| 摘要 |
PURPOSE:To realize the prevention of malfunction at the power supply failure very easily, by providing a power supply failure detecting means which is operated with the 2nd power supply output generated from the 2nd power supply unit different from the 1st power supply unit and generates a power failure signal, when the output of a termination resistor and the 2nd power supply is interrupted to a drive signal. CONSTITUTION:The power failure detecting means 14 consists of a resistor, which is the same module resistor as the termination resistor 13. The module resistor is not provided for reception circuits 2', 3', but mounted on a reception circuit 4' only placed at the remotest terminal. It is assumed that a power supply unit 12 is failed, when the drive signal (a) on an interface is an ineffective polarity (high level). Then the drive signal (a) is inverted to a low level (effective polarity) unconditionally. Since a power failure signal (b) is on a low level at the same time regardless of the inversion, reception gate output signals h', i' outputted from reception gates 6', 7' are not the effective polarity. |
