| 摘要 |
<p>PURPOSE:To previously and optionally program the state of an external output terminal immediately after the rise of a power supply or at the time of occurring power failure by providing the output interface with a switching circuit for alternatively outputting an external output signal from a normal output circuit and an external output signal from an emergency external output circuit to an external output terminal. CONSTITUTION:A data latch circuit 17 and an output transistor (TR) 18 constitute the normal output circuit and the circuit 17 latches output data on a data bus synchronously with the rise of a latch circuit 19. A data latch circuit 21 and an output TR 22 constitute the emergency output circuit and the circuit 21 latches the state of an initial output setting part 23 synchronously with the rise of a reset signal 24. When a relay coil 28 is excited, a signal is outputted from the normal output circuit to the external output terminal 31, and when the coil 28 is deexited, a signal is outputted from the emergency output circuit to the terminal 31. Thereby, the state of the external output terminal 31 can be optionally controlled in accordance with set contents of the setting part 23 immediately after the rise of the power supply, at the time of occurring power failure, or at the time of runaway of the microprocessor.</p> |
