Merge lp:~khkim/epics-base/alarm-filter into lp:~epics-core/epics-base/3.14

[Kim, Kukhee]

This branch has alarm filter for ai, calc, longin, and mbbi record types.

[Ralph Lange (ralph-lange)]

I can easily see this for the "numerical" calc and the longin records.
But what does the new behavior for the "enum" mbbi record mean? Suppressing spikes? How does that interact with the ACKT field?

[Andrew Johnson (anj)]

Merged into my record-updates branch which will go into 3.15 soon.

review: Approve

=== modified file 'src/rec/aiRecord.c'
--- src/rec/aiRecord.c	2010-04-05 18:49:18 +0000
+++ src/rec/aiRecord.c	2010-05-28 09:22:29 +0000
@@ -6,7 +6,7 @@
 * EPICS BASE is distributed subject to a Software License Agreement found
 * in file LICENSE that is included with this distribution. 
 \*************************************************************************/
-/* $Id$ */
+/* $Id: aiRecord.c,v 1.20.2.6 2009/04/03 14:40:12 lange Exp $ */
 
 /* aiRecord.c - Record Support Routines for Analog Input records */
 /*
@@ -41,6 +41,9 @@
 #undef  GEN_SIZE_OFFSET
 #include "epicsExport.h"
 
+/* Hysterisis for alarm filtering: 1-1/e */
+#define THRESHOLD 0.6321
+
 /* Create RSET - Record Support Entry Table*/
 #define report NULL
 #define initialize NULL
@@ -99,7 +102,7 @@
 extern unsigned int     gts_trigger_counter;
 */
 
-static void checkAlarms(aiRecord *prec);
+static void checkAlarms(aiRecord *prec, epicsTimeStamp *lastTime);
 static void convert(aiRecord *prec);
 static void monitor(aiRecord *prec);
 static long readValue(aiRecord *prec);
@@ -158,12 +161,15 @@
 	aidset		*pdset = (aidset *)(prec->dset);
 	long		 status;
 	unsigned char    pact=prec->pact;
+        epicsTimeStamp	 timeLast;
 
 	if( (pdset==NULL) || (pdset->read_ai==NULL) ) {
 		prec->pact=TRUE;
 		recGblRecordError(S_dev_missingSup,(void *)prec,"read_ai");
 		return(S_dev_missingSup);
 	}
+        timeLast = prec->time;
+
 	status=readValue(prec); /* read the new value */
 	/* check if device support set pact */
 	if ( !pact && prec->pact ) return(0);
@@ -174,7 +180,7 @@
 	else if (status==2) status=0;
 
 	/* check for alarms */
-	checkAlarms(prec);
+	checkAlarms(prec,&timeLast);
 	/* check event list */
 	monitor(prec);
 	/* process the forward scan link record */
@@ -283,60 +289,114 @@
     return(0);
 }
 
 
-static void checkAlarms(aiRecord *prec)
+static void checkAlarms(aiRecord *prec, epicsTimeStamp *lastTime)
 {
-    double val, hyst, lalm;
-    double alev;
+    enum {
+        range_Lolo = 1,
+        range_Low,
+        range_Normal,
+        range_High,
+        range_Hihi
+    } alarmRange;
+    static const epicsEnum16 range_stat[] = {
+        SOFT_ALARM, LOLO_ALARM, LOW_ALARM,
+        NO_ALARM, HIGH_ALARM, HIHI_ALARM
+    };
+    double val, hyst, lalm, alev, aftc, afvl;
     epicsEnum16 asev;
 
     if (prec->udf) {
         recGblSetSevr(prec, UDF_ALARM, INVALID_ALARM);
+        prec->afvl = 0;
         return;
     }
 
-    val = prec->val;
+    val  = prec->val;
     hyst = prec->hyst;
     lalm = prec->lalm;
 
