In a monitor apparatus for a sequential-function-chart-type programmable controller, a standard value of an active time of an arbitrary step in a sequential-function-chart program is stored, and the active time of the arbitrary step is measured during execution of the program. An anomalous state of the...http://www.google.com/patents/US6859898?utm_source=gb-gplus-sharePatent US6859898 - Monitor apparatus for sequential-function-chart-type programmable controller
