Siemens LOGO! Manual page 210

LOGO! functions
4.4 Special functions list - SF
Select the required function by the block number. For information on parameter defaults,
refer to the On-delay (Page 123) topic.
Note
If the analog value for parameter V1, V2, V3 or V4 is derived from another already-
programmed function whose actual value exceeds the value range for V1 ... V4, LOGO! will
display the limit value: -32768 if the value is less than the lower range or 32767 if the value is
greater than the upper range).
Parameters p (number of decimals)
Parameter p applies only to the display of Value1, Value2, Value3, Value4 and AQ in a
message text.
Functional Description
The analog math function combines the four operands and three operators to form an
equation. The operator can be any one of the four standard operators: +, -, *, or /. For each
operator, you must set a unique priority of High (H), Medium (M), or Low (L). The high
operation will be performed first, followed by the medium operation, and then by the low
operation. You must have exactly one operation of each 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.
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Manual, 10/2017, A5E01248535-AA
LOGO!