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Chapter 4
Signal Connections
Motion Axis Signals
The following signals control the stepper driver:
•
Axis <1..4> Step (CW) and Dir (CCW)—These open-collector signals are the stepper
command outputs for each axis. The NI 7330 motion controller supports both major
industry standards for stepper command signals: step and direction, or independent CW and
CCW pulse outputs.
The output configuration and signal polarity is software programmable for compatibility
with various third-party drives, as follows:
–
When step and direction mode is configured, each commanded step (or microstep)
produces a pulse on the step output. The direction output signal level indicates the
command direction of motion, either forward or reverse.
–
CW and CCW mode produces pulses (steps) on the CW output for
forward-commanded motion and pulses on the CCW output for reverse-commanded
motion.
In either case, you can set the active polarity of both outputs to active-low (inverting) or
active-high (non-inverting). For example, with step and direction, you can make a logic
high correspond to either forward or reverse direction.
The Step (CW) and Dir (CCW) outputs are driven by high-speed open-collector TTL
buffers that feature 64 mA sink current capability and built-in 3.3 k
Ω
pull-up resistors to
+5 V.
Caution
Do
not
connect these outputs to anything other than a +5 V circuit. The
output buffers will fail if subjected to voltages in excess of +5.5 V.
•
Axis <1..4> Inhibit—Use the inhibit output signals to control the enable/inhibit function of
a stepper driver. When properly connected and configured, the inhibit function causes the
connected motor to be de-energized and its shaft turns freely. These open-collector inhibit
signals feature 64 mA current sink capability with built-in 3.3 k
Ω
pull-up resistors to +5 V,
and can directly drive most driver/amplifier inhibit input circuits.
While the industry standard for inhibits is active-low (inverting), these outputs have
programmable polarity and can be set to active-high (non-inverting) for increased
flexibility and unique drive compatibility.
Inhibit output signals can be activated automatically upon a shutdown condition, a Kill
Motion command, or any motion error that causes a kill motion condition, such as
following error trip. You can also directly control the inhibit output signals to enable or
disable a driver or amplifier.
Step, Direction, and Inhibit Output Circuit
The NI 7340 motion controller provides single-ended step, direction, and inhibit output signals.
To connect the NI 7340 to drives with opto-isolated inputs, connect as shown in Figure 4-2. If
the optocoupler does not include its own current-limiting resistor, you must provide an external
resistor in series with the NI 7340 output, as shown.
