Siemens LOGO! Series Manual page 269

Parameter MathBN
The value for the MathBN parameter references the block number of an already-
programmed mathematic instruction function block.
Functional description
The mathematic instruction error detection block sets the output when the referenced
mathematic instruction function block has an error. You can program the function to set the
output on a zero division error, an overflow error, or when either type of error occurs.
If AutoRst is set, the output is reset prior to the next execution of the function block. If
AutoRst is not set, then whenever the output is set it remains set until the mathematic
instruction error detection block is reset with the R parameter. This way, even if the error
subsequently clears, the circuit program still has knowledge that an error did occur at some
point.
In any scan cycle, if the referenced mathematic instruction function block executes before
the mathematic instruction error detection function block, the error is detected in the same
scan cycle. if the referenced mathematic instruction function block executes after the
mathematic instruction error detection function block, the error is detected in the next scan
cycle
Mathematic instruction error detection logic table
In the table below, Err represents the parameter of the mathematic instruction error detection
instruction that selects which type of error to detect. ZD represents the zero division bit set
by the mathematic instruction at the end of its execution: 1 if the error occurred, 0 if not. OF
represents the overflow bit set by the mathematic instruction: 1 if the error occurred, 0 if not.
The ZD/OF Err parameter represents the logical OR of the zero division bit and overflow bit
of the referenced mathematic instruction. Q represents the output of the mathematic
instruction error detection function. An "x" indicates that the bit can be either 0 or 1 with no
influence on the output.
Err
ZD
ZD
OF
OF
ZD/OF
ZD/OF
ZD/OF
ZD/OF
If the MathBN parameter is null, then the output Q is always 0.
LOGO!
Manual, 04/2011, A5E03556174-01
ZD
1
0
x
x
1
0
1
0
4.4 Special functions list - SF
OF
x
x
1
0
0
1
1
0
LOGO! functions
Q
1
0
1
0
1
1
1
0
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