-    /* alarm condition hihi */
-    asev = prec->hhsv;
-    alev = prec->hihi;
-    if (asev && (val >= alev || ((lalm == alev) && (val >= alev - hyst)))) {
-        if (recGblSetSevr(prec, HIHI_ALARM, asev))
-            prec->lalm = alev;
-        return;
-    }
-
-    /* alarm condition lolo */
-    asev = prec->llsv;
-    alev = prec->lolo;
-    if (asev && (val <= alev || ((lalm == alev) && (val <= alev + hyst)))) {
-        if (recGblSetSevr(prec, LOLO_ALARM, asev))
-            prec->lalm = alev;
-        return;
-    }
-
-    /* alarm condition high */
-    asev = prec->hsv;
-    alev = prec->high;
-    if (asev && (val >= alev || ((lalm == alev) && (val >= alev - hyst)))) {
-        if (recGblSetSevr(prec, HIGH_ALARM, asev))
-            prec->lalm = alev;
-        return;
-    }
-
-    /* alarm condition low */
-    asev = prec->lsv;
-    alev = prec->low;
-    if (asev && (val <= alev || ((lalm == alev) && (val <= alev + hyst)))) {
-        if (recGblSetSevr(prec, LOW_ALARM, asev))
-            prec->lalm = alev;
-        return;
-    }
-
-    /* we get here only if val is out of alarm by at least hyst */
-    prec->lalm = val;
-    return;
+    /* check VAL against alarm limits */
+    if ((asev = prec->hhsv) &&
+        (val >= (alev = prec->hihi) ||
+         ((lalm == alev) && (val >= alev - hyst))))
+        alarmRange = range_Hihi;
+    else
+    if ((asev = prec->llsv) &&
+        (val <= (alev = prec->lolo) ||
+         ((lalm == alev) && (val <= alev + hyst))))
+        alarmRange = range_Lolo;
+    else
+    if ((asev = prec->hsv) &&
+        (val >= (alev = prec->high) ||
+         ((lalm == alev) && (val >= alev - hyst))))
+        alarmRange = range_High;
+    else
+    if ((asev = prec->lsv) &&
+        (val <= (alev = prec->low) ||
+         ((lalm == alev) && (val <= alev + hyst))))
+        alarmRange = range_Low;
+    else {
+        alev = val;
+        asev = NO_ALARM;
+        alarmRange = range_Normal;
+    }
+
+    aftc = prec->aftc;
+    afvl = 0;
+
+    if (aftc > 0) {
+        /* Apply level filtering */
+        afvl = prec->afvl;
+        if (afvl == 0) {
+            afvl = (double)alarmRange;
+        } else {
+            double t = epicsTimeDiffInSeconds(&prec->time, lastTime);
+            double alpha = aftc / (t + aftc);
+
+            /* The sign of afvl indicates whether the result should be
+             * rounded up or down.  This gives the filter hysteresis.
+             * If afvl > 0 the floor() function rounds to a lower alarm
+             * level, otherwise to a higher.
+             */
+            afvl = alpha * afvl +
+                   ((afvl > 0) ? (1 - alpha) : (alpha - 1)) * alarmRange;
+            if (afvl - floor(afvl) > THRESHOLD)
+                afvl = -afvl; /* reverse rounding */
+
+            alarmRange = abs((int)floor(afvl));
+            switch (alarmRange) {
+            case range_Hihi:
+                asev = prec->hhsv;
+                alev = prec->hihi;
+                break;
+            case range_High:
+                asev = prec->hsv;
+                alev = prec->high;
+                break;
+            case range_Normal:
+                asev = NO_ALARM;
+                break;
+            case range_Low:
+                asev = prec->lsv;
+                alev = prec->low;
+                break;
+            case range_Lolo:
+                asev = prec->llsv;
+                alev = prec->lolo;
+                break;
+            }
+        }
+    }
+    prec->afvl = afvl;
+
+    if (asev) {
+        /* Report alarm condition, store LALM for future HYST calculations */
+        if (recGblSetSevr(prec, range_stat[alarmRange], asev))
+            prec->lalm = alev;
+    } else {
+        /* No alarm condition, reset LALM */
+        prec->lalm = val;
+    }
 }
 
 
 static void convert(aiRecord *prec)
 
