sCalcout - String Calculation Output Record

Contents

1. - Introduction
2. - Scan Parameters
3. - Read Parameters
4. - Expressions
4.1. - Operands
4.2. - Algebraic Functions/Operators
4.3. - Trigonometric Functions
4.4. - Relational Operators
4.5. - Logical Operators
4.6. - Bitwise Operators
4.7. - Special Characters
4.8. - Conditional Expression
4.9. - String Functions/Operators
4.10. - Array Operators
4.11. - Miscellaneous Operators
4.12. - Examples
Algebraic
Relational
Question Mark
Logical
String
Argument Array
Store
Loop
5. - Output Parameters
6. - Operator Display Parameters
7. - Alarm Parameters
8. - Monitor Parameters
9. - Run-time Parameters
10. - Record Support Routines
init_record
process
special
get_value
get_units
get_precision
get_graphic_double
get_control_double
get_alarm_double
11. - Record Processing
11.1. - process()
11.2. - execOutput()
12. - Sample Database

1. Introduction

The String Calculation Output or "sCalcout" record is derived from the Calcout record and extends it by supporting string expressions in addition to numeric expressions.  The record has 12 string fields (AA...LL) used as input variables for the expression; calls an extended version of the EPICS calculation engine that accepts string arguments, supports a variety of string functions, and can produce string results; and its output link writes string or numeric data depending on the data type of the field to which it is linked.

 


2. Scan Parameters

The sCalcout record has the standard fields for specifying under what circumstances the record will be processed. See the EPICS Record Reference Manual for these fields and their use.

 


3. Read Parameters

The read parameters for the sCalcout record consist of 24 input links: 12 to numeric fields (INPA -> A, INPB -> B, . . . INPL -> L); and 12 to string fields (INAA -> AA, INBB -> BB, ...INLL -> LL). 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 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 Section 6, Operator Display Parameters for an explanation of these fields.

From most types of PV's, the sCalcout record's string input links fetch data as strings, and depend on EPICS to convert a PV's native value to string. But when an sCalcout record's string input link names a PV whose data type is an array of DBF_CHAR or DBF_UCHAR, the record fetches up to 39 array elements from the array in their native form, translates the result using epicsStrSnPrintEscaped(), and truncates the result to fit into a 40-character string.

 See the EPICS Record Reference Manual 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 N/A
INPB Input Link B INLINK Yes 0 Yes Yes N/A
... ... ... ... ... ... ... ...
INPL Input Link L INLINK Yes 0 Yes Yes N/A
INAA Input Link AA INLINK Yes 0 Yes Yes N/A
INBB Input Link BB INLINK Yes 0 Yes Yes N/A
... ... ... ... ... ... ... ...
INLL Input Link LL INLINK Yes 0 Yes Yes N/A

 


4. Expressions

Like the Calc record, the sCalcout record has a CALC field into which you can enter an expression for the record to evaluate when it processes. The resulting numeric value 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 Section 5, 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 expression is actually converted to opcodes and stored in postfix notation in the RPCL field. It is this expression which is actually used to calculate VAL. The postfix expression is evaluated more efficiently at run-time than an infix expression would be. When CALC is changed at run-time, the record-support routine special() will call a function to check it, and convert it to postfix notation.
The record also has a second set of calculation-related fields described in Section 5, Output Parameters.
 
Field Summary Type DCT Initial Access Modify Rec Proc Monitor PP
CALC Calculation STRING[36] Yes 0 Yes Yes Yes No
VAL Value DOUBLE No 0 Yes Yes Yes No
RPCL Reverse Polish NOACCESS No 0 No No N/A No
SVAL String value STRING (40) No 0 Yes Yes Yes No

Expressions supported by the string calculation 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. The expression can consist of any of these operators, as well as any of the values from the input fields, which are the operands.

 Grouping of operands with parentheses is important not only to specify the order in which operations are to be done, but also to distinguish operands from operators whose names are spelled out, such as the logical operator 'AND'. The expression 'AANDB', which could have meant 'A AND B', will be misinterpreted by the parser, which will interpret 'AA' as the name of a string variable.

4.1. Operands

The expression can use as operands the values retrieved from the input links, and literal constants such as "abc", "1.5", and "23". (Numeric constants in expressions must be either floating-point numbers, or integers in base ten. Numbers like "0x03" will not be understood by the expression parser.) 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

* If a valid input link is associated with this field, then it may not be modified.

 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.

4.2. 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,C)
MAX Maximum (two-or-more-argument function) MAX(A,B,C)
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

4.3. 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)

4.4. 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

4.5. Logical Operators

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

4.6. 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

4.7. Special Characters

Parentheses, and nested parentheses are permitted (sometimes required) in expressions.

The comma is required to separate the arguments of a binary function.

Quotes of two kinds (" and ') are permitted to indicate the beginning and end of a string expression. The expression parser treats these quote characters in exactly the same way, so you can use pairs of either. Using one kind of quote allows you to include the other kind in a string. Note that string calc expressions defined in an EPICS database must use the ' character to delimit embedded strings, because database tools will use " to delimit the entire expression.

