Word-For-Word Changes - GE PACSystems RXi User Manual

Chapter 7. CPU Program Data
Note the following:
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BOOL arrays can be used as parameters to an instruction instead of variables of other data
types. The array must be of sufficient length to replace the given data type. For example,
instead of using a 16-bit INT variable, you could use a BOOL array of length 16 or more.
The following conditions must be met:
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Word-for-Word Changes

7.11
Many changes to the program that do not modify the size of the program are considered
word-for-word changes. Examples include changing the type of contact or coil, or changing a
reference address used for an existing function block.
Symbolic Variables
Creating, deleting, or modifying a symbolic variable definition is not a word-for-word change.
The following are word-for-word changes:
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Indirect references, which are available for all WORD-oriented memories (%R, %W, %P,
%L, %AI, %AQ), can be used as arguments to instructions wherever located variables in
the corresponding WORD-oriented memory are allowed. Note that indirect references are
converted into their corresponding direct references immediately before they are passed
into an instruction or function.
Bit-in-word references are generally allowed on contact and coil instructions other than
transition contacts and coils. They are also allowed as arguments to function parameters
that accept single or unaligned bits.
The BOOL array must be byte-aligned, that is, the reference address of the first element
of the BOOL array must be 8n + 1, where n = 0, 1, 2, 3, and so on. For example,
%M00033 is byte-aligned, because 33 = (8 × 4) + 1.
The parameter in question must support discrete memory reference addresses.
The instruction in question must not have a Length parameter. (The Length parameter is
displayed as ?? in the LD editor until a value is assigned.)
The data type to be replaced with a BOOL array must be one of the following:
Excess bits are ignored. For example, if you use a BOOL array of length 12 instead of an
8-bit BYTE, the last four bits of the BOOL array are ignored.
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Switching between two symbolic variables
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Switching between an symbolic variable and a mapped variable
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Switching between a constant and a symbolic variable
PACSystems* RXi Distributed IO Controller User Manual
Data Type Minimum Length
BYTE 8
INT, UINT, WORD 16
DINT, DWORD, REAL 32
REAL 64
GFK-2816F