=== modified file 'src/rec/aiRecord.dbd'
--- src/rec/aiRecord.dbd	2005-11-15 23:35:34 +0000
+++ src/rec/aiRecord.dbd	2010-05-28 09:22:29 +0000
@@ -138,6 +138,11 @@
 		promptgroup(GUI_ALARMS)
 		interest(1)
 	}
+	field(AFTC,DBF_DOUBLE) {
+		prompt("Alarm Filter Time Constant")
+		promptgroup(GUI_ALARMS)
+		interest(1)
+	}
 	field(ADEL,DBF_DOUBLE) {
 		prompt("Archive Deadband")
 		promptgroup(GUI_DISPLAY)
@@ -153,6 +158,11 @@
 		special(SPC_NOMOD)
 		interest(3)
 	}
+	field(AFVL,DBF_DOUBLE) {
+		prompt("Alarm Filter Value")
+		special(SPC_NOMOD)
+		interest(3)
+	}
 	field(ALST,DBF_DOUBLE) {
 		prompt("Last Value Archived")
 		special(SPC_NOMOD)
 
=== modified file 'src/rec/calcRecord.c'
--- src/rec/calcRecord.c	2009-04-03 14:40:13 +0000
+++ src/rec/calcRecord.c	2010-05-28 09:22:29 +0000
@@ -37,6 +37,9 @@
 #undef  GEN_SIZE_OFFSET
 #include "epicsExport.h"
 
+/* Hysterisis for alarm filtering: 1-1/e */
+#define THRESHOLD 0.6321
+
 /* Create RSET - Record Support Entry Table */
 
 #define report NULL
@@ -79,7 +82,7 @@
 };
 epicsExportAddress(rset, calcRSET);
 
-static void checkAlarms(calcRecord *prec);
+static void checkAlarms(calcRecord *prec, epicsTimeStamp *timeLast);
 static void monitor(calcRecord *prec);
 static int fetch_values(calcRecord *prec);
 
@@ -111,15 +114,19 @@
 
 static long process(calcRecord *prec)
 {
+    epicsTimeStamp timeLast;
+
     prec->pact = TRUE;
     if (fetch_values(prec)==0) {
 	if (calcPerform(&prec->a, &prec->val, prec->rpcl)) {
 	    recGblSetSevr(prec, CALC_ALARM, INVALID_ALARM);
 	} else prec->udf = isnan(prec->val);
     }
+
+    timeLast = prec->time;
     recGblGetTimeStamp(prec);
     /* check for alarms */
-    checkAlarms(prec);
+    checkAlarms(prec, &timeLast);
     /* check event list */
     monitor(prec);
     /* process the forward scan link record */
@@ -243,14 +250,27 @@
     return 0;
 }
 
-static void checkAlarms(calcRecord *prec)
+static void checkAlarms(calcRecord *prec, epicsTimeStamp *timeLast)
 {
-    double val, hyst, lalm;
-    double alev;
+
+	enum {
+		range_Lolo = 1,
+		range_Low,
+		range_Normal,
+		range_High,
+		range_Hihi
+	} alarmRange;
+	static const epicsEnum16 range_stat[] = {
+		SOFT_ALARM, LOLO_ALARM, LOW_ALARM, 
+		NO_ALARM, HIGH_ALARM, HIHI_ALARM
+	};
+
+    double val, hyst, lalm, alev, aftc, afvl;
     epicsEnum16 asev;
 
     if (prec->udf) {
         recGblSetSevr(prec, UDF_ALARM, INVALID_ALARM);
+	prec->afvl = 0;
         return;
     }
 
@@ -258,45 +278,89 @@
     hyst = prec->hyst;
     lalm = prec->lalm;
 
