GE PACSystems RXi User Manual page 116

Arguments or actual parameters are passed into a parameterized block when a
parameterized block call is executed. In general, arguments to formal parameters may come
from any memory type, may be data flow, and may be constants (when the formal
parameter's LENGTH is 1). The following list contains the restrictions on arguments relative
to this general rule:
■
%S memory addresses cannot be used as arguments to any output parameter. This is
because user logic is not allowed to write to %S memory.
■
Indirect references used as arguments are resolved immediately before the
parameterized block is called, and the corresponding direct reference is passed into the
block. For example, where %R1 contains the value 10 and @R1 is used as an argument
to a call, immediately before calling the block, @R1 is resolved to be %R10, and %R10 is
passed in as the argument to the block. During execution of the block, the argument
remains as %R10, regardless of whether the value in %R1 changes.
In general, formal parameters within a parameterized block may be used with any instruction
or with any block call, as long as their TYPE and LENGTH are compatible with what the
instruction, function, or block call requires. The following list contains the restrictions on
formal parameters relative to this general rule:
■
Formal parameters cannot be used on legacy transitional contacts or coils, or on FAULT,
NOFLT, HIALM, or LOALM contacts. However, formal parameters can be used on IEC
transitional contacts and coils.
■
Formal BOOL input parameters cannot be used on coils or as output arguments to a
function or to a block call.
■
Formal parameters cannot be used with the DO I/O function.
■
Formal parameters cannot be used with indirect referencing.
GFK-2816F August 2015
Chapter 6. Program Organization
103