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Chapter 4
Functional Overview
Embedded Real-Time Operating System (RTOS)
Trajectory Generators
Analog Feedback
NI PCI-7342 Hardware User Manual
The embedded firmware is based upon an embedded RTOS kernel and
provides optimum system performance in varying motion applications.
Motion tasks are prioritized, and task execution order depends on the
priority of each task, the state of the entire motion system, I/O or other
system events, and the real-time clock.
The DSP chip is a separate processor that operates independently from
the CPU but is closely synchronized by an internal packet-based command,
data, and messaging event structure. The PCI-7342 controller is a true
multiprocessing and multitasking embedded controller.
The advanced architecture of the PCI-7342 controller enables advanced
motion features, such as enhanced PID functions. Refer to the NI-Motion
Software Reference Manual for more information about the features
available on the PCI-7342 controller.
The trajectory generators on the PCI-7342 controller calculate the
instantaneous position command that controls acceleration and velocity
while moving the axis to its target position. Depending on how you
configure the axis, this command is sent to the PID servo loop or stepper
pulse generator.
To implement infinite trajectory control, the PCI-7342 controller has
four trajectory generators (two per axis) implemented in the DSP chip.
Each generator calculates an instantaneous position each PID update
period. While simple point-to-point moves require only one trajectory
generator, blended moves and infinite trajectory control processing require
two simultaneous generators.
The PCI-7342 controller has two multiplexed, 12-bit ADC channels
available for analog feedback. The converted analog values transmit to
both the DSP and CPU through a dedicated internal high-speed serial bus.
The multiplexer scan rate is approximately 50 µs per enabled ADC channel,
which provides the high sampling rates required for feedback loop closure,
joystick inputs, and monitoring analog sensors.
4-2
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