PLC concepts
5.2 Data storage, memory areas, I/O and addressing
S7-1200 Programmable controller
122 System Manual, V4.2, 09/2016, A5E02486680-AK
Note
When you specify an absolute address in LAD or FBD, STEP 7 precedes this address with a
"%" character to indicate that it is an absolute address.
While programming, you can enter
an absolute address either with or without the "%" character (for example %I0.0 or I.0). If
omitted, STEP
7 supplies the "%" character.
In SCL, you must enter the "%" before the address to indicate that it is an absolute a
ddress.
7 generates an undefined tag error at compile time
Configuring the I/O in the CPU and I/O modules
When you add a CPU and I/O modules to your
device configuration, STEP
7 automatically assigns
I and
Q addresses. You can change the default
addressing by selecting the address field in the
device configuration and entering new numbers.
STEP 7 assigns digital inputs and outputs in
groups of 8 points (1 byte), whether the module
uses all the points or not.
STEP 7 allocates analog inputs and outputs in
groups of 2, where each analog poing occupies
2 bytes (16 bits).
The figure shows an example of a CPU 1214C with two SMs and one SB. In this example,
you could change the address of the DI8 module to 2 instead of 8. The tool assists you by
changing address ranges that are the wrong size or conflict with other addresses.
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