2.3
Function Blocks
Function blocks (FB/FX) are also parts of the user program just like
program blocks. FX function blocks have the same structure as FB
function blocks and are programmed in the same way.
You use function blocks to implement frequently recurring or very
complex functions. In the user program, each function block represents a
complex complete function. You can obtain function blocks as follows:
••
as a software product from SIEMENS (standard function blocks
on diskette - see /11/); with these function blocks you can generate
user programs for fast and simple open loop control, signalling,
closed loop control and logging;
or
••
you can program function blocks yourself.
Compared with organization, program and sequence blocks, function
blocks have the following four essential differences:
OB, PB, SB
FB/FX
1.
Range of operations
only basic operations
- basic operations,
- supplementary operations
- system operations
2.
Method of representation
programming and call
in STL, LAD, CSF
programming only in AWL
3.
Name
name environment not
possible
(only number)
in addition to the number
a name with max. 8 chars. can
be assigned
4.
Operands
none
formal operands (block
parameters).
When the block is called
formal operands are assigned
actual operands
Function Blocks
CPU 948 Programming Guide
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Summary of Contents for CPU 948
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Page 72: ...Data Blocks CPU 948 Programming Guide 2 42 C79000 G8576 C848 04 ...
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Page 324: ...Examples of Parameter Assignment CPU 948 Programming Guide 7 18 C79000 G8576 C848 04 ...
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Page 370: ...Addressable System Data Area CPU 948 Programming Guide 8 46 C79000 G8576 C848 04 ...
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Page 486: ...Contents CPU 948 Programming Guide 11 2 C79000 G8576 C848 04 ...
Page 522: ...PG Functions via the S5 Bus CPU 948 Programming Guide 11 38 C79000 G8576 C848 04 ...
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Page 538: ...Contents CPU 948 Programming Guide 13 2 C79000 G8576 C848 04 ...
Page 546: ...List of Key Words CPU 948 Programming Guide Index 6 C79000 G8576 C848 04 ...