Alarm Management

SEMI E30
Sections:

4.3

Database Usage:

Documentation
Requirements:

You must document any defined Alarms, Collection Events, and VIDs associated with the Alarms.

V+ Task Usage:

Limits monitoring trace data collection.

 

See The Alarm Record Type for details on defining an alarm.

Alarms can to be set in the following ways:

  1. When a state in a user-defined state model is entered, the user can indicate that an alarm be trigger. The alarm to be triggered is defined by a State record type. See The State Record Type for details on specifying an alarm for a state transition.

  2. An AIM sequence may explicitly turn on an alarm. See the statement GENERATE_ALARM for details on setting an alarm using a statement. (See the statement CLEAR_ALARM for details on clearing an alarm using a statement.)

  3. A GEM variable can be monitored for a transition to an unsafe value. If this occurs, an alarm is triggered. (The system must be in the communicating state for this option.) See Automatic Alarm Detection below.

  4. The operator can set an alarm by choosing Force Alarm to Happen Now on the GEM Items database record for the desired alarm. See The Alarm Record Type.

  5. A user-written V+ routine can call the routine gm.alarm (alid, set)( ) to set an alarm. See gm.alarm for details.

After an alarm is set, the host will be notified (if reporting is enabled). Additionally, the alarm will be displayed on the GEM Control Panel (see GEM Control Panel, Establish Communication Options). If desired, an AIM sequence can be run (configured in the Alarm record type).

When the operator chooses the Clear Alarm button on the control panel (see GEM Control Panel, Establish Communication Options), it is assumed that the error condition has been corrected. The alarm is cleared automatically, and a clear acknowledgment is sent to the host (if reporting is enabled). If the alarm was initially triggered by a monitored variable, it is possible that the variable could still be in a bad condition. The alarm will not be triggered again unless there is a transition to a good zone and then back to a bad zone. Consider this carefully when designing alarms. An AIM sequence may be the only way to ensure proper factory safety requirements; on the other hand, this simple model may work well for things like monitoring an input signal and producing an alarm if it is turned on (or off).

NOTE: During AIM startup, any alarm that is found set (i.e., from a previous session) is automatically cleared (without notice).

Automatic Alarm Detection

Automatic alarm detection is set up by choosing Auto Alarm Detection on the GEM Variables database record that defines the variable to be monitored (see GEM Variables Database, Status Variable Using a V+ Variable). Automatic Alarm Detection shows the automatic alarm detection parameters that can be set when the alarm is enabled.

Figure 3-2. Automatic Alarm Detection

Variable ID shows the VID (from the GEM Variables database) that has been selected for monitoring. In Alarm ID, specify a defined alarm ID from the GEM Items database (this alarm will be triggered if a limit is exceeded). Set the lower and upper limits for the alarm and then select OK. While Alarm Enabled is checked (and the equipment is communicating and online), the variable is monitored automatically and compared with the limits specified. If a limit is reached, the actions specified in the Alarm database record for the Alarm ID will be triggered.

When setting the lower and upper limits for the alarm, the values must satisfy the following criteria:

Variable Minimum a3 Lower Limit a3 Upper Limit a3 Variable Maximum

The lower and upper limits for the alarm define a deadband between upper and lower zones. This deadband is considered in the same way as for limits monitoring requested by the host. See Section 4.2.4 of SEMI E30 for information on the processing of limits monitoring.

The data for automatic alarm detection are stored in the GEM Limits database, along with limits monitoring data from the host. Automatic alarm detection and limits monitoring can both be active for a variable at the same time. Also, automatic alarm detection can be active for any number of variables.

GEM Requirements

These GEM requirements are specified in Section 4.3.4 of SEMI E30:

  1. All alarms are user-defined with Alarm records in the GEM Items database, as described above.

  2. The enable/disable states of all alarms as well as the report definitions and collection events are stored in AIM databases on magnetic media.

  3. The alarm database contains fields for a description, a unique alarm identifier (ALID), alarm text (ALTX), the alarm status (ALCD), and collection event identifiers (CEID) for alarm-set and alarm-cleared events.

  4. Enabled alarm reports will be sent prior to corresponding enabled event reports.