RRM 3-13 String Calcout

sCalcout Record

This page actually describes the EPICS-3.14-compatible version of the sCalcout record. Text that does not apply to the 3.13-compatible version is rendered in blue. Documentation specific to the 3.13-compatible version is currently not available in this format, but may be found in the 'std' module of a 3.13-compatible synApps package.

The String Calculation Output or "sCalcout" record is derived from the Calcout record and extends it by supporting string expressions and operands. The record has 12 numeric fields (A...L) and 12 string fields (AA...LL), which are used as input variables for the expression. It calls an extended version of the EPICS calculation engine that accepts string arguments, supports a variety of string functions, and produces both numeric and string results, in the VAL and SVAL fields, respectively. The record's output link writes string or numeric data, depending on the data type of the field to which it is linked.

Parameter Fields

The fields in this record fall into the following categories:

• Scan Parameters
• Read Parameters
• Expression Parameters
• Output Parameters
• Operator Display Parameters
• Alarm Parameters
• Monitor Parameters
• Run-Time Parameters

Scan Parameters

The sCalcout record has the standard fields for specifying under what circumstances the record will be processed. These fields are listed in Scan Fields. In addition, Scanning Specification explains how these fields are used. Since the sCalcout record supports no direct interfaces to input hardware that might generate an interrupt, it cannot be scanned on I/O interrupt, so its SCAN field cannot be I/O Intr.

Read Parameters

The read parameters for the sCalcout record consist of 24 input links: 12 for numeric values (INPA→A, INPB→B, ... INPL→L); and 12 for string values (INAA→AA, INBB→BB, ... INLL→LL). The fields can be database links, channel access links, or constants. If they are links, they must contain a PV name. If they are constants, associated value fields will be initialized with the constants. These fields cannot be hardware addresses. In addition, the sCalcout record contains the fields INAV, INBV, ... INLV, which indicate the status of the links to numeric fields, and the fields IAAV, IBBV, ... ILLV, which indicate the status of the links to string fields. These fields indicate whether or not the specified PV was found and a link to it established. See Operator Display Parameters for an explanation of these fields.

See Address Specification for information on how to specify database links.

Field	Summary	Type	DCT	Initial	Access	Modify	Rec Proc Monitor
INPA	Input Link A	INLINK	Yes	0	Yes	Yes	Yes
INPB	Input Link B	INLINK	Yes	0	Yes	Yes	Yes
...	...	...	...	...	...	...	...
INPL	Input Link L	INLINK	Yes	0	Yes	Yes	Yes
INAA	Input Link AA	INLINK	Yes	0	Yes	Yes	Yes
INBB	Input Link BB	INLINK	Yes	0	Yes	Yes	Yes
...	...	...	...	...	...	...	...
INLL	Input Link LL	INLINK	Yes	0	Yes	Yes	Yes

Expression Parameters

Field	Summary	Type	DCT	Initial	Access	Modify	Rec Proc Monitor	PP
CALC	Infix expression	String[40]	Yes	""	Yes	Yes	Yes	No
CLCV	CALC Valid	Long	No	0	Yes	No	Yes	No
OCAL	Infix expression	String[40]	Yes	""	Yes	Yes	Yes	No
OCLV	OCAL Valid	Long	No	0	Yes	No	Yes	No

Like the Calcout record, the sCalcout record has the fields CALC and OCAL, in which the developer or user can enter an infix expression to be evaluated when the record is processed. The numeric value resulting from evaluation of CALC will be placed in the VAL field, and the resulting string value will be placed in the SVAL field. VAL 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. Either VAL and SVAL can also be written to the output link. (If you elect to write an output value, the record will choose between VAL and SVAL, depending on the data type of the field at the other end of the output link.)

The CALC and OCAL expressions are actually converted to opcodes and stored in postfix notation in the RPCL and ORPC fields. It is these expressions which are actually used to calculate VAL. A postfix expression can be evaluated more efficiently at run-time than an infix expression would be. When CALC or OCAL is changed at run-time, the record-support routine special() will call a function to check it, and convert it to postfix.

