Chapter 4
Signal Connections
4-14
ni.com
Trigger (Position Capture) Input Circuit
The PCI-7390 provides four optically isolated trigger inputs. Figure 4-9
shows a simplified schematic diagram of the circuit used by the trigger
inputs. Notice that the trigger inputs are sinking inputs. You can connect
the trigger input to a sourcing output device or a TTL driver. The polarity
of the trigger input is programmable in software as high level, low level,
rising edge, or falling edge. You also can use a trigger input as a latching
general-purpose digital input by simply ignoring the captured position.
Figure 4-9.
Trigger (Position Capture) Input Circuit
Caution
Excessive input voltages can cause erroneous operation and/or component
failure.
Breakpoint (Position Compare) Outputs
The PCI-7390 offers additional high-performance encoder features. The
encoder channels have position compare breakpoint outputs. This signal is
useful for high-speed synchronization of motion with actuators, sensors,
and other parts of the complete motion system:
•
Axis <1..4> Breakpoint Output
—You can program a breakpoint
output to transition when the associated encoder value equals the
breakpoint position. You can use a breakpoint output to directly control
actuators or as a trigger to synchronize data acquisition or other
functions in the motion control system.
You can program breakpoints as either
absolute
,
modulo
, or
relative
position. Breakpoint outputs can be preset to a known state so that the
transition when the breakpoint occurs can be low to high, high to low,
or toggle.
High Speed Optocoupler
V
cc
R
LIMIT
PCI-7390
Isolated
Ground
Trigger
Input
