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Introduction to STEP 5
Block Structure
Each block consists of the following:
•
Block header specifying the block type, number, and length.
The programmer generates the block header when it transforms the block.
•
Block body with the STEP 5 program or data.
Absolute
byte adresses
(in ascending
order)
Programming
Blocks are programmed with the "LAD, CSF, STL" software package. See your programmer
manual for details of programming individual blocks.
7.3.1 Organization Blocks (OBs)
Organization blocks are the interface between the operating system and the control program;
they can be divided into three groups:
•
An organization block is called cyclically by the operating system (OB1)
•
Some organization blocks are event-driven or time-controlled; i.e. they are called by
-
STOP RUN or POWER OFF POWER ON transitions (OB21, OB22)
-
Interrupts (OB2 to OB6)
-
Programming errors or PLC faults (OB19, OB23, OB24, OB27, OB32, OB34)
-
Expiry of an interval (OB10 to OB13)
•
Other organization blocks represent operating functions (similar to integral function blocks),
which can be called from the control program (see Chapter 11).
7-8
Figure 7-3. Structure of a Block Header
S5-115U Manual
Synchronization
pattern
Block type
Block number
Programmer ID
Library
number
Block length
EWA 4NEB 811 6130-02b
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