NB: This manual refers to a very old version of EPICS, see the EPICS Wiki for updated record reference documentation.

[Next] [Previous] [Top] [Contents] [Index]

EPICS Record Reference Manual

Chapter 18: longout - Long Output

1. Introduction


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.

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

2. 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, Chapter 2, 2. In addition, Scanning Specification, Chapter 1, 1, explains how these fields are used. Note that I/O event scanning is only supported for those card types that interrupt.

3. Desired Output Parameters


The data fanout 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.

The DOL field can be configured as constant, so that when the record is initialized, the VAL field will be initialized with this VALUE. If DOL is a constant, then the OMSL loop cannot be closed_loop.
FieldSummaryTypeDCTInitialAccessModifyRec Proc Monitor
DOLDesired Output Location (input link)INLINKYes0NoNoN/A
OMSLOutput Mode SelectGBLCHOICEYes0YesYesNo
VALValue FieldLONGNo0YesYesYes

4. 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, Chapter 1, 2, for information on the format of hardware addresses and database links.
FieldSummaryTypeDCTInitialAccessModifyRec Proc Monitor
OUTOutput LinkOUTLINKYes0NoNoN/A
DTYPDevice TypeDEVCHOICEYes0YesNoNo

5. 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 Chapter 2, Fields Common to All Record Types, for more on the record name (NAME) and description (DESC) fields.
FieldSummaryTypeDCTInitialAccessModifyRec Proc MonitorPP
EGUEngineering UnitsSTRING [16]YesnullYesYesNoNo
HOPRHigh Operating RangeFLOATYes0YesYesNoNo
LOPRLow Operating RangeFLOATYes0YesYesNoNo
NAMERecord NameSTRING [29]Yes0YesNoNo 
DESCDescriptionSTRING [29]YesNullYesYesNoNo

6. 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, Chapter 1, 4, for a complete explanation of alarms and these fields. For an explanation of the IVOA and IVOV fields, see Output Records, Chapter 3, 3. Alarm Fields, Chapter 2, 3, lists other fields related to a alarms that are common to all record types.
FieldSummaryTypeDCTInitialAccessModifyRec Proc MonitorPP
HIHIHihi Alarm LimitFLOATYes0YesYesNoYes
HIGHHigh Alarm LimitFLOATYes0YesYesNoYes
LOWLow Alarm LimitFLOATYes0YesYesNoYes
LOLOLolo Alarm LimitFLOATYes0YesYesNoYes
HHSVHihi Alarm SeverityGBLCHOICEYes0YesYesNoYes
HSVHigh Alarm SeverityGBLCHOICEYes0YesYesNoYes
LSVLow Alarm SeverityGBLCHOICEYes0YesYesNoYes
LLSVLolo Alarm SeverityGBLCHOICEYes0YesYesNoYes
HYSTAlarm DeadbandDOUBLEYes0YesYesNoNo
IVOAInvalid Alarm Output ActionGBLCHOICEYes0YesYesNoNo
IVOVInvalid Alarm Output Value, in eng. unitsDOUBLEYes0YesYesNoNo

7. 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, Chapter 1, 5, for a complete explanation of monitors.
FieldSummaryTypeDCTInitialAccessModifyRec Proc MonitorPP
ADELArchive DeadbandDOUBLEYes0YesYesNoNo
MDELMonitor, i.e. value change, DeadbandDOUBLEYes0YesYesNoNo

8. 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.
FieldSummaryTypeDCTInitialAccessModifyRec Proc MonitorPP
LALMLast Alarm Monitor Trigger ValueDOUBLENo0YesNoNoNo
ALSTLast Archiver Monitor Trigger ValueDOUBLENo0YesNoNoNo
MLSTLast Value Change Monitor Trigger ValueDOUBLENo0YesNoNoNo

The following fields are used to operate the long output in the simulation mode. See Chapter 3, Fields Common to Many Record Types, for more information on the simulation mode fields
FieldSummaryTypeDCTInitialAccessModifyRec Proc MonitorPP
SIOLSimulation Value LocationINLINKYes0NoNoN/ANo
SVALSimulation ValueDOUBLENo0YesYesNoNo
SIMLSimulation Mode LocationINLINKYes0NoNoN/ANo
SIMMSimulation ModeGBLCHOICENo0YesYesNoNo
SIMSSimulation Mode Alarm SeverityGBLCHOICEYes0YesYesNoNo

9. 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

10. 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, Chapter 3, 3, 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, Chapter 3, 3.5, 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.

7. Scan forward link if necessary, set PACT FALSE, and return.

11. Device Support


11.1. 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:


NameSummaryDescription
PACTProcessing ActiveSee Chapter 2, Fields Common to All Record Types for an explanation of these fields.
DPVTDevice Private
NSEVNew Alarm Severity
NSTANew Alarm Status
OUTOutput LinkThis field is used by the device support routines to locate its output.

11.2. 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:

11.3. 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, Chapter 3, 3.2, for a further explanation.

1. - Introduction
2. - Scan Parameters
3. - Desired Output Parameters
4. - Write Parameters
5. - Operator Display Parameters
6. - Alarm Parameters
7. - Monitor Parameters
8. - Run-time and Simulation Mode Parameters
9. - Record Support Routines
init_record
process
get_value
get_units
get_graphic_double
get_control_double
get_alarm_double
10. - Record Processing
11. - Device Support
11.1. - Fields Of Interest To Device Support
11.2. - Device Support Routines
init
init_record
get_ioint_info
write_longout
11.3. - Device Support For Soft Records

EPICS Record Reference Manual - 19 MAY 1998
[Next] [Previous] [Top] [Contents] [Index]

Generated with Harlequin WebMaker