PURPOSE: To minimize the number of signal lines of the interface between a measuring instrument and a digital meter by providing a power-on reset circuit.
CONSTITUTION: This device is constituted of a microprocessor unit(MPU) 2 connected to a measuring instrument having the serial communication function and incorporated with the serial communication interface and a display device 3 and a transmitter 4, and is provided with a power-on circuit 5. The power-on circuit 5 outputs a reset signal to the MPU 2 and initializes it when the power is first supplied to a digital meter 1. When the MPU 2 runs away during the operation, the power supply is stopped, then a reset signal is outputted from the power-on reset circuit 5 to initialize the MPU 2. Thus, it is unnecessary to connect the reset signal from the measuring instrument to the digital meter 1. The presence or absence of the runaway of the MPU 2 is judged by the presence or absence the response of the digital meter 1 for the data transmitted from the measuring instrument and the abnormality of response data.
OKABE NORITOSHI
KOBAYASHI TERUO
HITACHI INSTRUMENTS ENG