Patent ID: 8176348

Claim:
A control device comprising: a main control unit that serves as a main component for device control and to which power is supplied from a first power unit; a power control unit that controls the first power unit and to which power is supplied from a second power unit independent from the first power unit; a memory control unit that accesses a memory that stores therein a computer program and data, the memory control unit being supplied with power from the second power unit; and a network control unit that receives packets through a network and performs packet filtering and to which power is supplied from the second power unit, wherein when the main control unit instructs the power control unit to shift from a normal mode to a power saving mode, the power control unit controls the first power unit to turn off power from the first power unit to the main control unit, the network control unit transfers the packet, which has been accepted by the packet filtering, by a direct memory access through the memory control unit to the memory to cause the memory to store the packet, and determines whether the accepted packet is of a predetermined type to send a signal indicative of reception of the packet of the predetermined type to the power control unit, during the power saving mode, and the power control unit, when the power control unit receives the signal indicative of reception of the packet of the predetermined type from the network control unit, controls the first power unit to turn on power from the first power unit to the main control unit to return the first power unit from the power saving mode to the normal mode, and then the main control unit reads the packet that has been transferred from the network control unit and stored in the memory during the power saving mode, and processes the read packet.