-    /* alarm condition hihi */
-    asev = prec->hhsv;
-    alev = prec->hihi;
-    if (asev && (val >= alev || ((lalm == alev) && (val >= alev - hyst)))) {
-        if (recGblSetSevr(prec, HIHI_ALARM, asev))
-            prec->lalm = alev;
-        return;
-    }
-
-    /* alarm condition lolo */
-    asev = prec->llsv;
-    alev = prec->lolo;
-    if (asev && (val <= alev || ((lalm == alev) && (val <= alev + hyst)))) {
-        if (recGblSetSevr(prec, LOLO_ALARM, asev))
-            prec->lalm = alev;
-        return;
-    }
-
-    /* alarm condition high */
-    asev = prec->hsv;
-    alev = prec->high;
-    if (asev && (val >= alev || ((lalm == alev) && (val >= alev - hyst)))) {
-        if (recGblSetSevr(prec, HIGH_ALARM, asev))
-            prec->lalm = alev;
-        return;
-    }
-
-    /* alarm condition low */
-    asev = prec->lsv;
-    alev = prec->low;
-    if (asev && (val <= alev || ((lalm == alev) && (val <= alev + hyst)))) {
-        if (recGblSetSevr(prec, LOW_ALARM, asev))
-            prec->lalm = alev;
-        return;
-    }
-
-    /* we get here only if val is out of alarm by at least hyst */
-    prec->lalm = val;
-    return;
+        /* check VAL against alarm limits */
+    if ((asev = prec->hhsv) &&
+        (val >= (alev = prec->hihi) ||
+         ((lalm == alev) && (val >= alev - hyst))))
+        alarmRange = range_Hihi;
+    else
+    if ((asev = prec->llsv) &&
+        (val <= (alev = prec->lolo) ||
+         ((lalm == alev) && (val <= alev + hyst))))
+        alarmRange = range_Lolo;
+    else
+    if ((asev = prec->hsv) &&
+        (val >= (alev = prec->high) ||
+         ((lalm == alev) && (val >= alev - hyst))))
+        alarmRange = range_High;
+    else
+    if ((asev = prec->lsv) &&
+        (val <= (alev = prec->low) ||
+         ((lalm == alev) && (val <= alev + hyst))))
+        alarmRange = range_Low;
+    else {
+        alev = val;
+        asev = NO_ALARM;
+        alarmRange = range_Normal;
+    }
+
+    aftc = prec->aftc;
+    afvl = 0;
+
+    if (aftc > 0) {
+        /* Apply level filtering */
+        afvl = prec->afvl;
+        if (afvl == 0) {
+            afvl = (double)alarmRange;
+        } else {
+            double t = epicsTimeDiffInSeconds(&prec->time, timeLast);
+            double alpha = aftc / (t + aftc);
+
+            /* The sign of afvl indicates whether the result should be
+             * rounded up or down.  This gives the filter hysteresis.
+             * If afvl > 0 the floor() function rounds to a lower alarm
+             * level, otherwise to a higher.
+             */
+            afvl = alpha * afvl +
+                   ((afvl > 0) ? (1 - alpha) : (alpha - 1)) * alarmRange;
+            if (afvl - floor(afvl) > THRESHOLD)
+                afvl = -afvl; /* reverse rounding */
+
+            alarmRange = abs((int)floor(afvl));
+            switch (alarmRange) {
+            case range_Hihi:
+                asev = prec->hhsv;
+                alev = prec->hihi;
+                break;
+            case range_High:
+                asev = prec->hsv;
+                alev = prec->high;
+                break;
+            case range_Normal:
+                asev = NO_ALARM;
+                break;
+            case range_Low:
+                asev = prec->lsv;
+                alev = prec->low;
+                break;
+            case range_Lolo:
+                asev = prec->llsv;
+                alev = prec->lolo;
+                break;
+            }
+        }
+    }
+    prec->afvl = afvl;
+
+    if (asev) {
+        /* Report alarm condition, store LALM for future HYST calculations */
+        if (recGblSetSevr(prec, range_stat[alarmRange], asev))
+            prec->lalm = alev;
+    } else {
+        /* No alarm condition, reset LALM */
+        prec->lalm = val;
+    }
+
 }
 
 static void monitor(calcRecord *prec)
 
=== modified file 'src/rec/calcRecord.dbd'
--- src/rec/calcRecord.dbd	2007-03-13 16:39:53 +0000
+++ src/rec/calcRecord.dbd	2010-05-28 09:22:29 +0000
@@ -153,6 +153,16 @@
 		interest(1)
 		menu(menuAlarmSevr)
 	}
+        field(AFTC, DBF_DOUBLE) {
+                prompt("Alarm Filter Time Constant")
+                promptgroup(GUI_ALARMS)
+                interest(1)
+        }
+        field(AFVL, DBF_DOUBLE) {
+                prompt("Alarm Filter Value")
+                special(SPC_NOMOD)
+                interest(3)
+        }
 	field(HYST,DBF_DOUBLE) {
 		prompt("Alarm Deadband")
 		promptgroup(GUI_ALARMS)
 
