Rockwell Automation 1772-LS_LSP,D17726.8.6 PROG/OPER MANUAL-MINI PLC-2/05 - Manual (Page 212)

Programming Techniques
Chapter 18
18-4
Switches on the switch assembly of the I/O chassis determine how and
when EEPROM to CMOS RAM transfer occurs. A transfer takes place
when any change of CMOS RAM memory content occurs while the
battery is being changed. If a transfer occurs (memory was altered), the
data table contains the values programmed into the EEPROM. If transfer
did not occur, memory did not change. The data table contains the values
that existed at the time system power was removed.
Cascading is a programming technique that extends the ranges of timer
and/or counter instructions beyond the maximum values that may be
accumulated. Figure 18.5 illustrates a 24-hour clock program. Again, we
emphasize not to enter these instructions using your on-line
production equipment.
Figure 18.5
24 Hour Clock
030
15
030
1.0
15
030 031
CTU
TON
PR 060
AC 005
PR 060
AC 000
15
031 032
CTU
PR 060
AC 000
15
031 032
CTR
PR 060
AC 000
15
032 032
CTR
PR 024
AC 000
Rung 1
Rung 2
Rung 3
Rung 4
Rung 5
ATTENTION: Do not use the clock program as a real time
clock device. Failure to observe this caution may result in an
inaccurate program.
Cascading Timers