4.3.7
Extended AUTOMATIC
WARM RESTART with the
CPU 948 (HOT RESTART)
The "HOT RESTART" mode specified in the IEC 1131 standard, part
1 is also possible in the CPU 948. The "HOT RESTART" is a warm
restart controlled by a battery-backed clock (according to IEC 1131).
The clock monitors the time between switching off and switching on
the power supply for the CPU. Whether or not a warm restart is then
permitted depends on the time elapsed.
The automatic "HOT RESTART" of the CPU 948 is not supported
directly by the system program, which means that you must program
this yourself.
The basic functions available are the AUTOMATIC WARM
RESTART (OB 22) and the real time clock which although internal is
backed up by an external battery.
A "HOT RESTART" is programmed as shown below:
Mode
Activity/block
RUN
Save time (time of day and date) regularly from the external clock in defined memory
cells (e.g. in data words):
-
at the end of the cycle in OB 1
or
-
time-controlled by timed interrupts (e.g. OB 10), if higher accuracy is necessary
AUTO-
MATIC
WARM
RESTART
OB 22
Calculate down time:
T
down
= first time value after return of power - last time value saved before power failure
IF ...
THEN...
Down time > default maximum value
Stop warm restart
(STP operation)
or
execute modified warm restart
Down time
≤
default maximum value
Continue warm restart
START-UP Mode
CPU 948 Programming Guide
C79000-G8576-C848-04
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Summary of Contents for CPU 948
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Page 72: ...Data Blocks CPU 948 Programming Guide 2 42 C79000 G8576 C848 04 ...
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Page 324: ...Examples of Parameter Assignment CPU 948 Programming Guide 7 18 C79000 G8576 C848 04 ...
Page 326: ...Contents CPU 948 Programming Guide 8 2 C79000 G8576 C848 04 ...
Page 370: ...Addressable System Data Area CPU 948 Programming Guide 8 46 C79000 G8576 C848 04 ...
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Page 486: ...Contents CPU 948 Programming Guide 11 2 C79000 G8576 C848 04 ...
Page 522: ...PG Functions via the S5 Bus CPU 948 Programming Guide 11 38 C79000 G8576 C848 04 ...
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Page 538: ...Contents CPU 948 Programming Guide 13 2 C79000 G8576 C848 04 ...
Page 546: ...List of Key Words CPU 948 Programming Guide Index 6 C79000 G8576 C848 04 ...