The calculation or "Calc" record is used to perform algebraic, relational, and logical operations on values retrieved from other records. The result of its operations can then be accessed by another record so that it can then be used.
The record-specific fields are described below, grouped by functionality.
The Calc 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 Calc record consist of 12 input links INPA,
The fields can be database links,
channel access links,
If they are links,
they must specify another record's field or a channel access link.
If they are constants,
they will be initialized with the value they are configured with and can be changed via
They cannot be hardware addresses.
See "Address Specification" for information on how to specify database links.
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
At the core of the Calc record lies the CALC and RPCL fields. The CALC field contains the infix expresion which the record routine will use when it processes the record. The resulting value is placed in the VAL field and can be accessed from there. The CALC expression is actually converted to opcode and stored as 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 changed at run-time, and a special record routine calls 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 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 operators, the assignment operator, parentheses and commas, and the question mark or '?:' operator.
Field Summary Type DCT Default Read Write CA PP CALC Calculation STRING  Yes Yes Yes Yes RPCL Reverse Polish Calc NOACCESS No No No No
The expression uses 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 simply referenced by the field letter. For instance, the value obtained from INPA link is stored in the field A, and the value obtained from INPB is stored in field B. The field names can be included in the expression which will operate on their respective values, as in A+B. Also, the RNDM nullary function can be included as an operand in the expression in order to generate a random number between 0 and 1.
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 VAL field (which can be written to by a 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:
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
(A + B) < (C + D)
F + L + 10if
(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) ?
From 3.14.9 onwards,
this expresion must be written as
(A + B) < (C + D) ?
E : VAL
A & B
These parameters are used to present meaningful data to the operator. These fields are used to display VAL and other parameters of the calculation record either textually or graphically.
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 only refer to the limits of the VAL, HIHI, HIGH, LOW and LOLO fields. PREC controls the precision of the VAL field.
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  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 NAME Record Name STRING  No Yes No No DESC Descriptor STRING  Yes Yes Yes No
The possible alarm conditions for the Calc 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 of 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 paramaeters 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, everytime the value changes, monitors are triggered; if they have a value of -1, everytime 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 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
For 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 a PV_LINK.
A routine postfix is called to convert the infix expression in CALC to Reverse Polish Notation. The result is stored in RPCL.
See next section.
This is called if CALC is changed.
special calls postfix.
Sets 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 will be used.
Sets the upper control and the lower control 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.
Sets the following values:
upper_alarm_limit = HIHI
upper_warning_limit = HIGH
lower_warning_limit = LOW
lower_alarm_limit = LOLO
Routine process implements the following algorithm:
calcPerform, which calculates VAL from the postfix version of the expression given in CALC. If
calcPerformreturns success UDF is set to FALSE.