MODE DETECTION METHOD FOR HOT BACK-UP APPARATUS

摘要

A mode detection method of a hot back up device changes a mode state transition structure to three modes. By an interrupt of a mode detection controller inside of the hot back up device, a CPU discriminates a status data. The mode detection method informs a main CPU of a self-operation toward a corresponding mode, and gives a mode detection controller a command in order to make a mode detection pulse output of a frequency pulse corresponding to an active mode. Accordingly, the mode detection method stably and quickly detects a main CPU error or another malfunction in a double system of a programmable logic controller(PLC).