| 摘要 |
<p>PROBLEM TO BE SOLVED: To grasp the on/off state of the power of a peripheral processor by permitting a host computer to request the current state information of a peripheral devices after it receives the state information from the peripheral devices. SOLUTION: When a user turns off the power switch of a printer 20 during use, it is detected that power voltage drops to the value of not more than a prescribed reference value before it becomes zero. The automatic state information notice ASB of a restoration impossible error is informed to a host 10. The host 10 receives it, transmits a real time command to the printer 20 after prescribed time and requests the current state information of the printer 20. Since the power of the printer 20 becomes operation impossible voltage when the command is transmitted from the host 10, the printer 20 cannot receive the command. The host 10 judges that the power of the printer 20 is turned off when a response is not given from the printer 20 within prescribed time until the response is given after the command is transmitted.</p> |
