Siemens NAN 67 Series Wartungshandbuch PDF herunterladen (Seite 177)

13-5

Ladder Logic (LAD) for S7-300 and S7-400

C79000-G7076-C504-02

13.3 Compare Floating-Point Numbers

The Compare Floating-Point Numbers instruction triggers a comparison

operation. You can use this instruction like a normal contact. This instruction

compares inputs IN1 and IN2 according to the type of comparison you select

from the browser. Table 13-5 lists the valid comparisons.

If the comparison is true, the result of logic operation (RLO) of the function

is 1. Otherwise it is 0. There is no negation of the compare output, because

this logic can also be handled by the inverse compare function.

Table 13-5 Types of Comparisons for Floating-Point Numbers

Type of Comparison Symbols in Name at Top of Box

IN1 is equal to IN2. ==

IN1 is not equal to IN2. <>

IN1 is greater than IN2. >

IN1 is less than IN2. <

IN1 is greater than or equal to IN2. >=

IN1 is less than or equal to IN2. <=

Table 13-6 Compare Floating-Point Numbers: Box and Parameters (Example: less than)

LAD Box Parameter Data Type Memory Area Description

CMP

< R

IN1 REAL I, Q, M, D, L First value to compare

IN1

IN2

REAL

IQMDL

Second value to compare

IN2

REAL

econ

o compare

Status Word Bits

BR CC 1 CC 0 OV OS OR STA RLO FC

Write – x x x x x 1 x 1

I 0.1

Output Q 4.0 is set if the following

conditions exist:

S There is a signal state of 1 at

inputs I 0.0 and I 0.1

S And MD0 = MD4

S And there is a signal state of 1 at

input I 0.2

Q 4.0

CMP

== R

IN2MD4

IN1MD0

I 0.0 I 0.2

Comparison is true:

Figure 13-3 Compare Floating-Point Numbers

Description

Comparison Instructions

1 2 ... 172 173 174 175 176 177 178 179 180 181 182 ... 317 318

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