Array Analog Input (aai)

The array analog input record type is used to read array data. The array data can contain any of the supported data types. The record is in many ways similar to the waveform record. It allows, however, the device support to allocate the array storage.

Parameter Fields

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

Scan Parameters

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

Read Parameters

These fields are configurable by the user to specify how and from where the record reads its data. The INP field determines from where the array analog input gets its input. It can be a hardware address, a channel access or database link, or a constant. Only in records that use soft device support can the INP field be a channel access link, a database link, or a constant. Otherwise, the INP field must be a hardware address.

Fields related to waveform reading

The DTYP field must contain the name of the appropriate device support module. The values retrieved from the input link are placed in an array referenced by VAL. (If the INP link is a constant, elements can be placed in the array via dbPuts.) NELM specifies the number of elements that the array will hold, while FTVL specifies the data type of the elements (follow the link in the table below for a list of the available choices).

FieldSummaryTypeDCT DefaultReadWriteCA PP
DTYPDevice TypeDEVICEYes YesYesNo
INPInput SpecificationINLINKYes YesYesNo
NELMNumber of ElementsULONGYes1YesNoNo
FTVLField Type of ValueMENU (menuFtype)Yes YesNoNo

Operator Display Parameters

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

Fields related to Operator Display

EGU is a string of up to 16 characters describing the units that the array data measures. It is retrieved by the get_units() record support routine.

The HOPR and LOPR fields set the upper and lower display limits for array elements referenced by the VAL field. Both the get_graphic_double() and get_control_double() record support routines retrieve these fields.

The PREC field determines the floating point precision with which to display the array values. It is used whenever the get_precision() record support routine is called.

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

FieldSummaryTypeDCT DefaultReadWriteCA PP
EGUEngineering UnitsSTRING [16]Yes YesYesNo
HOPRHigh Operating RangeDOUBLEYes YesYesNo
LOPRLow Operating RangeDOUBLEYes YesYesNo
PRECDisplay PrecisionSHORTYes YesYesNo
NAMERecord NameSTRING [61]No YesNoNo
DESCDescriptorSTRING [41]Yes YesYesNo

Alarm Parameters

The array analog input record has the alarm parameters common to all record types.

Monitor Parameters

These parameters are used to determine when to send monitors placed on the VAL field. The APST and MPST fields are a menu with choices Always and On Change. The default is Always, thus monitors will normally be sent every time the record processes. Selecting On Change causes a 32-bit hash of the VAL field buffer to be calculated and compared with the previous hash value every time the record processes; the monitor will only be sent if the hash is different, indicating that the buffer has changed. Note that there is a small chance that two different value buffers might result in the same hash value, so for critical systems Always may be a better choice, even though it re-sends duplicate data.

FieldSummaryTypeDCT DefaultReadWriteCA PP
APSTPost Archive MonitorsMENU (aaiPOST)Yes YesYesNo
MPSTPost Value MonitorsMENU (aaiPOST)Yes YesYesNo
HASHHash of OnChange data.ULONGNo YesYesNo

Menu aaiPOST

These are the possible choices for the APST and MPST fields:

IndexIdentifierChoice String
0 aaiPOST_Always Always
1 aaiPOST_OnChange On Change

Run-time Parameters

These parameters are used by the run-time code for processing the array analog input record. They are not configured using a configuration tool. Only the VAL field is modifiable at run-time.

VAL references the array where the array analog input record stores its data. The BPTR field holds the address of the array.

The NORD field holds a counter of the number of elements that have been read into the array.

FieldSummaryTypeDCT DefaultReadWriteCA PP
NORDNumber elements readULONGNo 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 fetched through SIOL. 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 Input Simulation Fields for more information on simulation mode and its fields.

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

Record Support

Record Support Routines


   static long init_record(aaiRecord *prec, int pass)

If device support includes an init_record() routine it is called, but unlike most record types this occurs in pass 0, which allows the device support to allocate the array buffer itself.

Since EPICS 7.0.5 the device support may return AAI_DEVINIT_PASS1 to request a second call to its init_record() routine in pass 1.

Checks if device support allocated array space. If not, space for the array is allocated using NELM and FTVL. The array address is stored in BPTR.

This routine initializes SIMM with the value of SIML if SIML type is CONSTANT link or creates a channel access link if SIML type is PV_LINK. VAL is likewise initialized if SIOL is CONSTANT or PV_LINK.

This routine next checks to see that device support is available and a device support read routine is defined. If either does not exist, an error message is issued and processing is terminated


  static long process(aaiRecord *prec)

See "Record Processing" section below.


  static long cvt_dbaddr(DBADDR *paddr)

This is called by dbNameToAddr. It makes the dbAddr structure refer to the actual buffer holding the result.


  static long get_array_info(DBADDR *paddr, long *no_elements, long *offset)

Obtains values from the array referenced by VAL.


  static long put_array_info(DBADDR *paddr, long nNew)

Writes values into the array referenced by VAL.


  static long get_units(DBADDR *paddr, char *units)

Retrieves EGU.


  static long get_precision(DBADDR *paddr, long *precision)

Retrieves PREC if field is VAL field. Otherwise, calls recGblGetPrec().


  static long get_graphic_double(DBADDR *paddr, struct dbr_grDouble *pgd)

Sets the upper display and lower display limits for a field. If the field is VAL 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.

Sets the following values:

  upper_disp_limit = HOPR
  lower_disp_limit = LOPR


  static long get_control_double(DBADDR *paddr, struct dbr_ctrlDouble *pcd)

Sets the upper control and the lower control limits for a field. If the field is VAL 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.

Sets the following values

  upper_ctrl_limit = HOPR
  lower_ctrl_limit = LOPR

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. Call device support read routine read_aai().
  3. If PACT has been changed to TRUE, the device support read routine has started but has not completed writing the new value. In this case, the processing routine merely returns, leaving PACT TRUE.
  4. 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 APST or MPST are Always or if the result of the hash calculation is different.
    • NSEV and NSTA are reset to 0.
  5. Scan forward link if necessary, set PACT FALSE, and return.

Device Support

Fields Of Interest To Device Support

Each array analog input record record must have an associated set of device support routines. The primary responsibility of the device support routines is to obtain a new array value whenever read_aai() 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
INPInput SpecificationINLINKYes YesYesNo
NELMNumber of ElementsULONGYes1YesNoNo
FTVLField Type of ValueMENU (menuFtype)Yes YesNoNo
NORDNumber elements readULONGNo 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.


  long init_record(dbCommon *precord)

This routine is optional. If provided, it is called by the record support's init_record() routine in pass 0. The device support may allocate memory for the VAL field's array (enough space for NELM elements of type FTVA) from its own memory pool if desired, and store the pointer to this buffer in the BPTR field. The record will use calloc() for this memory allocation if BPTR has not been set by this routine. The routine must return 0 for success, -1 or a error status on failure.

Since EPICS 7.0.5 if this routine returns AAI_DEVINIT_PASS1 in pass 0, it will be called again in pass 1 with the PACT field set to AAI_DEVINIT_PASS1. In pass 0 the PACT field is set to zero (FALSE).


  long get_ioint_info(int cmd, 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.


  long read_aai(dbCommon *precord)

This routine should provide a new input value. It returns the following values:

Device Support For Soft Records

The Soft Channel device support is provided to read values from other records via the INP link, or to hold array values that are written into it.

If INP is a constant link the array value gets loaded from the link constant by the record_init() routine, which also sets NORD. The read_aai() routine does nothing in this case.

If INP is a database or channel access link, the read_aai() routine gets a new array value from the link and sets NORD.