| 摘要 |
PROBLEM TO BE SOLVED: To protect a device on an optional board, when only a power supply to be supplied to the option board is turned off by disconnecting the system bus signals of the option board, so as not to make the power supply on/off of the respective option boards connected to a system bus affect a bus operation in the case of entering a power-saving mode. SOLUTION: When the power supply A is kept on and the power supply B is turned off so as to attain a power saving mode, input/output devices IC4-IC6 are supplied with power from the power supply A. However, since a high imprudence state is attained, the input/output device of a FAX 448 as the option board is disconnected from the system bus. In this state, the power supply B is prevented from being supplied to the input/output device of the FAX 448 as the option board in an off state. As a result, an inconvenience which invites damagings the input/output device of the FAX 448 is avoided. Thus, the device on the option board is protected. |
