Function blocks (FB/FX)
You use function blocks to program frequently recurring and/or
complex functions (e.g. digital functions, sequence control systems,
closed loop controls and signalling functions).
A function block can be called several times by higher order blocks
and supplied with new operands (assigned parameters) at each call.
Using block type FX doubles the maximum number of possible function
blocks.
Data blocks (DB/DX)
Data blocks contain the (fixed or variable) data with which the user
program works. This type of block contains no STEP 5 statements and
has a distinctly different function from the other blocks. Using block
type DX doubles the number of possible data blocks.
Formal structure
of the blocks
All blocks consist of the following two parts:
••
a block header
and
••
a block body
Block header
The block header is always 5 words long and contains information for
block management in the PG and data for the system program.
Block body
Depending on the block type, the block body contains the following:
••
STEP-5 operations (in OB, PB, SB, FB, FX),
••
variable or constant data (in DB, DX)
and
••
a formal operand list (in FB, FX).
STEP 5 Programming Language
CPU 948 Programming Guide
C79000-G8576-C848-04
2 - 13
Summary of Contents for CPU 948
Page 10: ...Contents CPU 948 Programming Guide 1 2 C79000 G8576 C848 04 ...
Page 32: ...Contents CPU 948 Programming Guide 2 2 C79000 G8576 C848 04 ...
Page 72: ...Data Blocks CPU 948 Programming Guide 2 42 C79000 G8576 C848 04 ...
Page 74: ...Contents CPU 948 Programming Guide 3 2 C79000 G8576 C848 04 ...
Page 154: ...Contents CPU 948 Programming Guide 4 2 C79000 G8576 C848 04 ...
Page 200: ...Contents CPU 948 Programming Guide 5 2 C79000 G8576 C848 04 ...
Page 308: ...Contents CPU 948 Programming Guide 7 2 C79000 G8576 C848 04 ...
Page 324: ...Examples of Parameter Assignment CPU 948 Programming Guide 7 18 C79000 G8576 C848 04 ...
Page 326: ...Contents CPU 948 Programming Guide 8 2 C79000 G8576 C848 04 ...
Page 370: ...Addressable System Data Area CPU 948 Programming Guide 8 46 C79000 G8576 C848 04 ...
Page 372: ...Contents CPU 948 Programming Guide 9 2 C79000 G8576 C848 04 ...
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 ...
Page 524: ...Contents CPU 948 Programming Guide 12 2 C79000 G8576 C848 04 ...
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 ...