Rockwell Automation Publication 1756-RM003N-EN-P - October 2011 645
Common Attributes Appendix A
S:V Overflow flag
The controller sets the overflow flag when the
result of an arithmetic operation resulted in an
overflow. This flag can be used with only the XIC,
XIO, OTE, OTL and OTU relay instructions or in
structured text like a Boolean variable. You can
use this flag to check that the result of an
operation is still in range. For example, adding 1
to a SINT generates an overflow when the value
goes from 127…128.
The overlow flag generates a minor fault when it
transitions from false to true.
This math status flag is cleared at the start of
executing an instruction capable of setting this
flag.
Sometimes called the ‘overflow’ bit.
The MOD instruction does not capture an
overflow that may have occurred during the
calculation. If an overflow occurs, a minor fault
will be generated, but the S:V bit will not be set.
S:C Carry flag
The controller sets the carry flag when the result
of an arithmetic operation resulted in the
generation of a carry out of the most significant
bit. This flag can be used with only the XIC, XIO,
OTE, OTU and OTL relay instructions or in
structured text like a Boolean variable.
This math status flag is cleared at the start of
executing an instruction capable of setting this
flag.
Sometimes called the ‘carry’ bit.
S:MINOR Minor fault flag
The controller sets the minor fault flag when
there is at least one minor program fault. This
flag can be used with only the XIC, XIO, OTE, OTL
and OTU relay instructions or in structured text
like a Boolean variable. You could use this flag to
test that a minor fault has occurred and take
appropriate action. This bit is triggered only by
programming faults (like overflow). It will not be
triggered by a battery fault. The bit is cleared on
every scan. An OTL can be used to explicitly
program a minor fault occurrence.
Status Flag Description
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