To make a plurality of microcomputers move to and return from a power-saving mode cooperatively.
When a slave microcomputer 120 of a liquid crystal display part 12 has a factor of moving to the power-saving mode, that is reported to a master microcomputer 110 of a control box 11 through a communication line. When a factor of moving to the power-saving mode has occurred in the master microcomputer 110 or it receives the report, the master microcomputer 110 sends a request to move to the power-saving mode to the slave microcomputer 120 and moves to the power-saving mode. The slave microcomputer 120 having received the moving request also moves to the power-saving mode. The master microcomputer 110 or slave microcomputer 120 where a factor of returning has occurred, returns from the power-saving mode and sends a request to return to the opposite side by using an interruption signal line 132, so that the opposite side also returns from the mode.
NEHASHI AKIRA
UEHARA KOICHI
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