Control device, image forming apparatus, and control method

A control method comprising:

• storing, in a second interruption information memory included in a second sub-controller, second interruption information output from one or more second devices that are connected to the second sub-controller;
• transmitting, from a second interruption controller included in the second sub-controller, an interruption signal upon storing of the second interruption information in the second interruption information memory, and reading and transmitting the second interruption information stored in the second interruption information memory from the second interruption controller;
• transmitting a synchronization signal that is synchronous with the interruption signal from a synchronization signal generator included in the second sub-controller;
• storing, in a first interruption information memory included in a first sub-controller, first interruption information output from one or more first devices that are connected to the first sub-controller, and the second interruption information transmitted from the second sub-controller;
• transmitting, from a first interruption controller included in the first sub-controller, the interruption signal received from the second sub-controller, and reading and transmitting the first interruption information and the second interruption information stored in the first interruption information memory from the first interruption controller;
• and
• controlling, in a synchronization signal controller included in the first sub-controller, a storage operation of the first interruption information memory in accordance with the synchronization signal, wherein
• the first sub-controller and the second sub-controller are controlled by a master controller,
• the master controller and the first sub-controller are connected to each other by a full-duplex serial bus,
• the first sub-controller and the second sub-controller are connected to each other by a full-duplex serial or parallel bus,
• the interruption signal is transmitted from the second sub-controller to the first sub-controller by using a unidirectional transmission line, and
• the synchronization signal is transmitted from the second sub-controller to the first sub-controller by using another unidirectional transmission line.