User`s manual

Local Logic Tutorial

GFK-1742A Chapter 11 Local Logic Tutorial 11-3

The Local Logic Parser generates an error if the program attempts to write to a read only variable,

or attempts to read a write only variable.

In addition, Local Logic variables have a size attribute ranging from Boolean (1-bit) to double

integer (64-bits). The Local Logic Parser generates a warning message when a non-Boolean value

is assigned to a Boolean variable. The warning indicates that data may be lost, due to truncation,

when this assignment occurs. The user should note that double integer variables (64-bit) variables

may only be used as the destination of a multiply operation, or the numerator of a divide or

modulus operation.

Consult chapter 13 for additional information concerning Local Logic variables. Additionally, the

Local Logic Variables Table (LLVT) within VersaPro contains the information on the variables

size, type and Read/Write properties.

Operators

Local logic provides three classes of operators. The operators are arithmetic, relational, and bitwise

logical operators. An introduction to each operator follows. A more detailed discussion of the

operators is contained in Chapter 12.

Arithmetic Operators

Local Logic provides the user with the ability to perform basic arithmetic operations. The language

supports 32-bit integer operations and limited use of 64/32 bit operations where appropriate to

maintain precision. All arithmetic functions, except the ABS function, require two operands.

Local Logic supports addition, subtraction, multiplication, division, absolute value, and modulus

operations.

Example constructs are:

P010 := Commanded_Velocity_1 - P009; (* P010=Commanded Velocity Axis 1 – P009*)

The user should note that the following would be an invalid mathematical construct:

Commanded_Velocity_1 := P010 - P009; (* Commanded_Velocity_1=P010-P009*)

The reason this is invalid is that the mathematical expression is attempting to assign the result

(P010-P009) to Commanded_Velocity_1 which is a read-only variable.

Storing intermediate results into parameter registers provides the flexibility necessary to solve

complex mathematical expressions.

For example, the following construct is invalid since it contains more than one operation (Multiply

and Subtraction):

P005:= Torque_Limit_1 *( P001 – P010);

To achieve the same result, the user can enter the following:

P004:= P001 – P010;

P005:= Torque_Limit_1 * P004;