Multi-Bit Binary Output Direct Record (mbboDirect)

The mbboDirect record performs the opposite function to that of the mbbiDirect record. It accumulates bits (in the fields B0 - BF) as unsigned characters, and converts them to a word which is then written out to hardware. If a bit field is non-zero, it is interpreted as a binary 1. On the other hand, if it is zero, it is interpreted as a binary 0.

Parameter Fields

The record-specific fields are described below, grouped by functionality.

Scan Parameters

The mbboDirect record has the standard fields for specifying under what circumstances it will be processed. These fields are listed in Scan Fields.

Desired Output Parameters

The mbboDirect record, like all output records, must specify where its output originates. The output mode select field (OMSL) 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 DOL field is ignored and the current value of VAL is used. The desired output can be written into the VAL field via dpPuts at run-time when the record is in supervisory mode. DOL can also be a constant, in which case VAL is initialized to the constant value. Note that OMSL cannot be closed_loop when DOL is a constant.

VAL is then converted to RVAL in the routine described in the next section. However, the Soft Channel device support module for the mbboDirect record writes the VAL field's value without any conversion.

FieldSummaryTypeDCT DefaultReadWriteCA PP
OMSLOutput Mode SelectMENU (menuOmsl)Yes YesYesYes
DOLDesired Output LocINLINKYes YesYesNo
VALWordLONGYes YesYesYes

Convert and Write Parameters

For records that are to write values to hardware devices, the OUT output link must contain the address of the I/O card, and the DTYP field must specify the proper 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.

If the mbboDirect record does not use the Soft Channel device support module, then VAL is converted to RVAL, and RVAL is the actual 16-bit word sent out. RVAL is set equal to VAL and then shifted left by the number of bits specified in the SHFT field (the SHFT value is set by device support and is not configurable by the user). RVAL is then sent out to the location specified in the OUT field.

For mbboDirect records that specify a database link, a channel access link, or a constant, the DTYP field must specify either one of two soft device support routines--{Soft Channel} or Raw Soft Channel. The difference between the two is that Soft Channel writes the desired output value from VAL directly to the output link while Raw Soft Channel writes the value from RVAL to the output link after it has undergone the conversion described above.

FieldSummaryTypeDCT DefaultReadWriteCA PP
OUTOutput SpecificationOUTLINKYes YesYesNo
B0Bit 0UCHARYes YesYesYes
B1Bit 1UCHARYes YesYesYes
B2Bit 2UCHARYes YesYesYes
B3Bit 3UCHARYes YesYesYes
B4Bit 4UCHARYes YesYesYes
B5Bit 5UCHARYes YesYesYes
B6Bit 6UCHARYes YesYesYes
B7Bit 7UCHARYes YesYesYes
B8Bit 8UCHARYes YesYesYes
B9Bit 9UCHARYes YesYesYes
BABit 10UCHARYes YesYesYes
BBBit 11UCHARYes YesYesYes
BCBit 12UCHARYes YesYesYes
BDBit 13UCHARYes YesYesYes
BEBit 14UCHARYes YesYesYes
BFBit 15UCHARYes YesYesYes

Operator Display Parameters

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

FieldSummaryTypeDCT DefaultReadWriteCA PP
NAMERecord NameSTRING [61]No YesNoNo
DESCDescriptorSTRING [41]Yes YesYesNo

Run-time Parameters

These parameters are used by the run-time code for processing the mbbo Direct record.

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

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

FieldSummaryTypeDCT DefaultReadWriteCA PP
NOBTNumber of BitsSHORTYes YesNoNo
ORAWPrev Raw ValueULONGNo YesNoNo
MASKHardware MaskULONGNo YesNoNo
MLSTLast Value MonitoredLONGNo YesNoNo

Simulation Mode Parameters

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

If SIMM (fetched through SIML) is YES, the record is put in SIMS severity and the value is written through SIOL, without conversion. 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.

FieldSummaryTypeDCT DefaultReadWriteCA PP
SIMLSimulation Mode LinkINLINKYes YesYesNo
SIMMSimulation ModeMENU (menuYesNo)No YesYesNo
SIOLSimulation Output LinkOUTLINKYes YesYesNo
SIMSSimulation Mode SeverityMENU (menuAlarmSevr)Yes YesYesNo
SDLYSim. Mode Async DelayDOUBLEYes-1.0YesYesNo
SSCNSim. Mode ScanMENU (menuScan)Yes65535YesYesNo

Alarm Parameters

The possible alarm conditions for mbboDirect records are the SCAN, READ, and INVALID alarms. The SCAN and READ alarms are not configurable by the user since they are always of MAJOR severity. See "Alarm Specification" for a complete explanation of Scan and Read alarms.

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, or Set output to IVOV. When Set output to IVOV is specified and a INVALID alarm is triggered, the record will write the value in the IVOV field to output. See Invalid Output Action Fields for more information. Alarm Fields lists the fields related to alarms that are common to all record types.

FieldSummaryTypeDCT DefaultReadWriteCA PP
IVOAINVALID outpt actionMENU (menuIvoa)Yes YesYesNo
IVOVINVALID output valueLONGYes YesYesNo

Record Support

Record Support Routines


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.

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


See next section.

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
      • Get value from DOL
      • Set PACT to FALSE
  3. Convert
    • If PACT is FALSE, compute RVAL
      • Set RVAL = VAL
      • Shift RVAL left SHFT bits
    • Status=write_mbboDirect
  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 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.
  6. Scan forward link if necessary, set PACT FALSE, and return.

Device Support

Fields Of Interest To Device Support

Each mbboDirect 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_mbboDirect is called. The device support routines are primarily interested in the following fields:

FieldSummaryTypeDCT DefaultReadWriteCA PP
PACTRecord activeUCHARNo YesNoNo
NSEVNew Alarm SeverityMENU (menuAlarmSevr)No YesNoNo
NSTANew Alarm StatusMENU (menuAlarmStat)No YesNoNo
NOBTNumber of BitsSHORTYes YesNoNo
OUTOutput SpecificationOUTLINKYes YesYesNo
RBVReadback ValueULONGNo YesNoNo
MASKHardware MaskULONGNo YesNoNo

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.



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(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.



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

Device Support For Soft Records

This 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_mbboDirect calls recGblPutLinkValue to write the current value of VAL.

See Soft Output.