Siemens S7-1200 - Page 109

PLC concepts
4.2 Data storage, memory areas, I/O and addressing
S7-1200 Programmable controller
System Manual, 03/2014, A5E02486680-AG
109
Table 4- 24 Absolute addressing for DB memory
Bit DB[data block number].DBX[byte
address].[bit address]
DB1.DBX2.3
Byte, Word, or Double
Word
DB[data block number].DB [size][starting
byte address]
DB1.DBB4, DB10.DBW2,
DB20.DBD8
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 witho
ut 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 address.
Without the "%", STEP
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
configuration screen, I and Q ad
dresses are
automatically assigned. You can change the
default addressing by selecting the address field in
the device configuration and typing new numbers.
•
Digital inputs and outputs are assigned in
groups of 8 points (1 byte), whether the module
uses all the points or not.
•
Analog inputs and outputs are assigned in
groups of 2 points (4 bytes).
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.