© National Instruments
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4-9
NI 7330 User Manual and Specifications
Figure 4-5.
Encoder Input Circuit
Trigger Inputs, Shutdown Input, and Breakpoint Outputs
The NI 7330 motion controller offers additional high-performance features in the encoder
FPGA. The encoder channels have high-speed position capture trigger inputs and breakpoint
outputs. These signals are useful for high-speed synchronization of motion with actuators,
sensors, and other parts of the complete motion system:
•
Trigger Input <1..4>—When enabled, an active transition on a high-speed position capture
input causes instantaneous position capture (<100 ns latency) of the corresponding encoder
count value. You can use this high-speed position capture functionality for applications
ranging from simple position tagging of sensor data to complex camming systems with
advance/retard positioning and registration. An available NI 7330 motion controller
position mode is to move an axis Relative to Captured Position.
The polarity of the trigger input is programmable in software as active-low (inverting),
active-high (non-inverting), rising, or falling edge. You can also use a trigger input as a
latching general-purpose digital input by simply ignoring the captured position.
•
Shutdown Input—When enabled in software, the shutdown input signal can be used to kill
all motion by asserting the controller inhibits, setting the analog outputs to 0 V, and
stopping any stepper pulse generation. To activate shutdown, the signal must transition
from a low to a high state, or rising edge.
•
Breakpoint Output <1..4>—A breakpoint output can be programmed 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.
The breakpoint outputs are driven by open-collector TTL buffers that feature 64 mA sink
current capability and built in 3.3 k
Ω
pull-up resistors to +5 V.
You can directly set and reset breakpoint outputs to use them as general-purpose digital
outputs.
Note
Breakpoint outputs and trigger inputs require an encoder connection.
74FCT244
6
8
0
Ω
1/
8
W
From the extern
a
l connector
encoder inp
u
t pin
s
To the
qua
dr
a
t
u
re
decoder circ
u
it
DGND
Vcc
3
.
3
k
Ω
