Monitoring Controller Operations
Chapter 12
12–11
3. Increment the counter by turning on I:1/0. The accumulator value equals
the preset value, the done bit DN (bit 13) is set, and rung 2 is true.
4. Increment the counter again. The is in an overflow condition, setting the
overflow bit OV (bit 12). Rung 3 in the ladder program is true. The
display changes as follows:
Counter
C5:0
CU
CD
DN
OV
UN
UA
STATUS
0
0
1
1
0
0
PRESET
32767
ACCUM
–32768
STATUS=–32768
RUN
F1
F2
F3
F4
F5
NEXT_PG PREV_PG
ADDRESS NEXT_FL PREV_FL
The accumulator is on the 32768th count, shown as –32678. As the count
continues to increment, the accumulator shows negative numbers of
decreasing absolute value.