recently, and there would be a problem in which the entire circuit of peripheral device would operate even in a case where there is a function that is not in use, and hence consumes unnecessary power, when main device of the conventional art 1 is used.
When main device which is a power supply source, is a device that operates on a limited power such as a portable information device and the like, the above-mentioned power consumption issue was much serious.
Peripheral device of the conventional art 2 can change the internal clock corresponding to the main device. An IC card of the conventional art 2 can effectively reduce power consumption when the card is connected to a specific main device. However, for example in regard to IC cards (peripheral device) that were standardized throughout the industry which includes a number of manufacturers, IC cards having various functions are manufactured, and each IC card may be connected to a wide variety of main devices. Depending on an IC card, there is a case where a factor suitable for reducing power of an IC card is a factor other than an internal clock. Depending on an IC card, there is a case where an internal clock cannot be changed. Even when main device is a battery-operated type, there is a case where IC card requires to work at a high-speed internal clock. Main device and peripheral device of the conventional art 2 had difficulty in appropriately controlling power in peripheral devices and main devices that are the connecting counterparts of main devices and peripheral devices, which were not envisioned when that main device and peripheral device were commercialized.
The present invention, in regard to connection with an arbitrary main device, aims to provide a peripheral device, control method thereof, and program thereof, in which the peripheral device does not consume unnecessary power by corresponding to suppliable electric power of the main device.
The present invention, in regard to connection with an arbitrary main device, aims to provide a peripheral device, control method thereof, and program thereof, in which the peripheral device automatically sets to the most appropriate environment by corresponding to functions and the like of the main device, for example giving priority to performance or giving priority to power consumption.
The present invention, in regard to connection with an arbitrary peripheral device, aims to provide a main device and control method thereof, in which the main device automatically sets the peripheral device to the most appropriate environment by corresponding to functions and the like of the peripheral device, for example giving priority to performance or giving priority to power consumption.
The present invention, in regard to connection with an arbitrary peripheral device, aims to provide main device and control method thereof, in which the main device lowers unnecessary power consumption of peripheral device by corresponding to suppliable electric power of main device.