=== modified file 'src/rec/longinRecord.c'
--- src/rec/longinRecord.c	2010-04-05 18:49:18 +0000
+++ src/rec/longinRecord.c	2010-05-28 09:22:29 +0000
@@ -37,6 +37,8 @@
 #undef  GEN_SIZE_OFFSET
 #include "epicsExport.h"
 
 
+
 /* Hysterisis for alarm filtering: 1-1/e */
+#define THRESHOLD 0.6321
 /* Create RSET - Record Support Entry Table*/
 #define report NULL
 #define initialize NULL
@@ -87,7 +89,7 @@
 	DEVSUPFUN	get_ioint_info;
 	DEVSUPFUN	read_longin; /*returns: (-1,0)=>(failure,success)*/
 };
-static void checkAlarms(longinRecord *prec);
+static void checkAlarms(longinRecord *prec, epicsTimeStamp *timeLast);
 static void monitor(longinRecord *prec);
 static long readValue(longinRecord *prec);
 
@@ -132,12 +134,14 @@
 	struct longindset	*pdset = (struct longindset *)(prec->dset);
 	long		 status;
 	unsigned char    pact=prec->pact;
+	epicsTimeStamp   timeLast;
 
 	if( (pdset==NULL) || (pdset->read_longin==NULL) ) {
 		prec->pact=TRUE;
 		recGblRecordError(S_dev_missingSup,(void *)prec,"read_longin");
 		return(S_dev_missingSup);
 	}
+	timeLast = prec->time;
 
 	status=readValue(prec); /* read the new value */
 	/* check if device support set pact */
@@ -148,7 +152,7 @@
 	if (status==0) prec->udf = FALSE;
 
 	/* check for alarms */
-	checkAlarms(prec);
+	checkAlarms(prec, &timeLast);
 	/* check event list */
 	monitor(prec);
 	/* process the forward scan link record */
@@ -210,14 +214,28 @@
     return(0);
 }
 
 
-static void checkAlarms(longinRecord *prec)
+static void checkAlarms(longinRecord *prec, epicsTimeStamp *timeLast)
 {
+	enum {
+        range_Lolo = 1,
+        range_Low,
+        range_Normal,
+        range_High,
+        range_Hihi
+    } alarmRange;
+    static const epicsEnum16 range_stat[] = {
+        SOFT_ALARM, LOLO_ALARM, LOW_ALARM,
+        NO_ALARM, HIGH_ALARM, HIHI_ALARM
+    };
+    
+    double aftc, afvl;
     epicsInt32 val, hyst, lalm;
     epicsInt32 alev;
     epicsEnum16 asev;
 
     if (prec->udf) {
         recGblSetSevr(prec, UDF_ALARM, INVALID_ALARM);
+        prec->afvl = 0;
         return;
     }
 
@@ -225,45 +243,88 @@
     hyst = prec->hyst;
     lalm = prec->lalm;
 
