Introduction

Some project variables can be configured as alarms. This means associating the display of a text on the HMI to the status of the selected variables. The text tells the operator what is happening on the system.The process variables displayed can be either of two states:

• FALSE (0) alarm inactive
• TRUE (1) alarm active

For this reason, only BOOL variables can be configured as alarms because, by definition, they can assume only the values of false and true.On the rising edge FALSE TRUE of the variable associated with the alarm, the monitor displays a text corresponding to the cause.On the falling edge TRUE FALSE, the associated text does not disappear automatically, so that the alarm acknowledge procedure can begin.We will now define the acknowledge procedures.Every alarm could be set in a way, that his acknowledgement will be automatic (auto ack); in this case, for example, the alarm text will appear and disappear automatically from the page devoted to the display of active alarms only when the value of the associated variable changes.