Siemens SIMATIC S7-400 CP 440 - Programming the Function Blocks

Communication via Function Blocks
6.4 Programming the Function Blocks
Point-to-point connection CP 440 Installation and Parameter Assignment
Manual, 09/2007, A5E00057742-03
101
6.4 Programming the Function Blocks
6.4.1 General Information on Data Block Assignment
Introduction
This section is intended for users upgrading from SIMATIC S5 to SIMATIC S7. The various
subsections contain important information on programming function blocks in STEP 7.
Addressing
The data operands in data blocks are addressed bytewise in STEP 7 (in contrast to STEP 5,
where addressing is word-based). You therefore have to convert the addresses of the data
operands.
67(367(3
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'5>Q@
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'%:>Q@
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Figure 6-4 Contrasting Data Addressing in STEP 5 and STEP 7
The address of a data word in STEP 7 is doubled compared to STEP 5. It is no longer
divided into a right and a left data byte. Bit numbering is always from 0 to 7.
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