PMAC Quick Reference Guide CLOSE ena PLC15 ; Enable the PLC (I5 must be 2 or 3) P1..10 ; List the values of P1 to P10 The same concept applies for Q-Variables and M-Variables arrays, although the address range for them is different. Operators PMAC operators work like those in any computer language: they combine values to produce new values. PMAC uses the four standard arithmetic operators: + , - , * , and / . The standard algebraic precedence rules are used: multiply and divide are executed before add and subtract, operations of equal precedence are executed left to right, and operations inside parentheses are executed first.
PMAC also has the % modulo operator, which produces the resulting remainder when the value in front of the operator is divided by the value after the operator. Values may be integer or floating point. This operator is useful particularly for dealing with counters and timers that roll over. When the modulo operation is done by a positive value X, the results can range from 0 to X (not including X itself). When the modulo operation is done by a negative value -X, the results can range from -X to X (not including X itself). This negative modulo operation is useful when a register can roll over in either direction. PMAC has three logical operators that do bit-by-bit operations:
& (bit-by-bit AND ), | (bit-by-bit OR ), and ^ (bit-by- bit EXCLUSIVE OR ). If floating-point numbers are used, the operation works on the fractional as well as the integer bits. & has the same precedence as * and / ; | and ^ have the same precedence as + and - . Use of parentheses can override the default precedence. Functions These perform mathematical operations on constants or expressions to yield new values. The general format is: {function name} ({expression}) The available functions are SIN , COS , TAN , ASIN , ACOS , ATAN , ATAN2 , SQRT , LN , EXP , ABS , and INT . The global I-Variable I15 controls whether the units for the trigonometric functions are degrees or radians.
36 Programming PMAC SIN This is the standard trigonometric sine function. COS This is the standard trigonometric cosine function. TAN This is the standard trigonometric tangent function. ASIN This is the inverse sine (arc-sine) function with its range reduced to +/-90 degrees. ACOS This is the inverse cosine (arc-cosine) function with its range reduced to 0 -- 180 degrees. ATAN This is the standard inverse tangent (arc-tangent) function. ATAN2 This is an expanded arctangent function, which returns the angle whose sine is the expression in parentheses and whose cosine is the value of Q0 for that coordinate system.
If doing the calculation in a PLC program, make sure that the proper coordinate system has been addressed in that PLC program. (Actually, it is only the ratio of the magnitudes of the two values, and their signs, that matter in this function). It is distinguished from the standard ATAN function by the use of two arguments. The advantage of this function is that it has a full 360-degree range, rather than the 180-degree range of the single-argument ATAN function. LN This is the natural logarithm function (log base e). EXP This is the exponentiation function (ex). Note: To implement the yx function, use ex ln(y) instead.
A sample PMAC expression would be EXP(P2*LN(P1)) to implement the function P1P2. SQRT This is the square root function. ABS This is the absolute value function. INT This is a truncation function, which returns the greatest integer less than or equal to the argument (INT(2.5)=2, INT(-2.5)=-3).