-    /* alarm condition hihi */
-    asev = prec->hhsv;
-    alev = prec->hihi;
-    if (asev && (val >= alev || ((lalm == alev) && (val >= alev - hyst)))) {
-        if (recGblSetSevr(prec, HIHI_ALARM, asev))
-            prec->lalm = alev;
-        return;
-    }
-
-    /* alarm condition lolo */
-    asev = prec->llsv;
-    alev = prec->lolo;
-    if (asev && (val <= alev || ((lalm == alev) && (val <= alev + hyst)))) {
-        if (recGblSetSevr(prec, LOLO_ALARM, asev))
-            prec->lalm = alev;
-        return;
-    }
-
-    /* alarm condition high */
-    asev = prec->hsv;
-    alev = prec->high;
-    if (asev && (val >= alev || ((lalm == alev) && (val >= alev - hyst)))) {
-        if (recGblSetSevr(prec, HIGH_ALARM, asev))
-            prec->lalm = alev;
-        return;
-    }
-
-    /* alarm condition low */
-    asev = prec->lsv;
-    alev = prec->low;
-    if (asev && (val <= alev || ((lalm == alev) && (val <= alev + hyst)))) {
-        if (recGblSetSevr(prec, LOW_ALARM, asev))
-            prec->lalm = alev;
-        return;
-    }
-
-    /* we get here only if val is out of alarm by at least hyst */
-    prec->lalm = val;
-    return;
+    /* check VAL against alarm limits */
+    if ((asev = prec->hhsv) &&
+        (val >= (alev = prec->hihi) ||
+         ((lalm == alev) && (val >= alev - hyst))))
+        alarmRange = range_Hihi;
+    else
+    if ((asev = prec->llsv) &&
+        (val <= (alev = prec->lolo) ||
+         ((lalm == alev) && (val <= alev + hyst))))
+        alarmRange = range_Lolo;
+    else
+    if ((asev = prec->hsv) &&
+        (val >= (alev = prec->high) ||
+         ((lalm == alev) && (val >= alev - hyst))))
+        alarmRange = range_High;
+    else
+    if ((asev = prec->lsv) &&
+        (val <= (alev = prec->low) ||
+         ((lalm == alev) && (val <= alev + hyst))))
+        alarmRange = range_Low;
+    else {
+        alev = val;
+        asev = NO_ALARM;
+        alarmRange = range_Normal;
+    }
+
+    aftc = prec->aftc;
+    afvl = 0;
+
+    if (aftc > 0) {
+        /* Apply level filtering */
+        afvl = prec->afvl;
+        if (afvl == 0) {
+            afvl = (double)alarmRange;
+        } else {
+            double t = epicsTimeDiffInSeconds(&prec->time, timeLast);
+            double alpha = aftc / (t + aftc);
+
+            /* The sign of afvl indicates whether the result should be
+             * rounded up or down.  This gives the filter hysteresis.
+             * If afvl > 0 the floor() function rounds to a lower alarm
+             * level, otherwise to a higher.
+             */
+            afvl = alpha * afvl +
+                   ((afvl > 0) ? (1 - alpha) : (alpha - 1)) * alarmRange;
+            if (afvl - floor(afvl) > THRESHOLD)
+                afvl = -afvl; /* reverse rounding */
+
+            alarmRange = abs((int)floor(afvl));
+            switch (alarmRange) {
+            case range_Hihi:
+                asev = prec->hhsv;
+                alev = prec->hihi;
+                break;
+            case range_High:
+                asev = prec->hsv;
+                alev = prec->high;
+                break;
+            case range_Normal:
+                asev = NO_ALARM;
+                break;
+            case range_Low:
+                asev = prec->lsv;
+                alev = prec->low;
+                break;
+            case range_Lolo:
+                asev = prec->llsv;
+                alev = prec->lolo;
+                break;
+            }
+        }
+    }
+    prec->afvl = afvl;
+
+    if (asev) {
+        /* Report alarm condition, store LALM for future HYST calculations */
+        if (recGblSetSevr(prec, range_stat[alarmRange], asev))
+            prec->lalm = alev;
+    } else {
+        /* No alarm condition, reset LALM */
+        prec->lalm = val;
+    }
 }
 
 
 /* DELTA calculates the absolute difference between its arguments
 
=== modified file 'src/rec/longinRecord.dbd'
--- src/rec/longinRecord.dbd	2002-07-12 21:35:43 +0000
+++ src/rec/longinRecord.dbd	2010-05-28 09:22:29 +0000
@@ -93,6 +93,16 @@
 		promptgroup(GUI_ALARMS)
 		interest(1)
 	}
+        field(AFTC, DBF_DOUBLE) {
+                prompt("Alarm Filter Time Constant")
+                promptgroup(GUI_ALARMS)
+                interest(1)
+        }
+        field(AFVL, DBF_DOUBLE) {
+                prompt("Alarm Filter Value")
+                special(SPC_NOMOD)
+                interest(3)
+        }
 	field(ADEL,DBF_LONG) {
 		prompt("Archive Deadband")
 		promptgroup(GUI_DISPLAY)
 
