Generally, an image processor, such as a printer, scanner, fax machine, copier, and multifunctional peripheral (MFP) combining functions of those equipments, has a communication unit (NIC (Network Interface Card), modem (Modulator-Demodulator), etc.) that communicates with an external apparatus (computer, another image processor, etc.) via a communication medium such as a network and telephone circuit. Such an image processor may have a function of changing its operation state to a power-saving state (generally called sleep mode), where the processor consumes less power than power consumed in a regular operation state, when a given sleep condition is satisfied in the regular operation state.
The sleep condition, for example, includes a condition that an operation input unit incorporated into the image processor has received no operation input and the processor has received no data from an external apparatus through the communication unit for a given time or longer. The sleep condition may also include a condition that the present time is in a time zone that is set in a predetermined time schedule (e.g., weekly schedule).
For example, Japanese Laid-Open Patent Publication No. 2005-172869 discloses a digital MFP that has a weekly timer function of turning on and off the power supply for the MFP according to a predetermined weekly schedule. This function allows the image processor to automatically change its operation state into an energy-saving state in a time zone where a possibility of use of the image processor is extremely low, such as nighttime and holiday, and to automatically return to a regular operation state in other time zones. As a result, the image processor becomes capable of saving more power.
In another example, Japanese Laid-Open Patent Publication No. 2000-092254 discloses a fax machine that appoints a time and that transmits predesignated image data by fax when the appointed time has come. Hereinafter, such a function of appointing a scheduled time for executing a job (such as data transmission process) and executing the job at the scheduled time is called a job reservation function. An image processor having this job reservation function executes a job not particularly urgent in avoidance of a time of load concentration or executes such a job at a time of lower power cost, thus offers great convenience.
An image processor has a controlling unit that controls various devices of the processor. This controlling unit (usually a main controlling unit that assumes overall control over the entire part of the processor) controls energization of each device, thus controlling transfer to the energy-saving state and return to a regular state from the energy-saving state. The job reservation function is also realized by the controlling unit of the image processor.
The image processor so structured as to cause the controlling unit to realize the job reservation function, however, must keep the multifunctional controlling unit energized even in the energy-saving state, which poses a problem of difficulty in achieving a sufficient energy-saving effect.
Meanwhile, even when the image processor is in the energy-saving state, the communication unit (NIC, etc.) should desirably be kept energized so that the image processor at least sends back any form of reply in response to a given request, such as printing request, from an external apparatus. This is because of a necessity for preventing a user from having a wrong idea that the image processor is developing trouble.