The Calculation Output or "Calcout" record is similar to the Calc record with the added feature of having outputs (an "output link" and an "output event") which are conditionally executed based on the result of the calculation. This feature allows conditional branching to be implemented within an EPICS database (e.g. process Record_A only if Record_B has a value of 0). The Calcout record is also similar to the Wait record (with additional features) but uses EPICS standard INLINK and OUTLINK fields rather than the DBF_STRING fields used in the Wait record. For new databases, it is recommended that the Calcout record be used instead of the Wait record.
The record-specific fields are described below, grouped by functionality.
The Calcout record has the standard fields for specifying under what circumstances the record will be processed. These fields are listed in Scan Fields.
The read parameters for the Calcout record consists of 12 input links INPA,
INPB,
...
INPL.
The fields can be database links,
channel access links,
or constants.
If they are links,
they must specify another record's field.
If they are constants,
they will be initialized with the value they are configured with and can be changed via dbPuts.
These fields cannot be hardware addresses.
In addition,
the Calcout record contains the INAV,
INBV,
...
INLV fields which indicate the status of the link fields,
for example,
whether or not the specified PV was found and a link to it established.
See "Operator Display Parameters" for an explanation of these fields.
Field Summary Type DCT Default Read Write CA PP INPA Input A INLINK Yes Yes Yes No INPB Input B INLINK Yes Yes Yes No INPC Input C INLINK Yes Yes Yes No INPD Input D INLINK Yes Yes Yes No INPE Input E INLINK Yes Yes Yes No INPF Input F INLINK Yes Yes Yes No INPG Input G INLINK Yes Yes Yes No INPH Input H INLINK Yes Yes Yes No INPI Input I INLINK Yes Yes Yes No INPJ Input J INLINK Yes Yes Yes No INPK Input K INLINK Yes Yes Yes No INPL Input L INLINK Yes Yes Yes No
Like the Calc record, the Calcout record has a CALC field in which the developer can enter an infix expression which the record routine will evaluate when it processes the record. The resulting value is placed in the VAL field. This value can then be used by the OOPT field (see "Output Parameters") to determine whether or not to write to the output link or post an output event. It can also be the value that is written to the output link. The CALC expression is actually converted to opcode and stored in Reverse Polish Notation in the RPCL field. It is this expression which is actually used to calculate VAL. The Reverse Polish expression is evaluated more efficiently during run-time than an infix expression. CALC can be changes at run-time, and a special record routine will call a function to convert it to Reverse Polish Notation.
The infix expressions that can be used are very similar to the C expression syntax, but with some additions and subtle differences in operator meaning and precedence. The string may contain a series of expressions separated by a semi-colon character ';' any one of which may actually provide the calculation result; however all of the other expressions included must assign their result to a variable. All alphabetic elements described below are case independent, so upper and lower case letters may be used and mixed in the variable and function names as desired. Spaces may be used anywhere within an expression except between the characters that make up a single expression element.
The range of expressions supported by the calculation record are separated into literals, constants, operands, algebraic operators, trigonometric operators, relational operators, logical operator, the assignment operator, parentheses and commas, and the question mark or '?:' operator.
Field Summary Type DCT Default Read Write CA PP CALC Calculation STRING [80] Yes Yes Yes Yes VAL Result DOUBLE Yes Yes Yes No RPCL Reverse Polish Calc NOACCESS No No No No
The expression can use the values retrieved from the INPx links as operands, though constants can be used as operands too. These values retrieved from the input links are stored in the A-L fields. The values to be used in the expression are simple references by the field letter. For instance, the value obtained from the INPA link is stored in field A, and the values obtained from the INPB link is stored in the field B. The names can be included in the expression will operate on their respective values, as in A+B.
