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Binary Output Record (bo)

The normal use for this record type is to store a simple bit (0 or 1) value to be sent to a Digital Output module. It can also be used to write binary values into other records via database or channel access links. This record can implement both latched and momentary binary outputs depending on how the HIGH field is configured.

Scan Parameters

The binary output record has the standard fields for specifying under what circumstances the record will be processed. These fields are described in Scan Fields.

Field Summary Type DCT Default Read Write CA PP
SCAN Scan Mechanism MENU menuScan Yes Yes Yes No
PHAS Scan Phase SHORT Yes Yes Yes No
EVNT Event Name STRING [40] Yes Yes Yes No
PRIO Scheduling Priority MENU menuPriority Yes Yes Yes No
PINI Process at iocInit MENU menuPini Yes Yes Yes No

Desired Output Parameters

The binary output record must specify where its desired output originates. The desired output needs to be in engineering units.

The first field that determines where the desired output originates is the output mode select (OMSL) field, which can have two possible values: losed_loop or supervisory. If supervisory is specified, the value in the VAL field can be set 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 Link (DOL) field which can be a database link or a channel access link, but not a constant. To achieve continuous control, a database link to a control algorithm record should be entered in the DOL field.

See Address Specification for information on hardware addresses and links.

Field Summary Type DCT Default Read Write CA PP
DOL Desired Output Link INLINK Yes Yes Yes No
OMSL Output Mode Select MENU menuOmsl Yes Yes Yes No

Convert and Write Parameters

These parameters are used to determine where the binary output writes to and how to convert the engineering units to a raw signal. After VAL is set and forced to be either 1 or 0, as the result of either a dbPut or a new value being retrieved from the link in the DOL field, then what happens next depends on which device support routine is used and how the HIGH field is configured.

If the Soft Channel device support routine is specified, then the device support routine writes the VAL field's value to the address specified in the OUT field. Otherwise, RVAL is the value written by the device support routines after being converted.

If VAL is equal to 0, then the record processing routine sets RVAL equal to zero. When VAL is not equal to 0, then RVAL is set equal to the value contained in the MASK field. (MASK is set by the device support routines and is of no concern to the user.) Also, when VAL is not 0 and after RVAL is set equal to MASK, the record processing routine checks to see if the HIGH field is greater than 0. If it is, then the routine will process the record again with VAL set to 0 after the number of seconds specified by HIGH. Thus, HIGH implements a momentary output which changes the state of the device back to 0 after N number of seconds.

Field Summary Type DCT Default Read Write CA PP
DTYP Device Type DEVICE Yes Yes Yes No
OUT Output Specification OUTLINK Yes Yes Yes No
VAL Current Value ENUM Yes Yes Yes Yes
RVAL Raw Value ULONG No Yes Yes Yes
HIGH Seconds to Hold High DOUBLE Yes Yes Yes No
ZNAM Zero Name STRING [26] Yes Yes Yes Yes
ONAM One Name STRING [26] Yes Yes Yes Yes

Conversion Parameters

The ZNAM field has the string that corresponds to the 0 state, and the ONAM field holds the string that corresponds to the 1 state. These fields, other than being used to tell the operator what each state represents, are used to perform conversions if the value fetched by DOL is a string. If it is, VAL is set to the state which corresponds to that string. For instance, if the value fetched is the string "Off" and the ZNAM string is "Off," then VAL is set to 0.

After VAL is set, if VAL is equal to 0, then the record processing routine sets RVAL equal to zero. When VAL is not equal to 0, then RVAL is set equal to the value contained in the MASK field. (Mask is set by the device support routines and is of no concern to the user.) Also when VAL is equal to 1 and after RVAL is set equal to MASK, the record processing routine checks to see if the HIGH field is greater than 0. If it is, then the routine processes the record again with VAL=0 after the number of seconds specified by HIGH. Thus, HIGH implements a latched output which changes the state of the device or link to 1, then changes it back to 0 after N number of seconds.

