Technical data

Appendix
27.2 Memory Areas of S7 CPUs
Programming with STEP 7
Manual, 05/2010, A5E02789666-01 575
Address Area Access via Units of
Following Size
S7 Notation
(IEC)
Description
Data block, opened with
"OPN DB":
DB Data blocks contain information for the
program. They can be defined for
general use by all logic blocks (shared
DBs) or they are assigned to a specific
FB or SFB (instance DB).
Data bit DBX
Data byte DBB
Data word DBW
Data double word DBD
Data block, opened with
"OPN DI":
DI
Data bit DIX
Data byte DIB
Data word DIW
Data block
Data double word DID
Local data bit L This area contains the temporary data
of a block while the block is being
executed. The L stack also provides
memory for transferring block
parameters and for recording interim
results from Ladder Logic networks.
Local data byte LB
Local data word LW
Local data
Local data double word LD
Peripheral input byte PIB The peripheral input and output areas
allow direct access to central and
distributed input and output modules
(DP).
Peripheral input word PIW
Peripheral (I/O) area:
inputs
Peripheral input double
word
PID
Peripheral output byte PQB
Peripheral output word PQW
Peripheral (I/O) area:
outputs
Peripheral output double
word
PQD
Refer to the following CPU manuals or instruction lists for information on which address areas are
possible for your CPU:
• "S7-300 Programmable Controller, Hardware and Installation" Manual
• "S7-400, M7-400 Programmable Controllers, Module Specifications" Reference Manual
• "S7-300 Programmable Controller, Instruction List"
• "S7-400 Programmable Controller, Reference Guide"