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66 •
Programmable Field Bus Controller 750-833
Process Image
RAM
Retain
Note
The automatic memory management can cause a data overlap. For this
reason, we recommend not to use a mix of flags and retain variables.
Code
memory
The RAM memory is used to create variables not required for
communication with the interfaces but for internal processing,
such as computation of results.
The retain memory is a non-volatile memory, i.e. all values are
retained following a voltage failure. The memory management
is automatic. In this memory area, flags for the IEC 61131-3
program are filed together with variables without memory space
addressing or variables, which are explicitly defined with "var
retain".
The IEC 61131-3 program is filed in the code memory. The
code memory is a flash ROM. Once the supply voltage is
applied, the program is transmitted from the flash to the RAM
memory. After an error-free start-up, the PFC cycle starts when
the operating mode switch is turned to its upper position or by a
start command from WAGO-I/O-PRO.
WAGO-I/O-SYSTEM 750
Bus System
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