Field Summary Type DCT Default Read Write CA PP A Value of Input A DOUBLE No Yes Yes Yes B Value of Input B DOUBLE No Yes Yes Yes C Value of Input C DOUBLE No Yes Yes Yes D Value of Input D DOUBLE No Yes Yes Yes E Value of Input E DOUBLE No Yes Yes Yes F Value of Input F DOUBLE No Yes Yes Yes G Value of Input G DOUBLE No Yes Yes Yes H Value of Input H DOUBLE No Yes Yes Yes I Value of Input I DOUBLE No Yes Yes Yes J Value of Input J DOUBLE No Yes Yes Yes K Value of Input K DOUBLE No Yes Yes Yes L Value of Input L DOUBLE No Yes Yes Yes
The keyword VAL returns the current contents of the expression's result field, i.e. the VAL field for the CALC expression and the OVAL field for the OCAL expression. (These fields can be written to by CA put, so it might not be the result from the last time the expression was evaluated).
>= : Greater than or equal to> : Greater than<= : Less than or equal to< : Less than# : Not equal to= : Equal to| : Bitwise Or& : Bitwise And~ : One's Complement<< : Arithmetic Left Shift>> : Arithmetic Right Shift>>> : Logical Right Shift:= : assigns a value (right hand side) to a variable (i.e.
field)The open and close parentheses are supported. Nested parentheses are supported.
The comma is supported when used to separate the arguments of a binary function.
The semicolon is used to separate expressions. Although only one traditional calculation expression is allowed, multiple assignment expressions are allowed.
The C language's question mark operator is supported.
The format is: condition ?
True result : False result
A + B + 10
A + B + 10(A + B) < (C + D)
(A + B) < (C + D)(A + B) >= (C + D)(A + B) < (C + D) ?
E : F + L + 10
E if (A + B) < (C + D)F + L + 10 if (A + B) >= (C + D)Prior to Base 3.14.9 it was legal to omit the : and the second (else) part of the conditional, like this:
(A + B)<(C + D) ?
E
From 3.14.9 onwards,
this expression must be written as (A + B) < (C + D) ?
E : VAL
A & B
sin(a); a:=a+D2R
These parameters specify and control the output capabilities of the Calcout record. They determine when to write the output, where to write it, and what the output will be. The OUT link specifies the Process Variable to which the result will be written.
The OOPT field determines the condition that causes the output link to be written to. It's a menu field that has six choices:
Index Identifier Choice String 0 calcoutOOPT_Every_Time Every Time 1 calcoutOOPT_On_Change On Change 2 calcoutOOPT_When_Zero When Zero 3 calcoutOOPT_When_Non_zero When Non-zero 4 calcoutOOPT_Transition_To_Zero Transition To Zero 5 calcoutOOPT_Transition_To_Non_zero Transition To Non-zero
Every Time -- write output every time record is processed.On Change -- write output every time VAL changes,
i.e.,
every time the result of the expression changes.When Zero -- when record is processed,
write output if VAL is zero.When Non-zero -- when record is processed,
write output if VAL is non-zero.Transition To Zero -- when record is processed,
write output only if VAL is zero and the last value was non-zero.Transition To Non-zero -- when record is processed,
write output only if VAL is non-zero and last value was zero.The DOPT field determines what data is written to the output link when the output is executed. The field is a menu field with two options:
Index Identifier Choice String 0 calcoutDOPT_Use_VAL Use CALC 1 calcoutDOPT_Use_OVAL Use OCAL
If Use CALC is specified,
when the record writes its output it will write the result of the expression in the CALC field,
that is,
it will write the value of the VAL field.
If Use OCAL is specified,
the record will instead write the result of the expression in the OCAL field,
which is contained in the OVAL field.
The OCAL field is exactly like the CALC field and has the same functionality it can contain the string representation of an expression which is evaluated at run-time.
Thus,
if necessary,
the record can use the result of the CALC expression to determine if data should be written and can use the result of the OCAL expression as the data to write.
If the OEVT field specifies a non-zero integer and the condition in the OOPT field is met, the record will post a corresponding event. If the ODLY field is non-zero, the record pauses for the specified number of seconds before executing the OUT link or posting the output event. During this waiting period the record is "active" and will not be processed again until the wait is over. The field DLYA is equal to 1 during the delay period. The resolution of the delay entry system dependent.
The IVOA field specifies what action to take with the OUT link if the Calcout record enters an INVALID alarm status.
