Rockwell-automation 1775-KA PLC-3 Communication Adapter Module User Ma Manual de usuario descargar pdf (Pagina 70)

Addressing Rules and Examples

Chapter 4

414

Operator

Order of

ExecutionOperation

.LT.

Compare less than

.LE.

Compare less or equal

.NE.

Compare not equal

.AND.

Logical AND

.OR.

Logical OR

The result of an expression depends on the order in which the operators

are executed. The order of execution depends on the type of operator and

on left– to–right placement within the expression. Table 4.B gives the

order of execution for the different operators. For example, the command

$B67:45 = 6+3*2

would store the value 12 in word 45 of binary file 67. This is because

multiplication is performed before addition.

If an expression contains several operators with the same order of

execution, those operators will be executed in the left–to–right order in

which they appear within the expression. Extra set of parentheses can be

nested within each other to change the order of execution. In such cases,

the expression within the inner–most set of parentheses is evaluated first.

For example, the command

$B67:45=36%((6+3)*2)

would store the value 2 in word 45 of binary file 67 (% is the operator for

division).

Expressions can be used anywhere that direct numeric values can be used

within a message procedure, including within an address field. For

example, in the statement

$B67:(WORD+3)=5

the expression (WORD+3) specifies the address of a word within binary

file 67. Note that the parentheses are necessary to indicate that +3 is part

of the word address in this case.

1 2 ... 65 66 67 68 69 70 71 72 73 74 75 ... 238 239

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Rockwell-automation 1775-KA PLC-3 Communication Adapter Module User Ma Manual de usuario Pagina 70