Operation
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Overview of input/output signals (I/Q)
Functions of the input/output signals
Switching the CPU from HALT
l
RUN enables the counter: The
incoming pulses are counted.
SetRefValue (Reset)
A rising edge 0
l
1 at the input overwrites the actual value with
the value present at the RefValue input.
Counter (actual value)
The counter actual value is provided at the Counter input.
Zero
If the actual value reaches the value 0, the Zero output is set. It
remains set until it is acknowledged by a 0
l
1 edge at the
QuitZero input.
RefWindowMode (activate reference window)
You can use this signal to define whether the signal for setting the
reference window is sent via input I4 or via the user program with
the SetRefWindow signal.
RefMode (type of referencing)
The signal at the input determines whether referencing is carried
out once (0 at input) or permanently (1 at input). The actual value
is overwritten with the reference value if the reference window is
set and a reference pulse is present at input I3. This is carried out
once (if the conditions are present after the controller is started) or
permanently (with every reference pulse in the reference window
depending on the setting for the RefMode signal).
Referencing
In many positioning controllers, a reference point is approached at
the start of positioning. For example, a tool slide is moved to its
home position. In this position, a reference switch is closed, thus
sending a signal to input I4. This can also be done by the
SetRefWindow signal which can be activated in the user program.
The RefActive signal is set as a feedback signal. An incremental
encoder connected to the slide generates a reference pulse to
specify the tool position exactly. This is detected at input I3 if the
reference switch is closed and the reference window is opened.
The reference pulse causes the counter to be overwritten with the
reference value that you have defined in the PLC configuration.
RefActive is reset and RefDone is set until the reference window is
opened again.
Figure 46: Input/output signals of the incremental value counter
RefDone
RefActive
Zero
Counter
QuitZero
RefMode
RefWindowMode
SetRefWindow
SetRefValue
RefValue
CPU
Signal A
l1
l2
l3
l4
Signal B
Reference
Signal
Reference
Window
Program
symbolic
addresses
Input
Incremental
encoder
Reference
switch
h
Set the reference window large enough for the reference
signal to be present only once and still be evaluated
reliably.
Figure 47: Relationship between reference signal and reference
window
T1 Pulse repetition time of two successive reference pulses with one
rotation of the incremental encoder
T2 Maximum permissible duration of the reference window. Must be
sufficiently less than T1 to ensure that a second marker pulse is not
detected.
T3 Must be long enough to ensure that the L/H edge of the marker
pulse is safely detected.
T2 and T3 depend on the frequency of the reference pulse and must be
determined for each application by trial and error.
T1
T2
T3
Reference Signal
Reference Window
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