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Comparison instructions
F373_DTR
The function detects changes in a value at input s by comparing it with its former value that is
Description
stored at output d. If the new input value at s does not coincide with the old value, the function
assigns the new value to output d. To signal the change, the carry flag R9009 is set
simultaneously.
This instruction also exists as a P instruction (for FP2/2SH, FP3/5, FP10/10SH PLC types), which
is only executed at the rising edge of the EN trigger. Select [Insert P instruction] from the
"Instructions" pane if you require a P instruction. To facilitate reuse, the instruction then appears
under "Recently used" in the pop-up menu. Press <Ctrl>+<Shift>+<v> within the programming
area to open the list of recently used elements.
Availability of F373_DTR (see page 1325)
PLC types
The status of the carry flag is updated at each execution of the instruction.
Therefore, programs that use the carry flag should utilize it immediately after
F373_DTR is executed.
Data types
Variable
Data type
s
ANY16
d
Operands
For
s
d
Error flags
No.
IEC address
%MX0.900.9
R9009
In this example, the same POU header is used for all programming languages. For an example
Example
using IL (instruction list), please refer to the online help.
POU header
All input and output variables used for programming this function have been declared in the POU
header.
Body
When the variable start is set to TRUE, the function is carried out. If the input value present_value
has changed in comparison to the output value old_value the carry flag R9009 is set. The status of
the carry flag is then assigned to the variable changed_value.
616
16-bit data revision detection
Function
16-bit area for detecting data changes
area where data of previous execution is stored.
Relay
WX
WY
WR
WL
SV
-
WY
WR
WL
SV
Set
to TRUE
T/C
Register
EV
DT
LD
FL
EV
DT
LD
FL
If
the input value at s has changed in
comparison to the former value.
Constant
-
-
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