GE PACSystems RXi User Manual
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Chapter 7. CPU Program Data142 PACSystems* RXi Distributed IO Controller User Manual GFK-2816FNote the following:■ 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 inthe corresponding WORD-oriented memory are allowed. Note that indirect references areconverted into their corresponding direct references immediately before they are passedinto an instruction or function.■ Bit-in-word references are generally allowed on contact and coil instructions other thantransition contacts and coils. They are also allowed as arguments to function parametersthat accept single or unaligned bits.BOOL arrays can be used as parameters to an instruction instead of variables of other datatypes. 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: The BOOL array must be byte-aligned, that is, the reference address of the first elementof 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 isdisplayed 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:Data Type Minimum LengthBYTE 8INT, UINT, WORD 16DINT, DWORD, REAL 32REAL 64 Excess bits are ignored. For example, if you use a BOOL array of length 12 instead of an8-bit BYTE, the last four bits of the BOOL array are ignored.7.11 Word-for-Word ChangesMany changes to the program that do not modify the size of the program are consideredword-for-word changes. Examples include changing the type of contact or coil, or changing areference address used for an existing function block.Symbolic VariablesCreating, deleting, or modifying a symbolic variable definition is not a word-for-word change.The following are word-for-word changes:■ Switching between two symbolic variables■ Switching between an symbolic variable and a mapped variable■ Switching between a constant and a symbolic variable |
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