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Chapter 4
Signal Connections
Motion Axis Signals
The following signals control the servo amplifier or stepper driver.
•
Analog Output <1..4>—These 16-bit DAC outputs are typically the servo command
outputs for each axis. They can drive the industry-standard ±10 V output, and can be
software limited to any positive or negative voltage range. They also feature
a software-programmable voltage offset.
Although typically used as the command output of an axis control loop, unused DACs can
also function as independent analog outputs for general-purpose control.
•
Analog Output Ground—To help keep digital noise separate from the analog DAC outputs,
there is a separate return connection. Use this analog ground connection and not Digital
Ground (digital I/O reference) as the reference for the DAC outputs when connecting to
servo amplifiers.
•
Axis <1..4> Step (CW) and Dir (CCW)—These open-collector signals are the stepper
command outputs for each axis. The NI 7340 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 kΩ pull-up resistors to
+5 V.
Caution
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 servo amplifier or 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 kΩ
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.
4-4 | ni.com
Do not connect these outputs to anything other than a +5 V circuit. The
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