Processing Blocks - Siemens SIMATIC S5-100U System Manual

Introduction to STEP 5
7.5

Processing Blocks

Earlier sections in this chapter described how to use blocks. Chapter 8 introduces all of the
operations required to work with blocks. You can change any block that has been programmed.
The following sections will deal only briefly with the different ways you can change blocks. Refer to
the operator's guide for your programmer for more detailed information on changing blocks.
7.5.1 Changing Programs
You can use the following programmer functions to make program changes with any block type.
• INPUT
• OUTPUT
• STATUS (see section 4.5)
These three programmer functions make it possible for you to make the following types of changes:
• Delete, insert, or overwrite statements.
• Insert or delete segments.
7.5.2 Changing Blocks
Program changes refer to changing the contents of a block. You can also delete or overwrite a
complete block. When you delete a block, it is not deleted from the program memory but simply
becomes invalid. You cannot enter new information in the memory location of an invalid block. This
may cause new blocks not to be accepted. If a new block is not accepted, then the PG transmits
the "no space available" error message. You can make more space by compressing the
programmable controller memory.
7.5.3 Compressing the Program Memory
Figure 7-15 illustrates what takes place in the program memory during a COMPRESS operation.
Internally, one block is shifted per cycle.
Program memory
Valid
blocks
Invalid
Input not
possible
PB
Figure 7-15. Compressing the Program Memory
7-30
RAM
Compress
Available
memory space
Program memory
RAM
EWA 4NEB 812 6120-02b
S5-100U
Input
possible
PB