Rockwell-automation 1746-BAS BASIC LANGUAGE User Manual download pdf (Page 31)

Publication 1746-RM001A-US-P

Expressions and Operators 3-9

Comments on Trigonometric Functions

The SIN, COS, and TAN operators use a Taylor series to calculate the function.

These operators first reduce the argument to a value between 0 and PI/2. This

reduction is accomplished by the following equation:

reduced argument=(user arg/PI – INT(user arg/PI) *PI

The reduced argument, from the above equation, is between 0 and PI. The reduced

argument is then tested to see if is greater than

PI/2. If it is, then it is subtracted

from

PI to yield the final value. If it is not, then the reduced argument is the final

value.

Although this method of angle reduction provides a simple and economical means

of generating the appropriate arguments for a Taylor series, there is an accuracy

problem associated with this technique. The accuracy problem is noticed when the

user argument is large (example:

greater than 1000). This is because significant

digits in the decimal (fraction) portion of the reduced argument are lost in the

(user arg/PI - INT (user arg/PI)) expression. As a general rule, keep the

arguments for the trigonometric functions as small as possible.

Functional Operators

The module contains a complete set of functional operators. These operators are

single-operand operators.

ABS([expr])

Use the ABS operator to return the absolute value of the expression.

NOT([expr])

Use the NOT operator to return a 16-bit one’s complement of the expression. The

expression must be a valid integer (example:

between 0 and 65535 (0FFFFH)

inclusive

). Non-integers are truncated, not rounded.

Example Result

>PRINT ABS(5) 5

>PRINT ABS(–5) 5

Example Result

>PRINT NOT(65000) 535

>PRINT NOT(0) 65535

1 2 ... 26 27 28 29 30 31 32 33 34 35 36 ... 279 280

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Rockwell-automation 1746-BAS BASIC LANGUAGE User Manual Page 31