IDEC SMARTRELAY User Manual page 240

IDEC SmartRelay functions
4.4 Special functions list - SF
Functional description
The analog math error detection block sets the output when the referenced analog math
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 analog math error detection
block is reset with the R parameter. In 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 analog math function block executes before the analog
math error detection function block, the error is detected in the same scan cycle. If the
referenced analog math function block executes after the analog math error detection
function block, the error is detected in the next scan cycle.
Analog math error detection logic table
In the table below, Err represents the parameter of the analog math error detection instruction
that selects which type of error to detect. ZD represents the zero division bit set by the analog
math at the end of its execution: 1 if the error occurred, 0 if not. OF represents the overflow bit
set by the analog math: 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 analog math
instruction. Q represents the output of the analog math 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.
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ZD OF
1 x
0 x
x 1
x 0
1 0
0 1
1 1
0 0
Q
1
0
1
0
1
1
1
0
IDEC SmartRelay Manual