Siemens SIMATIC S5-115U, Руководство пользователя

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S5-115U Manual PLC System Start-Up and Program Test
Special Points When Setting Up Data Blocks
• Data blocks generated in the control program with the "G DB" operation are automatically
dumped by the operating system direct in internal program memory.
The contents of the data blocks can be changed using STEP 5 operations.
• Data blocks that have been transferred to an E(E)PROM submodule cannot be changed by the
control program in the case of CPU 941 and CPU 942; they are suitable for e.g. fixed recipes.
The contents of the memory submodule are copied to internal program memory after
POWER ON in the case of the CPU 943 and CPU 944; this means that the contents of the data
blocks can also be changed in the user program. However, after each POWER ON (and after
Overall Reset), the "old" data blocks from the memory submodule are copied into internal
program memory; the "current" contents are lost.
• If you want to change the contents of data blocks during execution of the control program,
these data blocks must be transferred by the programmer direct over the programmer
interface to the CPU in the case of the CPU 941 and CPU 942, or they are generated with the
"G DB" operation.
4.2.3 Determining the Retentive Feature of Timers, Counters and Flags
Use the "Presetting the retentive feature/Overall Reset" switch on the operator panel of the CPU
to determine the behaviour of timers, counters and flags at cold restart (both manually and
automatically after power restore).
Timers, counters and flags are "retentive" if they do
not lose their contents at cold restart. Those
timers, counters and flags which are reset at cold restart are "nonretentive".
The following retentive feature is set as default
after Overall Reset:
All timers, counters and flags are nonretentive in the NR switch position. In the RE switch position,
half of all timers, counters and flags are retentive:
Table 4-1. Preset Retentive Feature of the CPUs 941 to 944 after Overall Reset
Switch Position Flags Timers Counters
F 0.0 to F 127.7
retentive
F128.0 to 255.7
nonretentive
T0 to T63 retentive
T64 to T127
nonretentive
C0 to C63 retentive
C64 to C127
nonretentive
NR (nonretentive) No retentive flags No retentive timers No retentive counters
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RE (retentive)
If the battery fails on a cold restart after POWER UP and the switch is in the RE
(retentive) position, the programmable controller stops (memory error).
Note
EWA 4NEB 811 6130-02b
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