Watlow LogicPro - Manual (Page 132)

Chapter 10: Function Blocks LogicPro User’s Guide
116 Watlow Anafaze Doc.# 28002-00 Rev 3.00
Counter Up (CTU)
The Counter Up function block shown in Figure 10.1, enables
an output after a preset number of transitions from False to
True occur.
The CTU block increments the integer current value (CV) for
every False to True transition of the counter up enable bit
(CU). The current value continues to increment until it reaches
the integer preset value (PV). At that point, the output bit (Q)
is enabled and remains enabled until the function block is
reset by a True condition of the reset bit (R). While the reset
bit is True, the current value resets and remains at zero.
Figure 10.1 Counter Up Function Block
Inputs
CU is the Counter Up enable bit. As long as the reset bit is
False, each False to True transition of this bit increments the
current value until the current value equals the preset value. In
a program using Ladder logic, the value of CU is determined
by the Boolean evaluation of elements placed between the left
power rail and CU in the function block. I
n FBD p rograms, the
value of CU is determined by the Variable connected to CU. If
no contacts are placed on the rung before CU, the value of CU
is always True, but a transition never occurs.
R is the counter up reset bit. When this bit is True, the current
value is set to zero and the output bit is disabled. The value of
R is determined by the Boolean evaluation of elements placed
between the left power rail and R in the function block. If no
connection is made between the left power rail and R, the
value of R is always False.
PV is the counter up preset value. In Ladder logic, assign this
input a symbolic name or constant value in the
Assign
Function Block Symbolic Input/Output dialog box. In
FBD, assi gn a variable to this input in the Variable
Assignment dialog box. The range of values this Variable
can assume is from 1 to 32,767 for INT type Variables and 1
to 2,147,483,647 for LONG type Variables. If this Variable is
assigned a value out of these ranges, unpredictable results will
occur.