Lenze PLC Designer PLC Designer (R3-1) - Manual (Page 1102)

L-force | PLC Designer
Programming Reference
1100 DMS 4.1 EN 03/2011 TD29
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Address
When specifying an address, the memory location and size are indicated by special
character sequences.
Syntax:
%
The following memory area prefixes are supported:
I Input (physical inputs via input driver, "sensors")
Q Output (physical outputs via output driver, "actors")
M Memory location
The following size prefixes are supported:
X Single bit
None Single bit
B Byte (8 Bits)
W Word (16 Bits)
D Double word (32 Bits)
Examples:
%QX7.5 and %Q7.5 Output bit 7.5
%IW215 Input word 215
%QB7 Output byte 7
%MD48 Double word in memory position 48 in the memory location.
%IW2.5.7.1 Interpretation depends on the current PLC Configuration (see below)
ivar AT %IW0 : WORD; Example of a variable declaration including an address assignment
Make sure to use a valid address:
For assigning a valid address within an application, first of all you must know the
appropriate position within the process image, that is the memory area to be used:
Input (I), Output (Q) or Memory (M) area, see above. Further on specify the desired size:
bit, byte, word, dword (see above: X, B, W, D)
A decisive role plays the current device configuration and settings (hardware structure,
device description, I/O settings). Especially consider the differences in address
interpretation between devices using "byte addressing mode" or those using word
oriented "IEC addressing mode".
So depending on the size and addressing mode different memory cells might be
addressed by the same address definition.
See the table below for a comparison of byte addressing and word oriented IEC
addressing for bits, bytes, words and dwords. After all it visualizes the overlapping
memory areas in case of byte addressing mode (see an example following to the table.