Calculation Output Record (calcout)
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.
Parameter Fields
The recordspecific fields are described below, grouped by functionality.
Scan Parameters
The Calcout record has the standard fields for specifying under what circumstances the record will be processed. These fields are listed in Scan Fields.
Read Parameters
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 
Expression
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 runtime than an infix expression. CALC can be changes at runtime, 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 semicolon 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 
Literals
Standard double precision floating point numbers
Inf: Infinity
Nan: Not a Number
Constants
PI: returns the mathematical constant π
D2R: evaluates to π/180 which, when used as a multiplier, converts an angle from degrees to radians
R2D: evaluates to 180/π which, when used as a multiplier, converts an angle from radians to degrees
Operands
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 AL 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).
Algebraic Operations
ABS: Absolute value (unary)
SQR: Square root (unary)
MIN: Minimum (any number of args)
MAX: Maximum (any number of args)
FINITE: returns nonzero if none of the arguments are NaN or Inf (any number of args)
ISNAN: returns nonzero if any of the arguments is NaN or Inf (any number of args)
CEIL: Ceiling (unary)
FLOOR: Floor (unary)
FMOD: Floating point modulo (binary) Added in 7.0.8
LOG: Log base 10 (unary)
LOGE: Natural log (unary)
LN: Natural log (unary)
EXP: Exponential function (unary)
^ : Exponential (binary)
** : Exponential (binary)
: Addition (binary)
: Subtraction (binary)
* : Multiplication (binary)
/ : Division (binary)
NOT: Negate (unary)
Trigonometric Operators
SIN: Sine
SINH: Hyperbolic sine
ASIN: Arc sine
COS: Cosine
COSH: Hyperbolic cosine
ACOS: Arc cosine
TAN: Tangent
TANH: Hyperbolic tangent
ATAN: Arc tangent
Relational Operators
>=
: Greater than or equal to>
: Greater than<=
: Less than or equal to<
: Less than#
: Not equal to=
: Equal to
Logical Operators
&& : And
 : Or
! : Not
Bitwise Operators

: Bitwise Or&
: Bitwise AndOR : Bitwise Or
AND : Bitwise And
XOR : Bitwise Exclusive Or
~
: One’s Complement<<
: Arithmetic Left Shift>>
: Arithmetic Right Shift>>>
: Logical Right Shift
Assignment Operator
:=
: assigns a value (right hand side) to a variable (i.e. field)
Parentheses, Comma, and Semicolon
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.
Conditional Expression
The C language’s question mark operator is supported. The format is:
condition ? True result : False result
Expression Examples
Algebraic
A + B + 10
Result is
A + B + 10
Relational
(A + B) < (C + D)
Result is 1 if
(A + B) < (C + D)
Result is 0 if
(A + B) >= (C + D)
Question Mark
(A + B) < (C + D) ? E : F + L + 10
Result is
E
if(A + B) < (C + D)
Result is
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
Result is E if (A + B)<(C + D)
Result is unchanged if (A + B)>=(C + D)
From 3.14.9 onwards, this expression must be written as
`(A + B) < (C + D) ? E : VAL`
Logical
A & B
Causes the following to occur:
Convert A to integer
Convert B to integer
Bitwise And A and B
Convert result to floating point
Assignment
sin(a); a:=a+D2R
Causes the Calc record to output the successive values of a sine curve in 1 degree intervals.
Output Parameters
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.
Operator Display Parameter
These parameters are used to present meaningful data to the operator. Some are also meant to represent the status of the record at runtime.
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.
Alarm Parameters
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 record alarms and of the standard 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 
Monitor Parameters
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 
Runtime Parameters
These fields are not configurable using a configuration tool and none are modifiable at runtime. They are used to process the record.
The LALM field is used to implement the hysteresis factor for the alarm limits.
The LALL 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 
Record Support
Record Support Routines
init_record
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 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.
process
See next section.
special
This is called if CALC or OCAL is changed. special
calls postfix.
get_units
Retrieves EGU.
get_precision
Retrieves PREC.
get_graphic_double
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 type will be used.
get_control_double
Sets 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_double
Sets the following values:
upper_alarm_limit = HIHI
upper_warning_limit = HIGH
lower warning_limit = LOW
lower_alarm_limit = LOLO
Record Processing
process()
The process()
routine implements the following algorithm:
Fetch all arguments.
Call routine calcPerform()
, which calculates VAL from the prefix version
of the expression given in CALC. If calcPerform()
returns success, UDF
is set to FALSE.
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. If also honors the alarm hysteresis factor (HYST). Thus the value must change by at least HYST before the alarm status and severity changes.
Determine if the Output Execution Option (OOPT) is met. If met, either
execute the output link (and output event) immediately (if ODLY = 0), or
schedule a callback after the specified interval. See the explanation for
the execOutput()
routine below.
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 ADEL and MDEL conditions are met.  Monitors for AL are checked whenever other monitors are invoked.  NSEV and NSTA are reset to 0
If no output delay was specified, scan forward link if necessary, set PACT FALSE, and return.
execOutput()
If DOPT field specifies the use of OCAL, call the routine calcPerform()
for the postfix version of the expression in OCAL. Otherwise, use VAL.
If the Alarm Severity is INVALID, follow the option as designated by the field IVOA.
The Alarm Severity is not INVALID or IVOA specifies “Continue Normally”, put the value of OVAL to the OUT link and post the event in OEVT (if nonzero).
If an output delay was implemented, process the forward link.