RRM 3-14 Multi-Bit Binary Output

EPICS Record Reference Manual

mbbo -- Multi-Bit Binary Output

The normal use for the mbbo record type is to send a binary value (representing one of up to 16 states) to a Digital Output module. It is used for any device that uses more than one bit to control it. The mbbo record can also be used to write discrete values to other records via database or channel access links.

Parameter Fields

The multi-bit binary output fields fall into the following categories:

• scan parameters
• desired output parameters
• write and convert parameters
• operator display parameters
• alarm parameters
• run-time parameters

Scan Parameters

The mbbo 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 multi-bit binary output record, like all output records, must specify where its output originates. The output mode select (OMSL) field determines whether the output originates from another record or from database access (i.e., the operator). 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 DOL field is ignored and the current value of VAL is simply written. VAL can be changed via dpPuts at run-time when OMSL is supervisory. The DOL field can also be a constant, in which case the VAL field is initialized to the constant value. If DOL is a constant, OMSL cannot be set to closed_loop.

The VAL field itself usually consists of an index that specifies one of the states. The actual output written is the value of RVAL, which is converted from VAL following the routine explained in the next section. However, records that use the Soft Channel device support module write the VAL field's value without any conversion.

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

Convert and Write Parameters

The device support routines write the desired output to the location specified in the OUT field. If the record uses soft device support, OUT can contain a constant, a database link, or a channel access link; however, if OUT is a constant, no value will be written.

For records that write their values to hardware devices, the OUT output link must specify the address of the I/O card, and the DTYP field must specify 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. The user 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 mbbo records that write to hardware, the value written to the output location is the value contained in RVAL, which is converted from VAL, VAL containing an index of one of the 16 states (0-15). RVAL is then set to the corresponding state value, the value in one of the fields ZRVL through FFVL. Then this value is shifted left according to the number in the SHFT field so that the value is in the correct position for the bits being used (the SHFT value is set by device support and is not configurable by the user).

The state value fields ZRVL through FFVL must be configured by the user before run-time. When the state values are not defined, the states defined (SDEF) field is set to FALSE at initialization time by the record routines. When SDEF is FALSE, then the record processing routine does not try to find a match, RVAL is set equal to VAL, the bits are shifted using the number in SHFT, and the value is written thus.

If the OUT output link specifies a database link, channel access link, or constant, then the DTYP field must specify either one of the two soft device support modules--Soft Channel or Raw Soft Channel. Soft Channel writes the value of VAL to the output link, without any conversion, while Raw Soft Channel writes the value from RVAL after it has undergone the above conversion. See Address Specification for information on specifying links.

Note also that when a string is retrieved as the desired output, a record support routine is provided (put_enum_str) that will set check to see if the string matches one of the strings in the ZRST through FFST fields. If a match is found, RVAL is set equal to the corresponding state value of that string.

