Chapter5 SignalConnections
7344/7334Hardware User Manual 5-4 ni.com
Motion Axis Signals
The following signals control the servo amplifier or stepper driver:
•Analog Output <1..4> (7344 only)—These 16-bit DACoutputs are
typically the servocommand outputs for each axis. They can drive
the industry-standard ±10 V output, and can be software limited to
anyp ositive or negative voltage range desired. They also feature
asoftware-programmable voltage offset.
Although typically used as the command output of an axis control
loop, unused DACscan also function as independent analog outputs
for general-purpose control.
•Analog Output Ground (7344 only)—Tohelp keep digital noise
separate from the analog DACoutputs, there is a separate return
connection. Youshould use this analog ground connection and not
DigitalG round (digitalI/O reference) as the reference for the DAC
outputs when connecting to servoampli fiers.
•Axis<1..4> Step (CW) and Dir (CCW)—These open-collector signals
are the stepper command outputs for each axis. The 7344/7334
controller supports both major industry standards for stepper
command signals—stepand di rection, or independent CW and CCW
pulse outputs.
Theoutput configuration and signal polarity is software programmable
for compatibility with various third-party drives,as follows:
–When step and directionm odeis configured, each commanded
step(or microstep) produces a pulse on the step output. The
direction output signal levelindicates the command d irection of
motion,either forward or reverse.
–CWand CCW mode produces pulses (steps) on the CW output for
forward-commandedmotion and pulses on the CCW output for
reverse-commandedmotion.
In eithercase, you can set the active polarity of both outputs to
active-low(inverting) or active-high (non-inverting). Forexample,
withstep and direction, you can make a logic high correspond to either
forwardor reverse direction.
TheStep(CW)andDir(CCW)outputsaredrivenbyhigh-speed
open-collectorTTL buffers that feature 64 mA sink current capability
andbuilt-in3.3kΩpull-upresistor sto +5 V.
Caution Do not connect these outputs to anything other than a +5 V circuit. The output
bufferswill fail if subjected to voltages in excess of +5.5 V.