Programming Technique
Chapter 25
25-4
The switch assembly on the I/O chassis determines how and when
EEPROM to CMOS RAM transfer occurs. A transfer takes place if any
change of CMOS RAM memory content occurs while the battery was
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. A 24-hour clock program (Figure 25.5) is an example of
cascading timers. Again, we emphasize not to enter these instructions
using your online production equipment.
Figure 25.5
24Hour 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
inaccurate program timing.
Cascading Timers