In simple cases, OCAL is ignorable. It's use will be described later, in Output Parameters.

sCalcout-record expressions are very similar to standard EPICS Calc expressions, such as those used with the Calcout record. But in place of the standard EPICS calc engine (which does not support string fields or operations), sCalcout-record uses the sCalc engine, a separate piece of software, which normally is distributed with the sCalcout record. The differences between these engines that matter for numeric expressions are the following:

• The constants S2R (arc-seconds-to-radians) and R2S are supported.
• The functions MIN() and MAX() may have more than two arguments.
• The binary operators '>&' (larger of the operands) and '<&' (smaller) are supported.
• The binary operator '!=' (not equal) is a permitted alternatives '#'.
• The unary operator '@' selects an input field by number. (E.g., '@0' means 'A'. If 'B' has the value 3, '@b' means 'D'.)

Expressions supported by the sCalcout record can involve operands, algebraic operators and functions, trigonometric functions, relational operators, logical operators, string operators and functions, parentheses and commas, and the conditional '?:' operator. Numeric and string operands are supported, and any operand can be used with any operator or function. If an operand has the "wrong" type for the function or operator with which it is used, the operand will be converted implicitly to the correct type.

Grouping of operands with parentheses is important not only to specify the order in which operations are to be performed, but also to distinguish operands from operators whose names are spelled out, such as the logical operator 'AND'. For example, the expression 'AANDB', which could have meant 'A AND B', will be (mis)interpreted by the parser as 'AA NDB'.

Operands

The expression can use the values retrieved from the input links as operands, though constants can be used as operands too. These values retrieved from the input links are stored in the A-L, and AA-LL fields. The values to be used in the expression are simply referenced by the field name. For example, the value obtained from the 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.

Field	Summary	Type	DCT	Initial	Access	Modify	Rec Proc Monitor	PP
A	Input Value A	DOUBLE	No	0	Yes	Yes/No*	Yes	Yes
B	Input Value B	DOUBLE	No	0	Yes	Yes/No*	Yes	Yes
...	...	...	...	...	...	...	...	...
L	Input Value L	DOUBLE	No	0	Yes	Yes/No*	Yes	Yes
AA	Input string AA	STRING (40)	No	0	Yes	Yes/No*	Yes	Yes
BB	Input string BB	STRING (40)	No	0	Yes	Yes/No*	Yes	Yes
...	...	...	...	...	...	...	...	...
LL	Input string LL	STRING (40)	No	0	Yes	Yes/No*	Yes	Yes

Legend: * If a non-blank input link is associated with this field, then it may not be modified. This is true even if the input link is invalid (in which case, the value will be 0, for a numeric field, or "Huh?", for a string field).

There are a few special operands not associated with input fields, but defined by the record (more exactly, defined by the calc engine the record uses to evaluate expressions). All but RNDM are constants.

PI	3.141592654
D2R	Degrees to radians (PI/180)
R2D	Radians to degrees (1/D2R)
S2R	Arc seconds to radians (D2R/3600)
R2S	Radians to arc seconds (1/S2R)
RNDM	Random number between 0 and 1.

Algebraic Functions/Operators

Op	Description	Example
ABS	Absolute value (one-argument function)	ABS(A)
SQRT	Square root (one-argument function) (SQR is deprecated)	SQRT(A)
MIN	Minimum (two-or-more-argument function)	MIN(A,B)
MAX	Maximum (two-or-more-argument function)	MAX(A,B)
CEIL	Ceiling (one-argument function)	CEIL(A)
FLOOR	Floor (one-argument function)	FLOOR(A)
INT	Nearest integer (one-argument function)	INT(A)
NINT	Nearest integer (one-argument function)	NINT(A)
LOG	Log base 10 (one-argument function)	LOG(A)
LN	Natural logarithm (one-argument function)	LN(A)
LOGE	Deprecated synonym for 'LN'	LOGE(A)
EXP	Exponential function (unary)	EXP(A)
^	Exponential (binary) (Same as '**'.)	A^B
**	Exponential (binary) (Same as '^'.)	A**B
+	Addition (binary)	A+B
-	Subtraction (binary)	A-B
*	Multiplication (binary)	A*B
/	Division (binary)	A/B
%	Modulo (binary)	A%B
-	Negate (unary)	-A
NOT	Negate (unary)	NOT A
>&	Max (binary)	A>?B
<&	Min (binary)	A<?B

