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S5-115U Manual
7.5
Processing Blocks
Section 8 describes how to use blocks. In addition, Chapter 7 describes all operations necessary to
work with blocks.
Of course, blocks that have already been programmed can be changed. Possibilities for changing
blocks are described here only briefly. The operating instructions for the particular programmer
used explain the necessary steps in detail.
7.5.1
Modifying the Program
You can modify the program, regardless of block type, with the following programmer functions:
•
INPUT
•
OUTPUT
•
STATUS (see Chapter 4)
With the above functions, you can make the following changes:
•
insert, delete, or overwrite statements
•
insert or delete segments.
7.5.2
Modifying Blocks
Program modifications relate to the contents of a block. You can also delete or overwrite entire
blocks. However, this does not delete the blocks in the program memory. Instead, it simply
invalidates the blocks. The memory locations of these blocks cannot be written to again. As a
result, new blocks might not be accepted. The programmer reports the error message "No
memory space". Eliminate this by compressing the PLC memory.
7.5.3
Compressing the Program Memory
Figure 7-10 explains compressing. Internally one block is shifted per cycle.
Program memory
Valid
Blocks
Invalid
Input not
possible
PB
EWA 4NEB 811 6130-02b
RAM
Compression
Available
memory
locations
Figure 7-10. Compression Process
Introduction to STEP 5
Program memory
RAM
Input
possible
PB
7-25
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