IDEC SMARTRELAY User Manual page 238

IDEC SmartRelay functions
4.4 Special functions list - SF
Functional description
The analog math function combines the four operations and three operators to form an
equation. The operator can be any one of the four standard operators: +, -, *, or /. The priority
of operators is determined by "( )" and "[ ]", in which "( )" has a higher priority. The operand
values can reference another previously-defined function to provide the value. The analog
math function rounds the result to the nearest integer value.
The number of operand values is fixed at four and the number of operators is fixed at 3. If you
need to use fewer operands, use constructions such as + 0 or * 1 to fill the remaining
parameters.
You can also configure the behavior of the function when the Enable parameter En=0. The
function block can either retain its last value, or be set to 0. If the parameter Qen → 0 = 0,
then the function sets AQ to 0 when En=0. If the parameter Qen → 0 = 1, then the function
leaves AQ at its last value when En=0.
Possible errors: zero division and overflow
If the analog math function block execution results in zero division or overflow, it sets internal
bits that indicate the type of error that occurred. You can program an analog math error
detection function block in your circuit program to detect these errors, and to control the
program behavior as needed. You program one analog math error detection function block to
reference one specific analog math function block.
Examples
The following tables show some simple example analog math block parameters, and the
resulting equations and output values:
V1
12
Equation: [12 + (6 / 3)] - 1
Result: 13
V1
2
Equation: 2 + [3 * (1 + 4)]
Result: 17
V1
100
Equation: (100 - 25) / [2 + 1]
Result: 25
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Op1 V2
(Priority)
[+] 6
Op1 V2
(Priority)
(+) 3
Op1 V2
(Priority)
(-) 25
Op2 V3
(Priority)
(/) 3
Op2 V3
(Priority)
[*] 1
Op2 V3
(Priority)
/ 2
Op3 V4
(Priority)
- 1
Op3 V4
(Priority)
+ 4
Op3 V4
(Priority)
[+] 1
IDEC SmartRelay Manual