Trigonometric Functions

Op	Description	Example
SIN	Sine (one-argument function)	SIN(A)
SINH	Hyperbolic sine (one-argument function)	SINH(A)
ASIN	Arc sine (one-argument function)	ASIN(A)
COS	Cosine (one-argument function)	COS(A)
COSH	Hyperbolic cosine (one-argument function)	COSH(A)
ACOS	Arc cosine (one-argument function)	ACOS(A)
TAN	Tangent (one-argument function)	TAN(A)
TANH	Hyperbolic tangent (one-argument function)	TANH(A)
ATAN	Arc tangent (one-argument function)	ATAN(A)
ATAN2	Alternate form of arctangent (two-argument function)	ATAN2(A,B)

Relational Operators

Op	Description	Example
>=	Greater than or equal to	A>=B
>	Greater than	A>B
<=	Less than or equal to	A<=B
<	Less than	A<B
!=	Not equal to (same as '#')	A!=B
#	Not equal to (same as '!=')	A#B
==	Equal to (same as '=')	A==B
=	Equal to (same as '==')	A=B

Logical Operators

Op	Description	Example
&&	Logical AND	A&&B
||	Logical OR	A||B
!	Logical NOT	!A

Bitwise Operators

Op	Description	Example
|	Bitwise OR	A|B
OR	Bitwise OR	A OR B
&	Bitwise AND	A&B
AND	Bitwise AND	A AND B
XOR	Bitwise Exclusive OR	A XOR B
~	One's Complement	~A
<<	Left shift	A<<B
>>	Right shift	A>>B

Parentheses and Comma

The open and close parentheses are supported. Nested parenthesis are supported.

The comma is supported when used to separate the arguments of a binary function.

Conditional Expression

The C language's question mark operator is supported. The format is:

 <expression> ? <expression-true result> : <expression-false  result>

String Functions/Operators

Most two-argument string functions and binary string operators are "overloaded" numeric functions and operators that perform string operations only if both of their arguments/operands are strings.

Op	Description	Example
MIN	Minimum lexically (two-or-more-argument function)	MIN('a','b') → 'a'
MAX	Maximum lexically (two-or-more-argument function)	MAX('a','b') → 'b'
INT	Find first number in string; return nearest integer (one-argument function)	INT('1.9') → 1 INT('abc1.9') → 1
NINT	Find first number in string; return nearest integer (one-argument function)	NINT('1.9') → 2 NINT('abc1.9') → 2
+	Concatenate (binary)	'a'+'b' → 'ab'
-	Delete first occurrence of substring (binary)	'abca'-'a' → 'bca'
-|	Delete first occurrence of substring (binary)	'abca'-'a' → 'bca'
|-	Delete last occurrence of substring (binary)	'abca'-'a' → 'abc'
>=	Lexically greater than or equal (binary)	'a'>='b' → 0
>	Lexically greater than (binary)	'a'>'b' → 0
<=	Lexically less than or equal (binary)	'a'<='b' → 1
<	Lexically less than (binary)	'a'<'b' → 1
!=	Lexically not equal to (binary)	'a'!='b' → 1
==	Lexically equal to (binary)	'a'=='b' → 0
DBL	Convert argument to double (one-argument function)	DBL('1') → 1.0 DBL('abc1.23') → 1.23
STR	Convert argument to string (one-argument function)	STR(1) → '1.00000000'
BYTE	Convert first character of string argument to double (one-argument function)	BYTE('abc') → 97.0
PRINTF	Return string constructed from format string and string or double argument (two-argument function)  (NOTE: '$P' is a synonym for PRINTF) Allowed format indicators: %cdeEfgGiosuxX Disallowed indicators: *	PRINTF("%.2f",1.23) → '1.23'
SSCANF	Return string or double parsed from string argument according to format string (two-argument function) (NOTE: '$S' is a synonym for SSCANF) Allowed format indicators: %*[cdeEfgGhilosuxX Disallowed indicators: $npw	SSCANF('V=1.25', "%*2c%lf") → 1.25
TR_ESC	Translate escape sequences into the characters they represent (one-argument function). (NOTE: '$T' is a synonym for TR_ESC.) TR_ESC() applies dbTranslateEscape() to its argument. This function is approximately the opposite of ESC(). An escaped null character will terminate the result string	TR_ESC("a\x62c") → 'abc'
ESC	Translate escape characters into equivalent escape sequences. (one-argument function) (NOTE: '$E' is a synonym for ESC) ESC() applies epicsStrSnEscaped() to its argument. This function is approximately the opposite of TR_ESC(). The first null character found in the input string terminates it. If there is no null chaacter, the string is assumed to be 40 characters long.	ESC("a<return>c") → 'a\rc'
[	Substring	'abcdef'[1,3] → 'bcd' 'abcdef'['ab','ef'] → 'cd' 'abcdef'[0,-1] → 'abcdef'
{	Substring substitution	'abcdef'{'cd','XX'} → 'abXXef'
"	String indicator	"abc"
'	String indicator	'abc'