The options are Continue normally,
Don't drive outputs,
and Set output to IVOV.
If the IVOA field is Set output to IVOV,
the data entered into the IVOV field is written to the OUT link if the record alarm severity is INVALID.
Field Summary Type DCT Default Read Write CA PP OUT Output Specification OUTLINK Yes Yes Yes No OOPT Output Execute Opt MENU (calcoutOOPT) Yes Yes Yes No DOPT Output Data Opt MENU (calcoutDOPT) Yes Yes Yes No OCAL Output Calculation STRING [80] Yes Yes Yes Yes OVAL Output Value DOUBLE No Yes Yes No OEVT Event To Issue STRING [40] Yes Yes Yes No ODLY Output Execute Delay DOUBLE Yes Yes Yes No IVOA INVALID output action MENU (menuIvoa) Yes Yes Yes No IVOV INVALID output value DOUBLE Yes Yes Yes No
These parameters are used to present meaningful data to the operator. Some are also meant to represent the status of the record at run-time.
The EGU field contains a string of up to 16 characters which is supplied by the user and which describes the values being operated upon.
The string is retrieved whenever the routine get_units() is called.
The EGU string is solely for an operator's sake and does not have to be used.
The HOPR and LOPR fields on;y refer to the limits if the VAL, HIHI, HIGH, LOW, and LOLO fields. PREC controls the precision of the VAL field.
The INAV-INLV fields indicate the status of the link to the PVs specified in the INPA-INPL fields, respectfully. These field can have four possible values:
Index Identifier Choice String 0 calcoutINAV_EXT_NC Ext PV NC 1 calcoutINAV_EXT Ext PV OK 2 calcoutINAV_LOC Local PV 3 calcoutINAV_CON Constant
Ext PV NC -- the PV wasn't found on this IOC and a Channel Access link hasn't been established.Ext PV OK -- the PV wasn't found on this IOC and a Channel Access link has been established.Local PV -- the PV was found on this IOC.Constant -- the corresponding link field is a constant.The OUTV field indicates the status of the OUT link. If has the same possible values as the INAV-INLV fields.
The CLCV and OLCV fields indicate the validity of the expression in the CALC and OCAL fields respectfully. If the expression in invalid, the field is set to one.
The DLYA field is set to one during the delay specified in ODLY.
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 EGU Engineering Units STRING [16] Yes Yes Yes No PREC Display Precision SHORT Yes Yes Yes No HOPR High Operating Rng DOUBLE Yes Yes Yes No LOPR Low Operating Range DOUBLE Yes Yes Yes No INAV INPA PV Status MENU (calcoutINAV) No 1 Yes No No INBV INPB PV Status MENU (calcoutINAV) No 1 Yes No No INCV INPC PV Status MENU (calcoutINAV) No 1 Yes No No INDV INPD PV Status MENU (calcoutINAV) No 1 Yes No No INEV INPE PV Status MENU (calcoutINAV) No 1 Yes No No INFV INPF PV Status MENU (calcoutINAV) No 1 Yes No No INGV INPG PV Status MENU (calcoutINAV) No 1 Yes No No INHV INPH PV Status MENU (calcoutINAV) No 1 Yes No No INIV INPI PV Status MENU (calcoutINAV) No 1 Yes No No INJV INPJ PV Status MENU (calcoutINAV) No 1 Yes No No INKV INPK PV Status MENU (calcoutINAV) No 1 Yes No No INLV INPL PV Status MENU (calcoutINAV) No 1 Yes No No OUTV OUT PV Status MENU (calcoutINAV) No Yes No No CLCV CALC Valid LONG No Yes Yes No OCLV OCAL Valid LONG No Yes Yes No DLYA Output Delay Active USHORT No Yes No No NAME Record Name STRING [61] No Yes No No DESC Descriptor STRING [41] Yes Yes Yes No
The possible alarm conditions for the Calcout record are the SCAN, READ, Calculation, and limit alarms. The SCAN and READ alarms are called by the record support routines. The Calculation alarm is called by the record processing routine when the CALC expression is an invalid one, upon which an error message is generated.
