RRM 3-14 Long Output

EPICS Record Reference Manual

longout - Long Output

The normal use for the long output or "longout" record type is to store long integer values of up to 32 bits and write them to hardware devices. The Soft Channel device support routine can also be used to write values to other records via database or channel access links. The OUT field determines how the record is used. The record supports alarm limits and graphics and control limits.

Parameter Fields

The fields in this record fall into the following categories:

• scan parameters
• desired output parameters
• write parameters
• operator display parameters
• alarm parameters
• monitor parameters
• simulation mode parameters

Scan Parameters

The longout record has the standard fields for specifying under what circumstances it will be processed. These fields are listed in Scan Fields. In addition, Scanning Specification explains how these fields are used. Note that I/O event scanning is only supported for those card types that interrupt.

Desired Output Parameters

The record must specify where the desired output originates, i.e., the 32 bit integer value it is to write. The output mode select (OMSL) field determines whether the output originates from another record or from database access. When set to closed_loop, the desired output is retrieved from the link specified in the desired output (DOL) field--which can specify either a database or channel access link--and placed into the VAL field. When set to supervisory, the desired output can be written into the VAL field via dpPuts at run-time.

A third type of value for the DOL field is a constant in which case, when the record is initialized, the VAL field will be initialized with this constant value.

The VAL field's value will be clipped within limits specified in the fields DRVH and DRVL if these have been configured by the database designer:

DRVL <= VAL <= DRVH

Note: These limits are only enforced as long as DRVH > DRVL. If they are not set or DRVH <= DRVL they will not be used.

Field	Summary	Type	DCT	Initial	Access	Modify	Rec Proc Monitor	PP
DOL	Desired Output Location (input link)	INLINK	Yes	0	Yes	Yes	No	No
OMSL	Output Mode Select	GBLCHOICE	Yes	0	Yes	Yes	No	No
DRVH	Drive High	LONG	Yes	0	Yes	Yes	No	Yes
DRVL	Drive Low	LONG	Yes	0	Yes	Yes	No	Yes
VAL	Value Field	LONG	No	0	Yes	Yes	Yes	Yes

Write Parameters

The OUT link field determines where the record is to send its output. For records that write values to hardware devices, the OUT output link field must specify the address of the I/O card, and the DTYP field must specify the name of the corresponding device support module. You can see a list of the device support modules currently supported at the user's local site by using the dbst utility in R3.13.

For soft records, the OUT output link can be a constant, a database link, or a channel access link. If the link is a constant, the result is no output. The DTYP field must then specify the Soft Channel device support routine.

See Address Specification for information on the format of hardware addresses and database links.

Field	Summary	Type	DCT	Initial	Access	Modify	Rec Proc Monitor
OUT	Output Link	OUTLINK	Yes	0	Yes	Yes	No
DTYP	Device Type	DEVCHOICE	Yes	0	Yes	No	No

Operator Display Parameters

These parameters are used to present meaningful data to the operator. They display the value and other parameters of the long output either textually or graphically.

EGU is a string of up to 16 characters describing the units that the long output measures. It is retrieved by the get_units record support routine.

The HOPR and LOPR fields set the upper and lower display limits for the VAL, HIHI, HIGH, LOW, and LOLO fields. Both the get_graphic_double and get_control_double record support routines retrieve these fields.

See Fields Common to All Record Types for more on the record name (NAME) and description (DESC) fields.

Field	Summary	Type	DCT	Initial	Access	Modify	Rec Proc Monitor	PP
EGU	Engineering Units	STRING [16]	Yes	null	Yes	Yes	No	No
HOPR	High Operating Range	FLOAT	Yes	0	Yes	Yes	No	No
LOPR	Low Operating Range	FLOAT	Yes	0	Yes	Yes	No	No
NAME	Record Name	STRING [29]	Yes	0	Yes	No	No
DESC	Description	STRING [29]	Yes	Null	Yes	Yes	No	No

Alarm Parameters

The possible alarm conditions for long inputs are the SCAN, READ, INVALID, and limit alarms. The SCAN and READ alarms are not configurable by the user because their severity is always MAJOR. The INVALID alarm is called by the record support routine when the record or device support routines cannot write the record's output. The IVOA field specifies the action to take in this case.