Operand-Array Operators

Op	Description	Example
@	Numeric array element. Regard the numeric fields A-L as an array whose elements are numbered 0-11, and return the element whose number follows. (unary)	@A
@@	String array element. Regard the string fields AA-LL as an array of strings whose elements are numbered 0-11, and return the element whose number follows. (unary)	@@A

Examples

Algebraic Examples

A + B + 10 Result is A + B + 10

Relational Examples

(A + B) < (C + D) Result is 1 if (A+B) < (C+D) Result is 0 if (A+B) >= (C+D)

Question Mark Examples

(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)

(A+B)<(C+D)?E Result is E if (A+B) < (C+D) Result is unchanged if (A+B) >= (C+D)

Logical Examples

A&B Causes the following to occur:

• Convert A to integer
• Convert B to integer
• Perform bit-wise AND of A and B
• Convert result to floating point

String Examples

A + "abc"
A + "abc1.2"
A + AA (where AA = "abc1.2")

Result is A. The strings "abc" and "abc1.2" will be converted implicitly to the number 0.

A + DBL("abc1.2")

Result is A + 1.2. Explicit conversion to a number (by DBL, INT, or NINT) is more aggressive than implicit conversion, and skips leading non-numeric characters.

"abc" + "def"

Result is "abcdef".

PRINTF("abc%1.2f", A) (where A = 1.2345)

Result is "abc1.23".

NOTE: unlike the c-language function printf(<format>,<arg1>,<arg2>,...), this function accepts only one argument after the format string.

SSCANF(AA, "%*3c%lf") (where AA = "abc1.2")

Result is "1.20000000". (The format fragment "%*3c" directs sscanf to ignore three characters.)

NOTE: unlike the c-language function sscanf(<source>,<format>,<dest1>,<dest2>,...), this function cannot store to a variable, but only to the value stack.

BYTE("ABC")

Result is 65, the ASCII code for "A" in decimal.

"abcdef"[2,4]

Result is "cde". (The first character of the string is numbered "0".)

"abcdef"[-2,-1]

Result is "ef". (The last character of the string is numbered "-1".)

"abcdef"["ab","ef"]

Result is "cd". (If the first argument is a string, it returns the index of the first character after a successful match, or the first character in the string if no match was found. If the second argument is a string, it returns the index of the last character before a successful match, or the last character in the string if no match was found.) In other words, string arguments delimit the substring they are specifying without participating in it.)

A==2 ? "yes" : "no"

Result is "yes" if A == 2; otherwise, result is "no".

"abcdef"{"bcd","dcb"}

Result is "adcbef".

"abcdef"{"zzz","dcb"}

Result is "abcdef". (If no match, then no replacement.)

"abcdef"[1,-2][1,-2]

Result is "cd"

Array Examples

@0

Result is the value of the numeric variable A. ("@0" is just another name for A.)

@@0

Result is the value of the string variable AA.

@(A+B)

Result is the value of the numeric variable whose number is given by the sum of A and B.

Output Parameters

These parameters specify and control the output capabilities of the sCalcout 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:

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 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.
Never	Don't write output ever.

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: Use CALC or Use OCAL. If Use CALC is specified, when the record writes its output it will write the result of the expression in the CALC record, that is, it will write the value of the VAL [SVAL] field to a double [string] destination. 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 (string result in the OSV) 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 is 1/60 of a second (it uses the VxWorks tickLib).

