RRM 3-14 String Output

EPICS Record Reference Manual

stringout -- String Output

The stringout record is used to write an arbitrary ASCII string of up to 40 characters to other records or software variables.

Parameter Fields

The fields fall into the following categories:

• scan parameters
• desired output parameters
• write parameters
• operator display parameters
• run-time parameters

Scan Parameters

The string output 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.

Desired Output Parameters

The string output record must specify from where it gets its desired output string. The first field that determines where the desired output originates is the output mode select (OSML) field, which can have two possible value: closed_loop or supervisory. If supervisory is specified, DOL is ignored, the current value of VAL is written, and the VAL can be changed externally via dbPuts at run-time. If closed_loop is specified, the VAL field's value is obtained from the address specified in the desired output location field (DOL) which can be either a database link or a channel access link.

DOL can also be a constant in addition to a link, in which case VAL is initialized to the constant value. Note that if DOL is a constant, OMSL cannot be closed_loop. See Address Specification for information on specifying links.

Field	Summary	Type	DCT	Initial	Access	Modify	Rec Proc Monitor	PP
VAL	Value Field	STRING [40]	Yes	Null	Yes	Yes	Yes	Yes
DOL	Desired Output Location (Input Link)	INLINK	Yes	0	No	No	N/A	No
OMSL	Output Mode Select	GBLCHOICE	Yes	0	Yes	Yes	No	No

Write Parameters

The output link specified in the OUT field specifies where the string output record is to write its string. The link can be a database or channel access link. If the OUT field is a constant, no output will be written. See Address Specification for information on specifying links.

In addition, the appropriate device support module must be entered into the DTYP field. All string output records must specify a device support module. The user can see a list of the device support modules currently supported at the user's local site by using the dbst utility (R3.13).

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

Operator Display Parameters

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

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
NAME	Record Name	STRING [29]	Yes	0	Yes	No	No	No
DESC	Description	STRING [29]	Yes	Null	Yes	Yes	No	No

Alarm Parameters

The possible alarm conditions for the string output record are the SCAN, READ, and INVALID alarms. The severity of the first two is always MAJOR and not configurable.

The IVOA field specifies an action to take when the INVALID alarm is triggered. There are three possible actions: Continue normally, Don't drive outputs, and Set output to IVOV. When Set output to IVOV, the value contained in the IVOV field is written to the output link during an alarm condition. See Invalid Alarm Output Action for more information on the IVOA and IVOV fields. 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
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

Run-time and Simulation Mode Parameters

The old value field (OVAL) of the string input is used to implement value change monitors for VAL. If VAL is not equal to OVAL, then monitors are triggered.

Field	Summary	Type	DCT	Initial	Access	Modify	Rec Proc Monitor	PP
OVAL	Output Value	STRING [40]	No	Null	Yes	No	No	No

The following fields are used to operate the string output in the simulation mode. See Simulation Mode for more information on these fields.

Field	Summary	Type	DCT	Initial	Access	Modify	Rec Proc Monitor	PP
SIOL	Simulation Value Location	INLINK	Yes	0	No	No	N/A	No
SIML	Simulation Mode Location	INLINK	Yes	0	No	No	N/A	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

Three record support routines are provided: init_record, process, and get_value.

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 the type double constant, if non-zero, is converted to a string and stored into VAL 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.

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 Soft Output. If the return status of recGblGetLinkValue is zero then UDF is set to FALSE.
3. Check severity and write the new value. See Simulation Mode and Invalid Alarm Output Action for details on how the simulation mode and the INVALID alarm conditions affect output.
4. 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.
5. 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 OVAL is not equal to VAL.
   • NSEV and NSTA are reset to 0.
6. Scan forward link if necessary, set PACT FALSE, and return.

Device Support

Fields Of Interest To Device Support

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

Name	Summary	Description
PACT	Processing Active Field	See Fields Common to All Record Types for an explanation of these fields.
DPVT	Device Private
NSEV	New Alarm Severity
NSTA	New Alarm Status
VAL	Value	This is the field written by the device support routines.
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:

report

report(FILE fp, paddr)

Not currently used.

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_stringout

write_stringout(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 device support module writes the current value of VAL.

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

write_so calls recGblPutLinkValue to write the current value of VAL. See Soft Output.

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EPICS Record Reference Manual - 19 MAY 1998