Understanding Alarm Statuses

iFIX can process alarm status information from I/O drivers. This information complements the alarms generated by iFIX database blocks. When an alarm is returned from a driver, iFIX compares the driver alarm against the block alarm. The alarm with the higher severity is used as the block alarm and the other alarm is ignored.

NOTE: As of iFIX 4.5, only the alarm statuses IA_OK and IA_COMM are supported for use through the SM2 driver.

iFIX defines the following alarms with the following severity:

Severity	Alarm Status	Description
16 (highest)	IA_COMM	Communication error ("BAD" value).
16 (highest)	IA_IOF	General I/O failure.
16 (highest)	IA_OCD	Open circuit.
16 (highest)	IA_URNG	Under range (clamped at 0).
16 (highest)	IA_ORNG	Over range (clamped at MAX).
16 (highest)	IA_RANG	Out of range (value unknown).
16 (highest)	IA_DEVICE	Device failure.
16 (highest)	IA_STATION	Station failure.
16 (highest)	IA_ACCESS	Access denied (privilege).
16 (highest)	IA_NODATA	On poll, but no data yet.
16 (highest)	IA_NOXDATA	Exception item, but no data yet.
16 (highest)	IA_MANL	Special code for MANL/MAINT (for inputs).
8	IA_FLT	Floating point error.
8	IA_ERROR	General block error.
8	IA_ANY	Any block alarm.
8	IA_NEW	New block alarm.
7	IA_HIHI	The block is in the HIHI alarm state (High High).
7	IA_LOLO	The block is in the LOLO alarm state (Low Low).
7	IA_COS	Change of state.
7	IA_CFN	Change From Normal (Digital block only).
7	IA_TIME	Time-out alarm.
7	IA_SQL_LOG	Not connected to database.
6	IA_HI	The block is in the HI alarm state (High).
6	IA_LO	The block is in the LO alarm state (Low).
6	IA_RATE	Value exceeds rate of change setting since last scan period.
6	IA_SQL_CMD	SQL command not found or invalid.
5	IA_DEV	Deviation from the set point.
5	IA_DATA_MATCH	SQL command does not match data list.
4	IA_FIELD_READ	Error reading tag values.
4	IA_FIELD_WRITE	Error writing tag values.
1	IA_DSAB	Alarms disabled.
0 (lowest)	IA_OK	The block is in normal state.

Using the preceding table, you can see that if a driver returns a HIHI alarm to a block that is in HI alarm, iFIX changes the alarm state to HIHI because the driver alarm is more severe. However, if the alarms are of equal severity, iFIX does not change the alarm state of the block. For example, if the block is in HI alarm and the driver returns a LO alarm, the block's alarm state does not change because both alarms have equal severity. Once an operator acknowledges the HI alarm, iFIX changes the block's alarm state.

NOTE: If you set a communication error to the S register with the SetCommError function, then all SM2 registers show a COMM alarm status. When examining the alarm status of text, only the status of the first character (byte) is read. You can control the alarm status functions of the SM2 driver using its C API only. Refer more information about this API, refer to the Using the SM2 C API section.

See Also