Escape sequences understood by the Epics routines dbTranslateEscape() and epicsStrSnEscaped() are permitted in strings handled by the sCalcout record, and the sCalc engine supplies functions that encode and decode escaped strings. Here's the current escape list:
\a \b \f \n \r \t \v \\ \? \' \" \000 \xhh

Note that '\000' represents an octal number, and may include one, two, or three octal digits. \xhh is a two-digit hexadecimal number.

See the Application Developer's Guide for more on this topic.

4.8. Conditional Expression

The C language's question mark operator is supported. The format is:
 <expression> ? <expression-true result> : <expression-false  result>

4.9. 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) MAX('a','b','c') -> 'a'
MAX Maximum lexically (two-or-more-argument function) MAX('a','b','c') -> 'c'
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
>> Right shift characters (fill behind with spaces). (binary) 'abc'>>2 -> ' abc'
<< Left shift characters. (binary) 'abc'<<2 -> 'c'
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: $npw
SSCANF('V=1.25', "%*2c%lf") -> 1.25
READ Read binary data. This function is similar in form to SSCANF, and is roughly analogous in function, but it operates on binary data. The first argument is the string from which data is to be copied. If this string contains any unprintable characters, they will have been converted to escape sequences by the software that transported them to this point. READ() converts this string to a raw binary array, using the EPICS function dbTranslateEscape(), copies bytes from that array into a temporary numeric variable, whose type depends on the format string, converts the result to double, and returns this value.
(NOTE: '$R' is a synonym for READ)

The format string is similar to that of the SSCANF function, but only the following subset of format indicators is supported:
formatresulting behavior
%i %dcopy four bytes to a long signed integer
%hi %hdcopy two bytes to a short signed integer
%o %u %x %Xcopy four bytes to a long unsigned integer
%ho %hu %hx %hXcopy two bytes to a short unsigned integer
%e %E %f %g %Gcopy four bytes to a float
%le %lE %lf %lg %lGcopy eight bytes to a double
%ccopy one byte to a signed character
%*suppress assignment to next conversion indicator. Only one '%*' is honored.
This is the only reliable way to skip past a specified number of bytes in a binary input string. For a non-escaped string, something like 'aa[3,5]' would have worked as well. But if the string aa might include escape sequences, character offsets in the escaped string will depend on the values of the characters, because printable characters are not escaped.

Allowed format indicators: %*cdeEfgGhilouxX
Disallowed indicators: $npw[s

READ('\x01\x02', "%hu") -> 258

READ('\x01\x02', "%*c%hu") -> 2
WRITE Write binary data. This function is similar in form to PRINTF, and is roughly analogous in function, but it operates on binary data. The first argument is the format string; the second is the data to be written. After the data have been written to a buffer, the buffer is processed by epicsStrSnEscaped() and returned.
(NOTE: '$W' is a synonym for WRITE)

The format string is similar to that of the PRINTF function, but only the following subset of format indicators is supported:
formatresulting behavior
%i %dconvert to a long signed integer and write four bytes
%hi %hdconvert to to a short signed integer and copy two bytes
%o %u %x %Xconvert to a long unsigned integer and copy four bytes
%ho %hu %hx %hXconvert to a short unsigned integer and copy two bytes
%e %E %f %g %Gconvert to a float and copy four bytes
%le %lE %lf %lg %lGconvert to a double and copy eight bytes
%cconvert to a signed character and copy one byte

Allowed format indicators: %cdeEfgGhilouxX
Disallowed indicators: $npw[s

WRITE('%hd', 1250) -> '\004\342'
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'
CRC16 Calculate Modbus/RTU 16-bit CRC and return it as an escaped string. CRC16('\x01\x03') -> '\x01\x03\x40\x21'
MODBUS Calculate Modbus/RTU 16-bit CRC and append it, as an escaped string, to the argument. CRC16('\x01\x03') -> '\x40\x21'
LRC Calculate Modbus/ASCII 8-bit LRC and return it as an escaped string. LRC('\x01\x03') -> '\xfc'
AMODBUS Calculate Modbus/ASCII 8-bit LRC and append it, as an escaped string, to the argument. Note that this doesn't do everything needed for an actual device. The string is supposed to be converted to binary, have its LRC appended, and ':' prepended. Then the whole thing then gets converted to ASCII characters. AMODBUS('\x01\x03') -> '\x01\x03\xfc'
XOR8 Calculate 8-bit XOR checksum and return it as an escaped string. XOR8('\x01\x03') -> '\x02'
ADD_XOR8 Calculate 8-bit XOR checksum and append it, as an escaped string, to the argument. ADD_XOR8('\x01\x03') -> '\x01\x03\x02'
LEN Return length of string argument. If arg is not a string, it will be converted to string. LEN('abc') -> 3
[ 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'
Functions and operators rendered in this color are experimental. The names or implementations may change in a future version of this software.

