Conversion Between Optimized And Non-Optimized Tags - Siemens S7-1200 Programming Manualline

2 S7-1200/1500 Innovations
2.6 Optimized blocks
The retentivity of tags of a global DB is defined directly in the global DB. The
default setting is non-retentive.
The retentivity of tags of one instance is defined in the function block (not in the
instance DB).These settings then apply to all instances of this FB.
Access types for optimized and non-optimized blocks
The following table displays all access types to blocks.
Table 2-6: Access types
Symbolic
Indexed (fields)
Slice accesses
AT instruction
Direct absolute
Indirect absolute (pointer)
Downloading without
reinitialization
Note You will find further information in the following entries:
What differences should you watch out for between optimized data storage and
the standard type of block access in STEP 7 (TIA Portal) V12?
http://support.automation.siemens.com/WW/view/en/67655611
What properties do you have to pay attention to in STEP 7 V11 for the
instructions "READ_DBL" and "WRIT_DBL", when you are using DBs with
optimized access?
http://support.automation.siemens.com/WW/view/en/51434748
2.6.4

Conversion between optimized and non-optimized tags

The general recommendation is to work with optimized tags. However, if you want
to keep your previous programming in individual cases, this leads to a mixture of
optimized and non-optimized data storage in the program.
The system recognizes the internal storage of each tag, no matter if structured
(derived from a user-defined data type) or elementary (INT, LREAL, etc.).
In the case of type-identical allocations between two tags with different storage
locations, the system converts automatically. In the case of structured tags, this
conversion requires performance and should therefore be avoided, if possible.
Programming Guideline for S7-1200/1500
V1.2, Entry ID: 81318674
Access type Optimized block
(Alternatively: slice access)
(Alternatively: ARRAY with
index)
(Alternatively: VARIANT /
ARRAY with index)
Non-optimized
block
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