
17-2
Ladder Logic (LAD) for S7-300 and S7-400
C79000-G7076-C504-02
17.1 Open Data Block: DB or DI
You can use the Open Data Block: DB or DI instruction to open an already
existing data block as DB or DI. The number of the data block is transferred
in the DB or DI register. The subsequent DB and DI commands access the
corresponding blocks depending on the register contents.
Table 17-1 Open Data Block: DB or DI Element and Parameters, with International Short Name
LAD Element Parameter Data Type Memory Area Description
<DB number> or
<DI number>
OPN
Number of
DB or DI
BLOCK_DB –
The number range of DB or DI
depends on your CPU.
Table 17-2 Open Data Block: DB or DI Element and Parameters, with SIMATIC Short Name
LAD Element Parameter Data Type Memory Area Description
<DB number> or
<DI number>
AUF
Number of
DB or DI
BLOCK_DB –
The number range of DB or DI
depends on your CPU.
Status Word Bits
BR CC 1 CC 0 OV OS OR STA RLO FC
Write – – – – – – – – –
DB10 is the currently opened
data block. That is why the
scan at DBX0.0 refers to bit 0
of data byte 0 of data block
DB10. The signal state of this
bit is assigned to output Q 4.0.
OPN
DB10
DBX0.0 Q 4.0
This instruction does not read or change the bits of the status word.
Figure 17-1 Open Data Block: DB or DI
Description
Data Block Instructions
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