Watlow LogicPro - Manual (Page 155)

LogicPro User’s Guide Chapter 10: Function Blocks
Doc.# 28002-00 Rev 3.00 Watlow Anafaze 139
FBD programs, the value of UNLD is determined by the
Variable connected to UNLD. If no contacts are placed on the
rung before UNLD, the value of UNLD is always False. This bit
has higher evaluation priority than the LD bit in this function
block.
CLR is the LIFO clear bit. When this bit is True, the stack is
cleared of any values and the count Variable is set to zero. In
a Ladder Diagram program, the value of CLR is determined by
the Boolean evaluation of elements placed between the left
power rail and CLR in the function block. In FBD programs,
the value of CLR is determined by the Variable connected to
CLR. If no contacts are placed on the rung before CLR, the
value of CLR is always False. This bit takes the highest
evaluation priority of the input bits in this function block.
INP is the LIFO input Variable. In Ladder logic, assign this
input a symbolic name or constant value in the
Assign
Function Block Symbolic Input/Output dialog box. In
FBD, assign a variable to this input in the Variable
Assignment dialog box. The value of this Variable is placed
in the stack at the location of the count Variable. The range of
values this Variable can assume is from -32,768 to 32,767,
including 0 for INT type Variables and -2,147,483,648 to
2,147,483,647, including 0 for LONG type Variables. If this
Variable is assigned a value out of these ranges, unpredictable
results will occur.
SIZE is the LIFO size Variable. The value assigned to this
Variable determines the size of the stack. For this reason,
assign a constant value and do not change this value online.
This Variable should be either a positive integer or a constant.
Outputs
Q is the LIFO output bit. This bit is enabled and passes power
when a False to True transition of the unload bit occurs. This
bit remains enabled until there are no more values in the stack
to unload and the count Variable equals zero.
FUL is the LIFO full bit. This bit is enabled and passes power
when the count value is equal to the size value. A rung with an
output coil is not needed between FUL in the function block
and the right power rail (in a Ladder Diagram program) or
connect an output Variable to it (in a FBD program).
EMP is the LIFO empty bit. This bit is enabled and passes
power when the count value equals zero. A rung with an
output coil is not needed between EMP in the function block
and the right power rail (in a Ladder Diagram program) or
connect an output Variable to it (in a FBD program).