Field Summary Type DCT Default Read Write CA PP
ZNAM Zero Name STRING [26] Yes Yes Yes Yes
ONAM One Name STRING [26] Yes Yes Yes Yes
HIGH Seconds to Hold High DOUBLE Yes Yes Yes No

Output Specification

The OUT field specifies where the binary output record writes its output. It must specify the address of an I/O card if the record sends its output to hardware, and the DTYP field must contain the corresponding device support module. Be aware that the address format differs according to the I/O bus used. See Address Specification for information on the format of hardware addresses.

Otherwise, if the record is configured to use the soft device support modules, then it can be either a database link, a channel access link, or a constant. Be aware that nothing will be written when OUT is a constant. See Address Specification for information on the format of the database and channel access addresses. Also, see "Device Support For Soft Records" in this chapter for more on output to other records.

Operator Display Parameters

These parameters are used to present meaningful data to the operator, The get_enum_str() record support routine can retrieve the state string corresponding to the VAL's state. So, if the value is 1, get_enum_str() will return the string in the ONAM field: and if 0, get_enum_str() will return the ZNAM string.

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

Field Summary Type DCT Default Read Write CA PP
ZNAM Zero Name STRING [26] Yes Yes Yes Yes
ONAM One Name STRING [26] Yes Yes Yes Yes
NAME Record Name STRING [61] No Yes No No
DESC Descriptor STRING [41] Yes Yes Yes No

Alarm Parameters

These parameters are used to determine the binary output's alarm condition and to determine the severity of that condition. The possible alarm conditions for binary outputs are the SCAN, READ, INVALID and state alarms. The user can configure the state alarm conditions using these fields.

The possible values for these fields are NO_ALARM, MINOR, and MAJOR. The ZSV holds the severity for the zero state; OSV for the one state. COSV is used to cause an alarm whenever the state changes between states (0-1, 1-0) and its severity is configured as MINOR or MAJOR.

See Invalid Output Action Fields for more information on the IVOA and IVOV fields. Alarm Fields lists other fields related to alarms that are common to all record types.

Field Summary Type DCT Default Read Write CA PP
ZSV Zero Error Severity MENU menuAlarmSevr Yes Yes Yes Yes
OSV One Error Severity MENU menuAlarmSevr Yes Yes Yes Yes
COSV Change of State Sevr MENU menuAlarmSevr Yes Yes Yes Yes
IVOA INVALID outpt action MENU menuIvoa Yes Yes Yes No
IVOV INVALID output value USHORT Yes Yes Yes No

Run-Time Parameters

These parameters are used by the run-time code for processiong the binary output. They are not configurable using a configuration tool. They represent the current state of the binary output.

ORAW is used to determine if monitors should be triggered for RVAL at the same time they are triggered for VAL.

MASK is given a value by the device support routines and should not concern the user.

The RBV field is also set by device support. It is the actual read back value obtained from the hardware itself or from the associated device driver.

The ORBV field is used to decide if monitors should be triggered for RBV at the same time monitors are triggered for changes in VAL.

The LALM field holds the value of the last occurrence of the change of state alarm. It is used to implement the change of state alarm, and thus only has meaning if COSV is MINOR or MAJOR.

The MLST is used by the process() record support routine to determine if archive and value change monitors are invoked. They are if MLST is not equal to VAL.

The WPDT field is a private field for honoring seconds to hold HIGH.

Field Summary Type DCT Default Read Write CA PP
ORAW prev Raw Value ULONG No Yes No No
MASK Hardware Mask ULONG No Yes No No
RBV Readback Value ULONG No Yes No No
ORBV Prev Readback Value ULONG No Yes No No
LALM Last Value Alarmed USHORT No Yes No No
MLST Last Value Monitored USHORT No Yes No No
RPVT Record Private NOACCESS No No No No
WDPT Watch Dog Timer ID NOACCESS No No No No

Simulation Mode Parameters

The following fields are used to operate the record in simulation mode.

If SIMM (fetched through SIML, if populated) is YES, the record is put in SIMS severity and the unconverted value is written through SIOL. If SIMM is RAW, the value is converted and RVAL is written. SSCN sets a different SCAN mechanism to use in simulation mode. SDLY sets a delay (in sec) that is used for asynchronous simulation processing.

