Rockwell Automation Logix5000 Controllers Structured Text Programming Manual - Manual (Page 17)

Publication 1756-PM007D-EN-P - November 2012 17
Program Structured Text Chapter 1
For example:
How Strings Are Evaluated
The hexadecimal values of the ASCII characters determine if one string is less
than or greater than another string.
• When the two strings are sorted as in a telephone directory, the order of
the strings determines which one is greater.
• Strings are equal if their characters match.
• Characters are case sensitive. Upper case “A” ($41) is not equal to lower
case “a” ($61).
Use this format Example
For this situation You’d write
value1 operator value2 If temp is a DINT tag and your specification
says: “If temp is less than 100
⋅
then…”
IF temp<100 THEN...
stringtag1 operator stringtag2 If bar_code and dest are string tags and your
specification says: “If bar_code equals dest
then…” IF bar_code=dest THEN...
char1 operator char2
To enter an ASCII character directly into
the expression, enter the decimal value of
the character.
If bar_code is a string tag and your
specification says: “If bar_code.DATA[0] equals
’A’ then…” IF bar_code.DATA[0]=65 THEN...
bool_tag := bool_expressions If count and length are DINT tags, done is a
BOOL tag, and your specification says ”If count
is greater than or equal to length, you are done
counting.” done := (count >= length);
ASCII Characters Hex Codes
1ab $31$61$62
1b $31$62
A $41
AB $41$42
B $42
a $61
ab $61$62
g
r
e
a
t
e
r
l
e
s
s
e
r
AB < B
a > B