Lenze PLC Designer PLC Designer (R3-1) - Manual (Page 863)

L-force | PLC Designer
Device Editors
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DMS 4.1 EN 03/2011 TD29 861
General on I/O mapping
Whether at all an I/O mapping can be configured for the current device, depends on
the device; it might be that the dialog only is used to show the implicitly created
device instance, see below: "IEC Objects".
Basically the following must be noticed for the mapping of I/Os on variables:
• Variables requiring an input cannot be accessed by writing.
• Instead of using the I/O Mapping dialog an address also can be assigned to a
variable via the "AT declaration". On this regard the following: 1. "AT declarations"
only can be used with local or global variables, not however with input and output
variables of POUs. 2. The possibility of generating force variables for I/Os (see
below: Implicit variables for forcing I/Os) will not be available for "AT declarations".
3. If "AT declarations" are used with structure or function block members, all
instances will access the same memory location, which corresponds to "static
variables" in classic programming languages like for example C.
• The memory layout of structures is determined by the target device.
• For each variable which is assigned to an I/O channel in the I/O Mapping dialog,
"force variables" can be created during a build run of the application. These might
be used for forcing the input resp. output value during the commissioning of a
machine, e.g. via a visualization (HMI). See below: Implicit variables for forcing
I/Os.
Using the dialog
Abb. 474 Device dialog, I/O Mapping, Example