The IVOA field specifies what action to take with the OUT link if the sCalcout 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	Initial	Access	Modify	Rec Proc Monitor	PP
OUT	Output Specification	OUTLINK	Yes	0	Yes	Yes	N/A	No
OOPT	Output Execute Option	Menu	Yes	0	Yes	Yes	No	No
DOPT	Output Data Option	Menu	Yes	0	Yes	Yes	No	No
OCAL	Output Calculation	STRING[36]	Yes	Null	Yes	Yes	No	No
OVAL	Output Value	DOUBLE	No	0	Yes	Yes	Yes	No
OEVT	Event To Issue	SHORT	Yes	0	Yes	Yes	No	No
ODLY	Output Execution Delay	FLOAT	Yes	0	Yes	Yes	No	No
IVOV	Invalid Output Action	Menu	Yes	0	Yes	Yes	No	No
IVOA	Invalid Output Value	DOUBLE	Yes	0	Yes	Yes	No	No
OSV	Output string value	STRING[40]	NO	0	Yes	Yes	Yes	No
WAIT	Wait for completion?	Menu	Yes	"NoWait"	Yes	Yes	Yes	No

The sCalcout record now uses device support to write to the OUT link. Soft device supplied with the record is selected with

the .dbd specification

 field(DTYP,"Soft Channel") 

This device support uses the record's WAIT field to determine whether to wait for completion of processing initiated by the OUT link before causing the record to execute its forward link. The mechanism by which this waiting for completion is performed requires that the OUT link have the attribute CA -- i.e., the link text looks something like

xxx:record.field CA NMS

Currently, the record does not try to ensure that WAIT and OUT are compatibly configured. If WAIT == "Wait", but the link looks like

xxx:record.field PP NMS

for example, then the record will not wait for completion before executing its forward link.

Operator Display Parameters

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. An example of an interactive MEDM display screen that displays the status of the sCalcout record is located here.

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.

The INAV-INLV and IAAV-ILLV fields indicate the status of the link to the PVs specified in the INPA-INPL and INAA-INLL fields, respectively. The fields can have three possible values:

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. It 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, respectively. If the expression is invalid, the field is set to one.

The DLYA field is set to one during the delay interval specified in ODLY.

Field	Summary	Type	DCT	Initial	Access	Modify	Rec Proc Monitor	PP
EGU	Engineering Units	STRING [16]	Yes	Null	Yes	Yes	No	No
PREC	Display Precision	SHORT	Yes	0	Yes	Yes	No	No
HOPR	High Operating Range	FLOAT	Yes	0	Yes	Yes	No	No
LOPR	Low Operating Range	FLOAT	Yes	0	Yes	Yes	No	No
INAV	Link Status of INPA	Menu	No	1	Yes	No	No	No
INBV	Link Status of INPB	Menu	No	1	Yes	No	No	No
...	...	...	...	...	...	...	...	...
INLV	Link Status of INPL	Menu	No	1	Yes	No	No	No
OUTV	OUT PV Status	Menu	No	0	Yes	No	No	No
CLCV	CALC Valid	LONG	No	0	Yes	Yes	No	No
OCLV	OCAL Valid	LONG	No	0	Yes	Yes	No	No
DLYA	Output Delay Active	USHORT	No	0	Yes	No	No	No
NAME	Record Name	STRING [29]	Yes	0	Yes	No	No	No
DESC	Description	STRING [29]	Yes	Null	Yes	Yes	No	No
IAAV	Link Status of INAA	Menu	No	1	Yes	No	No	No
IBBV	Link Status of INBB	Menu	No	1	Yes	No	No	No
...	...	...	...	...	...	...	...	...
ILLV	Link Status of INLL	Menu	No	1	Yes	No	No	No

Alarm Parameters

The possible alarm conditions for the sCalcout 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 the EPICS Record Reference Manual for a complete explanation of alarms and these fields.

Field	Summary	Type	DCT	Initial	Access	Modify	Rec Proc Monitor	PP
HIHI	Hihi Alarm Limit	FLOAT	Yes	0	Yes	Yes	No	Yes
HIGH	High Alarm Limit	FLOAT	Yes	0	Yes	Yes	No	Yes
LOW	Low Alarm Limit	FLOAT	Yes	0	Yes	Yes	No	Yes
LOLO	Lolo Alarm Limit	FLOAT	Yes	0	Yes	Yes	No	Yes
HHSV	Severity for a Hihi Alarm	Menu	Yes	0	Yes	Yes	No	Yes
HSV	Severity for a High Alarm	Menu	Yes	0	Yes	Yes	No	Yes
LSV	Severity for a Low Alarm	Menu	Yes	0	Yes	Yes	No	Yes
LLSV	Severity for a Lolo Alarm	Menu	Yes	0	Yes	Yes	No	Yes
HYST	Alarm Deadband	DOUBLE	Yes	0	Yes	Yes	No	No

Monitor Parameters

These parameters are used to determine when to send monitors for the value fields. The 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.