4.10. 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

4.11. Miscellaneous Operators

Op Description Examples
:= Store value of right hand side in location specified by left hand side. (binary) A:=1.2
@7:='abc'

AA:='abc'

@@4:='abc'
UNTIL Execute expression until its value is TRUE. (binary)
The total number of iterations is limited to the ioc-shell variable sCalcLoopMax, which defaults to 1000.
until(1)
until(a:=a+1;b:=b-1;b<1)

4.12. 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)

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

Logical

A&B
Causes the following to occur:
  1. Convert A to integer
  2. Convert B to integer
  3. Perform bit-wise AND of A and B
  4. Convert result to floating point

String

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.)

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"

Argument array

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

@@0
Result in the value of the string variable AA.

@(A+B)
Result in the value of the numeric variable whose number is given by the sum of A and B.


Store

The "Store" operator is the only string-calc operator that does not produce a value. Thus, the expression a:=0 is an incomplete and therefore illegal calc expression, because it leaves us with nothing to write to the record's VAL field.
A:=A-1;7
Evaluate the expression A-1, store the result in the input variable A, and set the VAL field to 7.

@0:=A-1;7
Same as above, because @0 is just another name for A

D:=0;@D:=A-1;7
Same as above, because D==0.

AA:="abc";7
Overwrite the string input variable AA with the string 'abc', and set the VAL field to 7.

AA:="abc";b:=0;7
Multiple store expressions, separated by ';' terminators, are legal at top level, but - as always - the expression as a whole must produce a value. This expression produces the value 7.

A+(AA:="abc";b:=0;7)
Multiple store expressions are also legal within parentheses, and again the parenthesized subexpression must produce a value. The parenthesized subexpression in this example produces the value 7, which is added to A.

Loop ("UNTIL")

The UNTIL function evaluates its expression repeatedly until the expression returns a nonzero value, or the allowed number of iterations sCalcLoopMax has been reached. When looping is done, or aborted, the expression value is returned.
UNTIL(1)
The expression 1 is evaluated, terminates the loop, and is returned. This do-nothing expression is equivalent to (1).

B:=10;UNTIL(B:=B-1;B<1)
This do-almost-nothing expression initializes B to 10, decrements it repeatedly until its value is zero, and returns the value 1 (True).

B:=9; AA:=''; UNTIL(AA:=AA+CC[B,B]; B:=B-1; B<0)
If we start with CC='abcdefghij', this expression loops backwards through CC, appending characters to produce AA='jihgfedcba'.

B:=0;AA:='';UNTIL(AA:=AA+(CC[b,b]==','?'':CC[b,b]);B:=B+1;B>LEN(CC))
This expression copies CC to AA, leaving out the commas.

AA:='';B:=1;UNTIL(A:=0;C:=UNTIL(AA:=AA+(@@B)[A,A];A:=A+1;A>1);B:=B+1;B>12)
This nested loop copies the first two characters from each of the string-input fields BB-LL, and appends them to AA. Note that the inner "UNTIL" function produces a value that must be discarded (by storing it to C), because it is part of the outer UNTIL function's expression. That expression must produce a single value, which the UNTIL function uses to determine when it's done.

 


5. 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 Timewrite output every time record is processed.
On Changewrite output every time VAL changes, i.e., every time the result of the expression changes.
When Zerowhen record is processed, write output if VAL is zero.
When Non-zerowhen record is processed, write output if VAL is non-zero.
Transition to Zerowhen record is processed, write output only if VAL is zero and last value was non-zero.
Transition to Non-zerowhen record is processed, write output only if VAL is non-zero and last value was zero.
NeverDon'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.

 


6. 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.

See the EPICS Record Reference Manual, for more on the record name (NAME) and description (DESC) fields.

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
 


7. 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
 


8. 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
 

9. 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
 


10. 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 section 11.

 

special

This is called if CALC or OCAL is changed. special calls sCalcPostfix.

 

get_value

Fills in the values of struct valueDes so that they refer to VAL.

 

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


 

11. Record Processing

11.1. process()

The process() routine implements the following algorithm:

 

1. Fetch all arguments.

 

2. Call routine sCalcPerform(), which calculates VAL from the postfix version of the expression given in CALC. 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. Check to see if monitors should be invoked.

 

6. If no output delay was specified, scan forward link if necessary, set PACT FALSE, and return.

 

11.2. 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).

 

4. If an output delay was implemented, process the forward link.

 

12. Sample Database

Here's a sample database fragment that illustrates how to include a constant literal string within a calc expression. At run time, you could enter the expression below either as
AA+printf(' %.3f',A)
or as
AA+printf(" %.3f",A)
But in a database, you don't have that freedom, because the entire expression is the value of an EPICS field, which must be enclosed in double quotes:
record(scalcout, "$(P)SRS810:$(N):SetPhas") {
    field(DESC, "Create Phase Set Str")
    field(CALC, "AA+printf(' %.3f',A)")
    field(OUT, "$(P)SRS810:$(N):WritePhas.AOUT  PP MS")
    field(PREC, "2")
    field(AA, "PHAS")
}


Tim Mooney