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
RVAL	Raw Data Value	ULONG	No	0	Yes	Yes	Yes	Yes
SHFT	Shift	USHORT	No	0	Yes	No	No	No
SDEF	States Defined?	SHORT	No	0	Yes	No	No	No
ZRVL	Zero Value	ULONG	Yes	0	Yes	Yes	No	Yes
ONVL	One value	ULONG	Yes	0	Yes	Yes	No	Yes
TWVL	Two Value	ULONG	Yes	0	Yes	Yes	No	Yes
THVL	Three Value	ULONG	Yes	0	Yes	Yes	No	Yes
FRVL	Four Value	ULONG	Yes	0	Yes	Yes	No	Yes
FVVL	Five Value	ULONG	Yes	0	Yes	Yes	No	Yes
SXVL	Six Value	ULONG	Yes	0	Yes	Yes	No	Yes
SVVL	Seven Value	ULONG	Yes	0	Yes	Yes	No	Yes
EIVL	Eight value	ULONG	Yes	0	Yes	Yes	No	Yes
NIVL	Nine Value	ULONG	Yes	0	Yes	Yes	No	Yes
TEVL	Ten Value	ULONG	Yes	0	Yes	Yes	No	Yes
ELVL	Eleven Value	ULONG	Yes	0	Yes	Yes	No	Yes
TVVL	Twelve Value	ULONG	Yes	0	Yes	Yes	No	Yes
TTVL	Thirteen Value	ULONG	Yes	0	Yes	Yes	No	Yes
FTVL	Fourteen Value	ULONG	Yes	0	Yes	Yes	No	Yes
FFVL	Fifteen Value	ULONG	Yes	0	Yes	Yes	No	Yes
ZRST	Zero String	STRING [16]	Yes	Null	Yes	Yes	No	Yes
ONST	One String	STRING [16]	Yes	Null	Yes	Yes	No	Yes
TWST	Two String	STRING [16]	Yes	Null	Yes	Yes	No	Yes
THST	Three String	STRING [16]	Yes	Null	Yes	Yes	No	Yes
FRST	Four String	STRING [16]	Yes	Null	Yes	Yes	No	Yes
FVST	Five String	STRING [16]	Yes	Null	Yes	Yes	No	Yes
SXST	Six String	STRING [16]	Yes	Null	Yes	Yes	No	Yes
SVST	Seven String	STRING [16]	Yes	Null	Yes	Yes	No	Yes
EIST	Eight String	STRING [16]	Yes	Null	Yes	Yes	No	Yes
NIST	Nine String	STRING [16]	Yes	Null	Yes	Yes	No	Yes
TEST	Ten String	STRING [16]	Yes	Null	Yes	Yes	No	Yes
ELST	Eleven String	STRING [16]	Yes	Null	Yes	Yes	No	Yes
TVST	Twelve String	STRING [16]	Yes	Null	Yes	Yes	No	Yes
TTST	Thirteen String	STRING [16]	Yes	Null	Yes	Yes	No	Yes
FTST	Fourteen String	STRING [16]	Yes	Null	Yes	Yes	No	Yes
FFST	Fifteen String	STRING [16]	Yes	Null	Yes	Yes	No	Yes

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 mbbo record either textually or graphically. The ZRST-FFST fields contain strings describing each of the corresponding states. The get_enum_str and get_enum_strs record routines retrieve these strings for the operator. Get_enum_str gets the string corresponding to the value set in VAL, and get_enum_strs retrieves all the strings.

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
ZRST,...,FFST	Zero String, One String, ...	STRING [16]	Yes	Null	Yes	Yes	No	Yes
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 multi-bit binary outputs are the SCAN, READ, INVALID, and state alarms. The SCAN and READ alarms are called by the support modules and are not configurable by the user, as their severity is always MAJOR.

The IVOA field specifies an action to take from a number of possible choices when the INVALID alarm is triggered. The IVOV field contains a value to be written once the INVALID alarm has been triggered if Set output to IVOV has been chosen in the IVOA field. The severity of the INVALID alarm is not configurable by the user.

The state alarms are configured in the below severity fields. These fields have the usual possible values for severity fields: NO ALARM, MINOR, and MAJOR.

The unknown state severity field (UNSV), if set to MINOR or MAJOR, triggers an alarm when the record support routine cannot find a matching value in the state value fields for VAL or when VAL is out of range.

The change of state severity field (COSV) triggers an alarm when the record's state changes, if set to MAJOR or MINOR.

The state severity (ZRSV-FFSV) fields, when set to MAJOR or MINOR, trigger an alarm when VAL equals the corresponding field.

See Alarm Specification for a complete explanation of discrete alarms and these fields. See Invalid Alarm Output Action for an explanation of 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
UNSV	Unknown State Severity	GBLCHOICE	Yes	0	Yes	Yes	No	Yes
COSV	Change of State Severity	GBLCHOICE	Yes	0	Yes	Yes	No	Yes
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
ZRSV	0 State Severity	GBLCHOICE	Yes	0	Yes	Yes	No	Yes
ONSV	1 State Severity	GBLCHOICE	Yes	0	Yes	Yes	No	Yes
TWSV	2 State Severity	GBLCHOICE	Yes	0	Yes	Yes	No	Yes
THSV	3 State Severity	GBLCHOICE	Yes	0	Yes	Yes	No	Yes
FRSV	4 State Severity	GBLCHOICE	Yes	0	Yes	Yes	No	Yes
FVSV	5 State Severity	GBLCHOICE	Yes	0	Yes	Yes	No	Yes
SXSV	6 State Severity	GBLCHOICE	Yes	0	Yes	Yes	No	Yes
SVSV	7 State Severity	GBLCHOICE	Yes	0	Yes	Yes	No	Yes
EISV	8 State Severity	GBLCHOICE	Yes	0	Yes	Yes	No	Yes
NISV	9 State Severity	GBLCHOICE	Yes	0	Yes	Yes	No	Yes
TESV	10 State Severity	GBLCHOICE	Yes	0	Yes	Yes	No	Yes
ELSV	11 State Severity	GBLCHOICE	Yes	0	Yes	Yes	No	Yes
TVSV	12 State Severity	GBLCHOICE	Yes	0	Yes	Yes	No	Yes
TTSV	13 State Severity	GBLCHOICE	Yes	0	Yes	Yes	No	Yes
FTSV	14 State Severity	GBLCHOICE	Yes	0	Yes	Yes	No	Yes
FFSV	15 State Severity	GBLCHOICE	Yes	0	Yes	Yes	No	Yes