Field	Summary	Type	DCT	Initial	Access	Modify	Rec Proc Monitor	PP
ADEL	Archive Deadband	DOUBLE	Yes	0	Yes	Yes	No	No
MDEL	Monitor, i.e. value change, Deadband	DOUBLE	Yes	0	Yes	Yes	No	No

Run-time Parameters

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 MLST fields are used in the same manner for the VAL field.

Field	Summary	Type	DCT	Initial	Access	Modify	Rec Proc Monitor	PP
LALM	Last Alarmed Value	DOUBLE	No	0	Yes	No	No	No
ALST	Archive Last Value	DOUBLE	No	0	Yes	No	No	No
MLST	Monitor Last Value	DOUBLE	No	0	Yes	No	No	No
LA	Previous Input Value for A	DOUBLE	No	0	Yes	No	No	No
LB	Previous Input Value for B	DOUBLE	No	0	Yes	No	No	No
...	...	...	...	...	...	...	...	...
LL	Previous Input Value for A	DOUBLE	No	0	Yes	No	No	No
LAA	Previous Input Value for AA	STRING[40]	No	0	Yes	No	No	No
LBB	Previous Input Value for BB	STRING[40]	No	0	Yes	No	No	No
...	...	...	...	...	...	...	...	...
LLL	Previous Input Value for LL	STRING[40]	No	0	Yes	No	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 sCalcPostfix is called to convert the infix expression in CLCA-CLCV to postfix notation. The results are stored in RPCA-RPCP.

process

The process() routine implements the following algorithm:

1. Fetch values from all valid input links.
2. Call sCalcPerform(), which evaluates the expression specified in CALC and stores the result in VAL. If sCalcPerform() returns success, UDF is set to FALSE.
3. 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. It also honors the alarm hysteresis factor (HYST). Thus the value must change by at least HYST before the alarm status and severity changes.
4. Determine if the Output Execution Option (OOPT) is met. If it is met, either execute the output link (and output event) immediately (if ODLY=0), or schedule a callback to do so after the specified interval. See the explanation for the execOutput() routine below.
5. Determine what fields should be posted, and with what attributes.
   1. Post all fields the record has changed.
   2. Alarm monitors are invoked if the alarm status or severity has changed.
   3. Archive and value change monitors are invoked if ADEL and MDEL conditions are met.
   4. NSEV and NSTA are reset to 0
6. Call device support to execute output link.
7. If we're not waiting for the output delay to expire, or for a completion callback, process the forward link, set PACT FALSE, and return.

special

This is called if any of the fields A-L, CALC, OCAL, INPA-INPL, INAA-INLL, or OUT are changed. For expressions fields, special() calls sCalcPostfix. For value fields, special() keeps track of which fields have changed, because expressions will not be evaluated for fields that have been written to. For link fields, special() starts the process of checking link status.

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 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.

get_alarm_double

Sets the following values:

• upper_alarm_limit = HIHI
• upper_warning_limit = HIGH
• lower_warning_limit = LOW
• lower_alarm_limit = LOLO

execOutput()

1. If DOPT field specifies the use of OCAL, call the routine sCalcPerform for the postfix version of the expression in OCAL. Otherwise, use VAL.
2. If the Alarm Severity is INVALID, follow the option as designated by the field IVOA.
3. If the Alarm Severity is not INVALID or IVOA specifies "Continue Normally", call device support to write the value of OVAL to device or PV specified by the OUT link, and post the event in OEVT (if non-zero).

Availability

The sCalcout record is not included with EPICS base. The 3.14-compatible version is available as part of the calc module, which is part of the synApps package of EPICS-based synchrotron-beamline software. The 3.13-compatible version is available as part of the std module of a 3.13-compatible synApps distribution.

---

EPICS Record Reference Manual - 7 JUNE 2006