Fieldbus controller 750-842
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67
Data exchange
Modular I/O System
ETHERNET TCP/IP
In addition, the controller offers further memory spaces which cannot be ac-
cessed from the fieldbus side:
RAM
The RAM memory is used to create variables not required for
communication with the interfaces but for internal processing,
such as for instance computation of results.
The retentive memory is 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 pro-
gram are filed together with variables without memory space
addressing or variables which are explicitly defined with "var
retain".
Retentive
memory
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 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
a successful start-up, the PFC cycle starts when the operating
mode switch is turned to its upper position or by a start com-
mand from WAGO-I/O-PRO 32.
3.2.5.2 Addressing
3.2.5.2.1 Addressing the I/O modules
The arrangement of the I/O modules in a node is optional.
When addressing, first of all the complex modules (modules occupying 1 or
more bytes) are taken into consideration in accordance with their physical order
behind the fieldbus controller. As such, they occupy the addresses beginning
with word 0.
Following this, the data of the other modules follow - grouped into bytes -
(modules occupying less than 1 byte). These are filled byte-by-byte according to
their physical order. As soon as a full byte is occupied by the bit oriented mod-
ules, the next byte starts automatically.
Note
For the number of input and output bits or bytes of the individually connected
bus modules please refer to the corresponding descriptions of the bus modules.
.
Note
Changing a node could result into a new structure of the process image. Also the
addresses of the process data will change. When adding modules, the process
data of all previous modules have to be taken into account.
