csmstr - Omega Engineering

MULTIPLE CONDITIONS
CRIMSON USER MANUAL - MODULAR CONTROLLER
OPERATOR PRIORITY EXAMPLE
Bit Selection Group 1 Input.2
The example shown tests bit 2 (ie. the bit with a value of 4) within the indicated tag.
If you want to test for a bit being equal to zero, you can use the logical NOT operator…
OPERATOR PRIORITY EXAMPLE
Logical NOT Group 2 !Input.2
This example is equal to 1 if bit 2 of the indicated tag is equal to 0, and vice versa.
MULTIPLE CONDITIONS
If you want to define an expression that is true if a number of conditions are all true, you can
use the logical AND operator. Similarly, if you want to define an expression that is true if any
of a number of conditions are true, you can use the logical OR operator. The examples below
show each operator in use…
OPERATOR PRIORITY EXAMPLE
Logical AND Group 11 A>10 && B>10
Logical OR Group 12 A>10 || B>10
The logical AND operator produces a value of 1 if and only if the expressions on the
left-hand and right-hand sides are true, while the logical OR operator produces a value of 1 if
either expression is true. Note that—unlike the bitwise operators referred to elsewhere in this
section—the logical operators stop evaluating once they know what the answer will be. This
means that in the above example for logical AND, the right-hand side of the operator will
only be evaluated if A is greater than 10, as, if this were not true, the result of the AND
operator must already be zero. While this property makes little difference in the examples
given above, if the left-hand or right-hand expressions call a program or make a change to a
data value, this behavior must be taken into account.
CHOOSING VALUES
You may find situations where you want to select between two values—be they integers,
floating-point values or strings—depending on the value of some condition. For example, you
may wish to set a motor’s speed equal to 500 rpm or 2000 rpm based on a flag tag. This
operation can be performed using the ?: operator, which is unique in that it takes three
arguments, as shown in the example below…
OPERATOR PRIORITY EXAMPLE
Selection Group 13 Fast ? 2000 : 500
This example will evaluate to 2000 if Fast is true, and 500 otherwise. The operator can be
thought to be equivalent to the IF function found in applications such as Microsoft Excel.
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