| 摘要 |
<p>PURPOSE:To detect the turn-on/turn-off state of a power source of a peripheral equipment and a connecting state of a cable by reading in an output signal of a monostable multivibrator, and discriminating a level of its output signal. CONSTITUTION:An output of a crystal oscillator 4 is brought to frequency division to a triggerable frequency by a monostable multivibrator 5, and a signal CLK is obtained. Subsequently, AND 6 of the CLK signal and an enable signal from a CPU 2 is taken and an SYSN signal is sent out to a peripheral equipment 11 side. When a power source of the equipment 11 is turned on, a monostable multivibrator 12 of the equipment 11 side is triggered, and an output pulse is outputted. The monostable multivibrator 12 is retriggered, and while a trigger pulse SYNC is inputted, its output 'STATE' remains a 'Low' level. The CPU 2 of a computer 1 side reads in this 'STATE' signal, and in the case of the 'Low' level, it can be confirmed that the power source of the equipment 11 is turned on, and a cable 16 is also connected normally. In the case of the 'High' level, it is decided that the power source of the equipment 11 is turned off, or the cable 16 is not connected yet.</p> |