The following alarm parameters, which are configured by the user, define the limit alarms for the VAL field and the severity corresponding to those conditions.
The HYST field defines an alarm deadband for each limit.
See "Alarm Specification" for a complete explanation of alarms and these 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 HIHI Hihi Alarm Limit DOUBLE Yes Yes Yes Yes HIGH High Alarm Limit DOUBLE Yes Yes Yes Yes LOW Low Alarm Limit DOUBLE Yes Yes Yes Yes LOLO Lolo Alarm Limit DOUBLE Yes Yes Yes Yes HHSV Hihi Severity MENU (menuAlarmSevr) Yes Yes Yes Yes HSV High Severity MENU (menuAlarmSevr) Yes Yes Yes Yes LSV Low Severity MENU (menuAlarmSevr) Yes Yes Yes Yes LLSV Lolo Severity MENU (menuAlarmSevr) Yes Yes Yes Yes HYST Alarm Deadband DOUBLE Yes Yes Yes No
These parameters are used to determine when to send monitors for the value fields. These monitors are sent when the value field exceeds the last monitored field by the appropriate deadband, the ADEL for archiver monitors and the MDEL field for all other types of monitors. If these fields have a value of zero, every time the value changes, monitors are triggered; if they have a value of -1, every time the record is scanned, monitors are triggered. See "Monitor Specification" for a complete explanation of monitors.
Field Summary Type DCT Default Read Write CA PP ADEL Archive Deadband DOUBLE Yes Yes Yes No MDEL Monitor Deadband DOUBLE Yes Yes Yes No
These fields are not configurable using a configuration tool and none are modifiable at run-time. They are used to process the record.
The LALM field is used to implement the hysteresis factor for the alarm limits.
The LA-LL fields are used to decide when to trigger monitors for the corresponding fields. For instance, if LA does not equal the value for A, monitors for A are triggered. The MLST and ALST fields are used in the same manner for the VAL field.
Field Summary Type DCT Default Read Write CA PP LALM Last Value Alarmed DOUBLE No Yes No No ALST Last Value Archived DOUBLE No Yes No No MLST Last Val Monitored DOUBLE No Yes No No LA Prev Value of A DOUBLE No Yes No No LB Prev Value of B DOUBLE No Yes No No LC Prev Value of C DOUBLE No Yes No No LD Prev Value of D DOUBLE No Yes No No LE Prev Value of E DOUBLE No Yes No No LF Prev Value of F DOUBLE No Yes No No LG Prev Value of G DOUBLE No Yes No No LH Prev Value of H DOUBLE No Yes No No LI Prev Value of I DOUBLE No Yes No No LJ Prev Value of J DOUBLE No Yes No No LK Prev Value of K DOUBLE No Yes No No LL Prev Value of L DOUBLE No Yes No No
init_recordFor each constant input link, the corresponding value field is initialized with the constant value if the input link is CONSTANT or a channel access link is created if the input link is PV_LINK.
A routine postfix is called to convert the infix expression in CALC and OCAL to Reverse Polish Notation. The result is stored in RPCL and ORPC, respectively.
processSee next section.
specialThis is called id CALC or OCAL is changed.
special calls postfix.
get_unitsRetrieves EGU.
get_precisionRetrieves PREC.
get_graphic_doubleSets the upper display and lower display limits for a field. If the field is VAL, HIHI, HIGH, LOW, or LOLO, 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.
get_control_doubleSets the upper control and lower control limits for a field. If the VAL, HIHI, HIGH, LOW, or LOLO, 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 will be used.
get_alarm_doubleSets the following values:
upper_alarm_limit = HIHI
upper_warning_limit = HIGH
lower warning_limit = LOW
lower_alarm_limit = LOLO
process()The process() routine implements the following algorithm:
calcPerform(),
which calculates VAL from the prefix version of the expression given in CALC.
If calcPerform() returns success,
UDF is set to FALSE.execOutput() routine below.execOutput()calcPerform() for the postfix version of the expression in OCAL.
Otherwise,
use VAL.