The limit alarms are configured by the user in the HIHI, LOLO, HIGH, and LOW fields using floating-point values. For each of these fields, there is a corresponding severity field which can be either NO_ALARM, MINOR, or MAJOR. The HYST field contains the alarm deadband around each limit alarm.

See the See Alarm Specification for a complete explanation of alarms and these fields. For an explanation of the IVOA and IVOV fields, see Output Records. Alarm Fields lists other fields related to a alarms that are common to all record types.

Field	Summary	Type	DCT	Initial	Access	Modify	Rec Proc Monitor	PP
HIHI	Hihi Alarm Limit	FLOAT	Yes	0	Yes	Yes	No	Yes
HIGH	High Alarm Limit	FLOAT	Yes	0	Yes	Yes	No	Yes
LOW	Low Alarm Limit	FLOAT	Yes	0	Yes	Yes	No	Yes
LOLO	Lolo Alarm Limit	FLOAT	Yes	0	Yes	Yes	No	Yes
HHSV	Hihi Alarm Severity	GBLCHOICE	Yes	0	Yes	Yes	No	Yes
HSV	High Alarm Severity	GBLCHOICE	Yes	0	Yes	Yes	No	Yes
LSV	Low Alarm Severity	GBLCHOICE	Yes	0	Yes	Yes	No	Yes
LLSV	Lolo Alarm Severity	GBLCHOICE	Yes	0	Yes	Yes	No	Yes
HYST	Alarm Deadband	DOUBLE	Yes	0	Yes	Yes	No	No
IVOA	Invalid Alarm Output Action	GBLCHOICE	Yes	0	Yes	Yes	No	No
IVOV	Invalid Alarm Output Value, in eng. units	DOUBLE	Yes	0	Yes	Yes	No	No

Monitor Parameters

These parameters are used to determine when to send monitors placed on the value field. The monitors are sent when the value field exceeds the last monitored field by the appropriate delta. If these fields have a value of zero, everytime the value changes, a monitor will be triggered; if they have a value of -1, everytime the record is scanned, monitors are triggered. The ADEL field is the delta for archive monitors, and the MDEL field is the delta for all other types of monitors. See Monitor Specification for a complete explanation of monitors.

Field	Summary	Type	DCT	Initial	Access	Modify	Rec Proc Monitor	PP
ADEL	Archive Deadband	DOUBLE	Yes	0	Yes	Yes	No	No
MDEL	Monitor, i.e. value change, Deadband	DOUBLE	Yes	0	Yes	Yes	No	No

Run-time and Simulation Mode Parameters

The LALM, MLST, and ALST fields are used to implement the hysteresis factors for monitor callbacks. Only if the difference between these fields and the corresponding value field is greater than the appropriate delta (MDEL, ADEL, HYST)--only then are monitors triggered. For instance, only if the difference between VAL and MLST is greater than MDEL are the monitors triggered for VAL.

Field	Summary	Type	DCT	Initial	Access	Modify	Rec Proc Monitor	PP
LALM	Last Alarm Monitor Trigger Value	DOUBLE	No	0	Yes	No	No	No
ALST	Last Archiver Monitor Trigger Value	DOUBLE	No	0	Yes	No	No	No
MLST	Last Value Change Monitor Trigger Value	DOUBLE	No	0	Yes	No	No	No

The following fields are used to operate the long output in the simulation mode. See Fields Common to Many Record Types for more information on the simulation mode fields

Field	Summary	Type	DCT	Initial	Access	Modify	Rec Proc Monitor	PP
SIOL	Simulation Value Location	INLINK	Yes	0	Yes	Yes	No	No
SIML	Simulation Mode Location	INLINK	Yes	0	Yes	Yes	No	No
SIMM	Simulation Mode	GBLCHOICE	No	0	Yes	Yes	No	No
SIMS	Simulation Mode Alarm Severity	GBLCHOICE	Yes	0	Yes	Yes	No	No

Record Support

Record Support Routines

init_record

This routine initializes SIMM if SIML is a constant or creates a channel access link if SIML is PV_LINK. If SIOL is PV_LINK a channel access link is created.

