Rockwell Automation GMLC Reference Manual - Manual (Page 510)

Publication GMLC-5.2 - November 1999
System Variables 473
Less Than or Equal to
<=
Use a less-than sign followed by an equal sign to determine if one element
or expression is equal to or less than another element or expression. If the
element or expression on the left side of the <= is equal to or has a lower
value than the element or expression on the right side, the comparison is
true (1). Otherwise it is false (0). For example, the following expression
has a value of 1 (true) if the current position of Axis 0 is equal to or less
than the cut length variable, and 0 (false) otherwise.
Actual_Position_AXIS0 <= Cut_Length
This result is exactly opposite from that obtained when >= is used.
System Variables
System variables appear in the Expression Builder’s Tag Explorer in two
groupings:
• Axis System Variables — Lets you use motion-related parameter
(position, velocity, etc.) and axis status values as elements in
expressions.
• General System Variables — Lets you use system operation and
communications status values as elements in expressions.
Important: Certain system variables depend on the configuration settings
made in the Configure Control Options dialog box. These
settings determine if they appear in the Tag Window.
To include a system variable in your expression open the Expression
Builder and select a system variable type from the Tag Explorer. You can
either select Axis System Variables or General System Variables. At the
Tag Window, scroll the list and select a variable. The selected variable
appears at the cursor position in the Expression = window. Now
Complete your expression using other Expression Builder features, and
select OK.