| 摘要 |
PURPOSE:To hold an internal input data when the output of a process input/ output device is cut off and to improve both accuracy and reliability, by delivering a digital signal obtained by adding a prescribed timing signal to the output signal of a central processor. CONSTITUTION:A 1-bit timing signal is added to a digital signal of a prescribed bit which is delivered from a central processor 2 to obtain a digital signal. A means is provided to deliver the obtained digital signal and at the same time to deliver another new digital signal from a process input/output device based on the detection of a timing signal. For instance, a digital data is obtained by adding the 1-bit timing signal to a digital data of 12 bits obtained as an arithmetic result of the processor 2 from a process controller 3c of a digital controller 1. The obtained digital data is delivered to an analog back-up circuit 4c, and the circuit 4c detects the timing signal. Then the circuit 4c performs a D/A conversion to change the 12-bit data into an internal input data to carry out a back-up operation. The output of this back-up operation is delivered as a control signal. |
