Rockwell-automation 1771-DB Basic Module User Manual - Series A Manual de usuario descargar pdf (Pagina 41)

Operating Functions

Chapter 5

5–4

Important: The BASIC Module requires less time to find a scalar

variable because there is no expression to evaluate. If you want to run a

program as fast as possible, use dimensioned variables only when

necessary. Use scalars for intermediate variables and assign the final

result to a dimensioned variable. Also, put the most frequently used

variables first. Variables defined first require the least amount of time

to locate.

An expression is a logical mathematical expression that involves

operators (both unary and dyadic), constants and variables. Expressions

are simple or complex, (e.g. 12*EXP(A)/100, H(1) + 55, or

(SIN(A)*SIN(A)+COS(A)* COS(A)/2). A “stand alone” variable [var]

or constant [const] is also considered an expression. We refer to

expressions as:

[expr].

Relational expressions involve the operators EQUAL (=), NOT

EQUAL (tu), GREATER THAN OR EQUAL TO (u=), and

LESS THAN OR EQUAL TO (t=). You use them in control statements

to test a condition (i.e. IF A t100 THEN...). Relational expressions

always require two operands. We refer to relational expressions as:

[rel expr].

The system control values include the following:

LEN (returns the length of your program).

MTOP (the last memory location assigned to BASIC).

See the following Section 5.6.2 titled, “System Control Values” for

more information.

5.2.8

Variables (continued)

5.2.9

Expressions

5.2.10

Relational Expressions

5.2.11

System Control Values

1 2 ... 36 37 38 39 40 41 42 43 44 45 46 ... 166 167

Sin comentarios

Rockwell-automation 1771-DB Basic Module User Manual - Series A Manual de usuario Pagina 41