Fieldbus coupler/controller |
• 47 |
Fieldbus controller 750-819 |
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3.2.6.2.2 Addressing the PFC variables
The PFC variables are to be found in the memory ranging from word 256 to 512. When programming an internal PLC application, the CPU accesses PFC variables via absolute addresses. However, depending on the data type used, the same physical address space is addressed differently.
Byte addresses |
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Word addresses |
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Double word addresses |
1024 |
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512 |
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256 |
512 |
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256 |
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128 |
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511 |
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255 |
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127 |
0 |
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0 |
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0 |
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Tab. 3-3: Utiliztation of the address range for PFC variables |
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Bit Address |
Word address .0 to .15 |
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Byte Address |
1st byte: |
2 x Word address |
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2nd byte: |
2 x Word address + 1 |
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DWord Address |
lower section: Word address (even numbers) / 2 |
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upper section: Word address (odd numbers) / 2, rounded off |
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Attention
To avoid address overlapping all the previous address assignments must be taken into account!
3.2.6.2.2.1Template
Addressing becomes very complex when using a free memory organisation and mixing different data types.
Therefore, the template (Template_750_819.pro) for the IEC 61131-3 programming tool WAGO-I/O-PRO 32 enables considerable work saving. The template predefines memory areas, so that address overlapping can generally be excluded.
More information
i The file "Template_750_819.pro" is in the "Template" directory of the programming tool WAGO-I/O-PRO 32 CD-ROM (Item-No.: 759-332/000-001). After selecting "Open" and "Save as..." the file is used as template for a new project.
The memory spaces of PFC variables are divided into data type areas. This results in the maximum number of predefined variables:
Modular I/O System
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