Patent ID: 8635479

Claim:
An apparatus for controlling transition between a normal operation mode and a power save mode of the apparatus, the apparatus comprising: a main controller to control entire system of the apparatus in the normal operation mode; and a sub controller to control a selected portion of the entire system of the apparatus in the power save mode, wherein the sub controller is further configured to: determine whether a power save mode transition condition is satisfied, the power save mode transition condition defining a condition under which the normal operation mode is to be switched to the power save mode; send a transition notification to the main controller when the power save mode transition condition is satisfied and begin a transition to the power save mode, wherein, during a specified time period, when the transition to the power save mode is interrupted for one of the main controller or the sub controller, a cancellation notification is sent to another one of the main controller or the sub controller, and the transition to the power save mode for each of the main controller and the sub controller is cancelled.