Introduction

Chapter 5 Compare Instructions (CMP, EQU, GEQ, GRT, LEQ, LES, LIM, MEQ, NEQ)

Use Strings In an Expression

Use a relay ladder or structured text expression to compare string data types.

To use strings in an expression, follow these guidelines:

•

An expression lets you compare two string tags.

•

You cannot enter ASCII characters directly into the expression.

•

Only the following operators are permitted

>

>=

<>

Operator

=

<

<=

Description

equal less than less than or equal greater than greater than or equal not equal

•

Strings are equal if their characters match.

•

ASCII characters are case sensitive. Upper case “A” ($41) is not equal to lower case “a” ($61).

•

The hexadecimal values of the characters determine if one string is less than or greater than another string. For the hex code of a character, see the back cover of this manual.

•

When the two strings are sorted as in a telephone directory, the order of the strings determines which one is greater. s e r e s l e r a t g r e

AB

B a ab

ASCII Characters Hex Codes

1ab

1b

A

$31$61$62

$31$62

$41

$41$42

$42

$61

$61$62

AB < B a > B

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Publication 1756-RM003K-EN-P - July 2008

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