Run-Time and Simulation Mode Parameters

These parameters are used by the run-time code for processing the multi-bit binary output.

MASK is used by device support routine to read the hardware register. Record support sets low order of MASK the number of bits specified in NOBT. Device support can shift this value.

The LALM field implements the change of state alarm severity by holding the value of VAL when the previous change of state alarm was issued.

MLST holds the value when the last monitor for value change was triggered.

SDEF is used by record support to save time if no states are defined; it is used for converting VAL to RVAL.

Field	Summary	Type	DCT	Initial	Access	Modify	Rec Proc Monitor	PP
NOBT	Number of Bits	SHORT	Yes	0	Yes	No	No
ORAW	Old Raw Data	ULONG	No	0	Yes	No	No	No
MASK	Mask	ULONG	No	0	Yes	No	No	No
LALM	Last Alarmed	USHORT	No	0	Yes	No	No	No
MLST	Monitor Last	USHORT	No	0	Yes	No	No	No
SDEF	States Defined?	SHORT	No	0	Yes	No	No	No

The following fields are used to operate the mbbo record 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	No	No	N/A	No
SVAL	Simulation Value	DOUBLE	No	0	Yes	Yes	No	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

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.

MASK is cleared and then the NOBT low order bits are set.

If device support includes init_record, it is called.

init_common is then called to determine if any states are defined. If states are defined, SDEF is set to TRUE.

If device support returns success, VAL is then set from RVAL and UDF is set to FALSE.

process

See next section.

special

Computes SDEF when any of the fields ZRVL,...FFVL change value.

get_value

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

get_enum_str

Retrieves ASCII string corresponding to VAL.

get_enum_strs

Retrieves ASCII strings for ZRST,...FFST.

put_enum_str

Checks if string matches ZRST,...FFST and if it does, sets 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 not longer be called for this record. Thus error storms will not occur.
2. If PACT is FALSE
   • If DOL is DB_LINK and OMSL is CLOSED_LOOP
     • Get value from DOL
     • Set UDF to FALSE
     • Check for link alarm
   • If any state values are defined
     • If VAL > 15, then raise alarm and go to 4
     • Else using VAL as index set RVAL = one of ZRVL,...FFVL
   • Else set RVAL = VAL
   • Shift RVAL left SHFT bits
3. Convert
   • If PACT is FALSE, compute RVAL
     • If VAL is 0,...,15, set RVAL from ZRVL,...,FFVL
     • If VAL out of range, set RVAL = undefined
   • Status = write_mbbo
4. 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.
5. Check severity and write the new value. See Simulation Mode and Invalid Alarm Output Action for more information.
6. 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.
7. 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 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 mbbo record must have an associated set of device support routines. The primary responsibility of the device support routines is to obtain a new raw mbbo value whenever write_mbbo 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
NOBT	Number of Bits	Number of hardware bits accessed. They must be consecutive.
OUT	Output Link	This field is used by the device support routines to locate its output.
RVAL	Raw data value.	This is the value to be written to OUT.
RBV	Read Back Value	It is the responsibility of the device support modules to set this field.
MASK	Mask	This is a mask used to read the hardware. Record support sets the low order NOBT bits. The device support routine can shift the bits. The device support routine should perform the shift in init_record.
SHFT	Shift	This can be set by the device support module at init_record time.

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. If MASK is used, it should be shifted if necessary and SHFT given a value.

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_mbbo

write_mbbo(precord)

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

• 0: Success.
• Other: Error.

Device Support For Soft Records

Soft Channel

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_mbbo calls recGblPutLinkValue to write the current value of VAL. See Soft Output for more information.

Raw Soft Channel

This module writes RVAL to the location specified in the output link. It returns a 0.

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EPICS Record Reference Manual - 19 MAY 1998