Watlow LogicPro - Manual (Page 166)

Chapter 10: Function Blocks LogicPro User’s Guide
150 Watlow Anafaze Doc.# 28002-00 Rev 3.00
RSUB calculates the difference between one value (RA) and
another value (RB) and places the result in another Variable
(RC) when the enable bit (EN) is True. The values of RA and
RB can be preset to a constant or assigned a Variable name,
which allows their value to change dynamically within the
program.
Figure 10.30 Real Subtract Function Block
Inputs
EN is the Real Subtract enable bit. A True condition of this bit
causes the value of RB to be subtracted from the value of RA
and the result stored in RC. 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 in a Ladder Diagram program,
the value of EN is always True. In FBD, all inputs must be
connected to a Variable.
RA is the value to be subtracted from. 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 the value to subtract. 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.
Outputs
ENO is the Real Subtract enable out bit. This bit is enabled and
passes power when the enable bit is True as long as the value
of RC does not go out of range.
RC is the subtract result value. RC contains the difference
between RA and RB, as long as the enable bit is True. 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, ENO is disabled. RC reverts to its last valid value
whenever ENO is disabled.