Fbd_Math Structure - Allen-Bradley Logix5000 Reference Manual

Chapter 6 Compute/Math Instructions (CPT, ADD, SUB, MUL, DIV, MOD, SQR, SQRT, NEG, ABS)
Input Parameter Data Type
EnableIn BOOL
Source A REAL
Source B REAL
Output Parameter Data Type
EnableOut BOOL
Dest REAL
Description:
If source B is zero and
All operands are integers (SINT, INT, or
DINT)
At least one operand is a REAL
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FBD_MATH Structure

Description
Enable input. If cleared, the instruction does not execute and outputs are not updated.
Default is set.
Value of the dividend.
Valid = any float
Value of the divisor.
Valid = any float
Description
The instruction produced a valid result.
Result of the math instruction. Arithmetic status flags are set for this output.
If the Destination is not a REAL, the instruction handles the fractional portion
of the result as follows:
If source A
And Source B are not
REALs
Or Source B is a REAL
The destination is set as follows.
If Source B (the divisor) is zero:
• A minor fault occurs:
– Type 4: program fault
– Code 4: arithmetic overflow
• The destination is set as follows:
And the destination is a
SINT, INT, or DINT
REAL
Rockwell Automation Publication 1756-RM003N-EN-P - October 2011
Then the fractional Example
portion of the result
Truncates Source A
Source B
Destination
Rounds Source A
Source B
Destination
And the result is Then the destination is set to
Source A
Positive -1
Negative 0
Positive 1.$ (positive infinity)
Negative -1.$ (negative infinity)
DINT 5
DINT 3
DINT 1
REAL 5.0
DINT 3
DINT 2