See Output Simulation Fields for more information on simulation mode and its fields.

Field Summary Type DCT Default Read Write CA PP
SIML Simulation Mode Link INLINK Yes Yes Yes No
SIMM Simulation Mode MENU menuSimm No Yes Yes No
SIOL Simulation Output Link OUTLINK Yes Yes Yes No
SIMS Simulation Mode Severity MENU menuAlarmSevr Yes Yes Yes No
SDLY Sim. Mode Async Delay DOUBLE Yes -1.0 Yes Yes No
SSCN Sim. Mode Scan MENU menuScan Yes 65535 Yes Yes 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 a 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, and error message is issued and processing is terminated.

If DOL is a constant, then VAL is initialized to 1 if its value is nonzero or initialzed to 0 if DOL is zero, and UDF is set to FALSE.

If device support includes init_record(), it is called. VAL is set using RVAL, and UDF is set to FALSE.

process

See next section.

get_enum_str

Retrieves ASCII string corresponding to VAL.

get_enum_strs

Retrieves ASCII strings for ZNAM and ONAM.

put_enum_str

Checks if string matches ZNAM or ONAM, and if it does, sets VAL.

Record Processing

Routine process implements the following algorithm:

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.

If PACT is FALSE

  • If DOL holds a link and OMSL is closed_loop

    • get values from DOL
    • check for link alarm
    • force VAL to be 0 or 1
    • if MASK is defined
      • if VAL is 0 set RVAL = 0
    • else set RVAL = MASK

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.

Check severity and write the new value. See Invalid Output Action Fields for more information on how INVALID alarms affect output.

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.

Check WAIT. If VAL is 1 and WAIT is greater than 0, process again with a VAL=0 after WAIT seconds.

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 MLST is not equal to VAL.

  • Monitors for RVAL and for RBV are checked whenever other monitors are invoked.

  • NSEV and NSTA are reset to 0.

  • 8 Scan forward link if necessary, set PACT FALSE, and return

Device support

Fields Of Interest To Device Support

Each binary 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_bo() is called. The device support routines are primarily interested in the following fields:

Field Summary Type DCT Default Read Write CA PP
PACT Record active UCHAR No Yes No No
DPVT Device Private NOACCESS No No No No
NSEV New Alarm Severity MENU menuAlarmSevr No Yes No No
NSTA New Alarm Status MENU menuAlarmStat No Yes No No
VAL Current Value ENUM Yes Yes Yes Yes
OUT Output Specification OUTLINK Yes Yes Yes No
RVAL Raw Value ULONG No Yes Yes Yes
MASK Hardware Mask ULONG No Yes No No
RBV Readback Value ULONG No Yes No No

Device Support Routines

Device support consists of the following routines:

long report(int level)

This optional routine is called by the IOC command dbior and is passed the report level that was requested by the user. It should print a report on the state of the device support to stdout. The level parameter may be used to output increasingly more detailed information at higher levels, or to select different types of information with different levels. Level zero should print no more than a small summary.

long init(int after)

This optional routine is called twice at IOC initialization time. The first call happens before any of the init_record() calls are made, with the integer parameter after set to 0. The second call happens after all of the init_record() calls have been made, with after set to 1.

init_record(precord)

This routine is optional. If provided, it is called by record support init_record() routine. It should determine MASK if it is needed.

  • 0: Success. RVAL modified (VAL will be set accordingly)
  • 2: Success. VAL modified
  • other: Error

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_bo(precord)

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

  • 0: Success
  • other: Error.

Device Support For Soft Records

Two soft device support modules Soft Channel and Raw Soft Channel are provided for output records not related to actual hardware devices. The OUT link type must be either CONSTANT, DB_LINK, or CA_LINK.

Soft Channel

This module writes the current value of VAL.

If the OUT link type is PV_LINK, then dbCaAddInlink() is called by init_record(). init_record() always returns a value of 2, which means that no conversion will ever be attempted. write_bo() calls recGblPutLinkValue() to write the current value of VAL. See "Soft Output" for details.

Raw Soft Channel

This module is like the previous except that it writes the current value of RVAL