=== modified file 'src/rec/mbbiRecord.c'
--- src/rec/mbbiRecord.c	2010-04-05 18:49:18 +0000
+++ src/rec/mbbiRecord.c	2010-05-28 09:22:29 +0000
@@ -36,6 +36,9 @@
 #include "mbbiRecord.h"
 #undef  GEN_SIZE_OFFSET
 #include "epicsExport.h"
+
+/* Hysterisis for alarm filtering: 1-1/e */
+#define THRESHOLD 0.6321
 /* Create RSET - Record Support Entry Table*/
 #define report NULL
 #define initialize NULL
@@ -84,7 +87,7 @@
 	DEVSUPFUN	get_ioint_info;
 	DEVSUPFUN	read_mbbi;/*(0,2)=>(success, success no convert)*/
 };
-static void checkAlarms(mbbiRecord *);
+static void checkAlarms(mbbiRecord *, epicsTimeStamp *);
 static void monitor(mbbiRecord *);
 static long readValue(mbbiRecord *);
 
 
@@ -146,6 +149,7 @@
 	struct mbbidset	*pdset = (struct mbbidset *)(prec->dset);
 	long		status;
 	unsigned char    pact=prec->pact;
+	epicsTimeStamp   timeLast;
 
 	if( (pdset==NULL) || (pdset->read_mbbi==NULL) ) {
 		prec->pact=TRUE;
@@ -153,6 +157,8 @@
 		return(S_dev_missingSup);
 	}
 
+	timeLast = prec->time;
+
 	status=readValue(prec); /* read the new value */
 	/* check if device support set pact */
 	if ( !pact && prec->pact ) return(0);
@@ -184,7 +190,7 @@
 	else if(status == 2) status = 0;
 
 	/* check for alarms */
-	checkAlarms(prec);
+	checkAlarms(prec, &timeLast);
 
 	/* check event list */
 	monitor(prec);
@@ -274,14 +280,20 @@
 	return(S_db_badChoice);
 }
 
-static void checkAlarms(mbbiRecord *prec)
+static void checkAlarms(mbbiRecord *prec, epicsTimeStamp *timeLast)
 {
+	
+    double aftc, afvl;
+   
+        unsigned short alarm; 
+	epicsEnum16 asev;
 	unsigned short *severities;
 	unsigned short	val=prec->val;
 
         /* check for udf alarm */
         if(prec->udf == TRUE ){
                 recGblSetSevr(prec,UDF_ALARM,INVALID_ALARM);
+                prec->afvl = 0;
         }
 
         /* check for  state alarm */
@@ -291,8 +303,36 @@
         } else {
         	/* in a state which is an error */
         	severities = (unsigned short *)&(prec->zrsv);
+		/*
                 recGblSetSevr(prec,STATE_ALARM,severities[prec->val]);
-	}
+		*/
+		alarm = severities[prec->val];
+
+	}
+
+	aftc = prec->aftc;
+	afvl = 0.;
+
+	if(aftc > 0.) {
+		afvl = prec->afvl;
+		if(afvl == 0.) {
+			afvl = (double) alarm;
+		} else {
+			double t = epicsTimeDiffInSeconds(&prec->time, timeLast);
+			double alpha = aftc / (t + aftc);
+
+			afvl = alpha * afvl +
+				((afvl>0.)?(1.-alpha):(alpha-1.)) * alarm;
+			if(afvl - floor(afvl) > THRESHOLD)
+				afvl = -afvl;
+
+			alarm = abs((int)floor(afvl));
+		}
+	}
+
+
+	asev = alarm;
+	recGblSetSevr(prec, STATE_ALARM, asev);
 
         /* check for cos alarm */
 	if(val == prec->lalm) return;
 
=== modified file 'src/rec/mbbiRecord.dbd'
--- src/rec/mbbiRecord.dbd	2009-06-08 19:55:49 +0000
+++ src/rec/mbbiRecord.dbd	2010-05-28 09:22:29 +0000
@@ -394,6 +394,16 @@
 		interest(1)
 		menu(menuAlarmSevr)
 	}
+        field(AFTC, DBF_DOUBLE) {
+                prompt("Alarm Filter Time Constant")
+                promptgroup(GUI_ALARMS)
+                interest(1)
+        }
+        field(AFVL, DBF_DOUBLE) {
+                prompt("Alarm Filter Value")
+                special(SPC_NOMOD)
+                interest(3)
+        }
 	field(UNSV,DBF_MENU) {
 		prompt("Unknown State Severity")
 		promptgroup(GUI_MBB)