ABB AC 800M Library Object Style Manual page 92

Control Module Types
The code in the control module type should not be divided in code blocks for any
other reasons than taking advantage of the code sorting. Unnecessary code blocks
will cost extra execution time, especially in SIL-applications, and might danger the
code sorting.
A compiler switch exists to rule the code sorting loop detection. Code sorting loops
may hazard the object functionality at code modification elsewhere. It is
recommended to avoid and remove all kind of sorting loops before any download to
a controller takes place. It is also recommended to keep the compiler switch as
'Error' to avoid unforeseen errors.
The operation allowed on a parameter is governed by the type description keyword
(see also
to the code block in question, but the rules for reading and writing is given in
Table
Table 12. Rules for code block read and write operation to a control module
Keyword
IN
OUT
IN(OUT) The parameter is both read and written, but mostly written.
OUT(IN) The parameter is both read and written, but mostly read.
NODE
EDIT
Some special purpose parameters do not obey the above rules.
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Type Description Keyword
12.
Rules for read/write operations to Control Module parameters from
a external code block
The parameter is written to and read from.
The parameter is only read.
Only connected. Read and write operation are done by other control
module.
Only written to, and only first scan value will affect the control module.
InteractionPar is used for operator interaction, and is allowed to be both read
and write.
I/O parameters of data types BoolIO, RealIO, DIntIO or DwordIO should only
be connected.
Connection parameters for communication between control modules, should
only be connected.
Section 6 Program Code Issues
on page 32). All parameters can be connected
3BSE042835-600