Watlow LogicPro - Manual (Page 163)

LogicPro User’s Guide Chapter 10: Function Blocks
Doc.# 28002-00 Rev 3.00 Watlow Anafaze 147
Figure 10.27 Real Less Than Function Block
Inputs
EN is the Real Less Than enable bit. A True condition of this
bit causes the comparison between RA and RB to occur. In a
program using Ladder logic, the value of EN is determined by
the Boolean evaluation of elements placed between the left
power rail and EN in the function block. In FBD programs, the
value of EN is determined by the Variable connected to EN. If
no contacts are placed on the rung before EN, the value of EN
is always True. In FBD, all inputs must be connected to a
Variable.
RA is one comparison value. The range of values this Variable
can assume is from -3.4x10
38 to 3.4x10 38 . If this Variable is
assigned a value out of these ranges, unpredictable results will
occur.
RB is another comparison value. The range of values this
Variable can assume is from -3.4x10
38 to 3.4x10 38 . If this
Variable is assigned a value out of these ranges, unpredictable
results will occur.
Output
Q is the Real Less Than output bit. This bit is enabled and
passes power when the enable bit is True and the value of RA
is less than the value of RB.
Real Equal To (REQ)
The Real Equal To (REQ) function block, as shown in Figure
10.28 on page 148, tests if a real Variable value is equal to a
reference value.
REQ tests whether one value (RA) is equal to another value
(RB) when the enable bit (EN) is True. If the relationship
RA=RB is True, then the output bit (Q) is enabled. The output
bit is disabled either when the enable bit becomes False or the
value of RA is no longer equal to RB. The values of RA and RB
can be preset to a constant or assigned a symbolic name,