Rockwell Automation 1761 MicroLogix 1000 Programmable Controllers - Manual (Page 298)

Preface MicroLogix 1000 Programmable Controllers User Manual
B–10
Address Bit Classification Description
S:2/14 Math Overflow
Selection Dynamic
Configuration Set this bit when you intend to use 32-bit
addition and subtraction. When S:2/14 is set,
and the result of an ADD, SUB, MUL, or DIV
instruction cannot be represented in the
destination address (underflow or overflow),
•
the overflow bit S:0/1 is set,
•
the overflow trap bit S:5/0 is set,
•
and the destination address contains the
unsigned truncated least significant 16 bits
of the result.
The default condition of S:2/14 is reset (0).
When S:2/14 is reset, and the result of an
ADD, SUB, MUL, or DIV instruction cannot be
represented in the destination address
(underflow or overflow),
•
the overflow bit S:0/1 is set,
•
the overflow trap bit S:5/0 is set,
•
and the destination address contains
32767 if the result is positive or – 32768 if
the result is negative.
Note, the status of bit S:2/14 has no effect on
the DDV instruction. Also, it has no effect on
the math register content when using MUL and
DIV instructions.
To provide protection from inadvertent
alteration of your selection, program an
unconditional OTL instruction at address
S:2/14 to ensure the new math overflow
operation. Program an unconditional OTU
instruction at address S:2/14 to ensure the
original math overflow operation.
S:2/15 Reserved NA NA