This routine next checks to see that device support is available. The routine next checks to see if the device support write routine is defined.

If either device support or the device support write routine does not exist, an error message is issued and processing is terminated.

If DOL is a constant, then VAL is initialized to its value and UDF is set to FALSE. If DOL type is a PV_LINK then dbCaAddInlink is called to create a channel access link.

If device support includes init_record, it is called.

process

See next section.

get_value

Fills in the values of struct valueDes so that they refer to VAL.

get_units

Retrieves EGU.

get_graphic_double

Sets the upper display and lower display limits for a field. If the field is VAL, HIHI, HIGH, LOW, or LOLO, the limits are set to HOPR and LOPR, else if the field has upper and lower limits defined they will be used, else the upper and lower maximum values for the field type will be used.

get_control_double

Sets the upper control and the lower control limits for a field. If the field is VAL, HIHI, HIGH, LOW, or LOLO, the limits are set to HOPR and LOPR, else if the field has upper and lower limits defined they will be used, else the upper and lower maximum values for the field type will be used.

get_alarm_double

Sets the following values:

 upper_alarm_limit = HIHI
 upper_warning_limit = HIGH
 lower_warning_limit = LOW
 lower_alarm_limit = LOLO

Record Processing

Routine process implements the following algorithm:

1. Check to see that the appropriate device support module exists. If it doesn't, an error message is issued and processing is terminated with the PACT field still set to TRUE. This ensures that processes will no longer be called for this record. Thus error storms will not occur.
2. If PACT is FALSE and OMSL is CLOSED_LOOP recGblGetLinkValue is called to read the current value of VAL. See Output Records for more information. If the return status of recGblGetLinkValue is zero then UDF is set to FALSE.
3. Check alarms. This routine checks to see if the new VAL causes the alarm status and severity to change. If so, NSEV, NSTA and LALM are set. It also honors the alarm hysteresis factor (HYST). Thus the value must change by more than HYST before the alarm status and severity is lowered.
4. Check severity and write the new value. See Invalid Alarm Output Action for information on how INVALID alarms affect output records.
5. If PACT has been changed to TRUE, the device support write output routine has started but has not completed writing the new value. In this case, the processing routine merely returns, leaving PACT TRUE.
6. Check to see if monitors should be invoked:
   • Alarm monitors are invoked if the alarm status or severity has changed.
   • Archive and value change monitors are invoked if ADEL and MDEL conditions are met.
   • NSEV and NSTA are reset to 0.
7. Scan forward link if necessary, set PACT FALSE, and return.

Device Support

Fields Of Interest To Device Support

Each long output record must have an associated set of device support routines. The primary responsibility of the device support routines is to output a new value whenever write_longout is called. The device support routines are primarily interested in the following fields:

Name	Summary	Description
PACT	Processing Active	See Fields Common to All Record Types for an explanation of these fields.
DPVT	Device Private
NSEV	New Alarm Severity
NSTA	New Alarm Status
OUT	Output Link	This field is used by the device support routines to locate its output.

Device Support Routines

Device support consists of the following routines:

init

init()

This routine is called once during IOC initialization.

init_record

init_record(precord)

This routine is optional. If provided, it is called by the record support init_record routine.

get_ioint_info

get_ioint_info(int cmd,struct dbCommon *precord,IOSCANPVT *ppvt)

This routine is called by the ioEventScan system each time the record is added or deleted from an I/O event scan list. cmd has the value (0,1) if the record is being (added to, deleted from) an I/O event list. It must be provided for any device type that can use the ioEvent scanner.

write_longout

write_longout(precord)

This routine must output a new value. It returns the following values:

• 0: Success.
• Other: Error.

Device Support For Soft Records

The Soft Channel module writes the current value of VAL.

If the OUT link type is PV_LINK, then dbCaAddInlink is called by init_record.

write_longout calls recGblPutLinkValue to write the current value of VAL.

See Soft Output for a further explanation.

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EPICS Record Reference Manual - 19 MAY 1998