Detect and Recover with

Digital I/O Watchdogs

Digital I/O watchdogs are an innovative technology that can detect a

variety of fault conditions such as an application crash and automatically

respond by setting the outputs to a user-configured safe state. Watchdogs

are important whenever the module is connected to actuators such as

pumps, valves, motors, and relays. A USB-6509 monitors the software

application; if the application fails to respond within a preset time limit,

the device automatically sets the output lines to a user-defined safe state.

A USB-6509 remains in the watchdog state until the watchdog timer is

disarmed, the device is reset, or the computer is restarted.

Trigger Your Application with

Change Detection

With change detection, you can automatically trigger your software

application to perform a digital read operation upon a digital change

of state. A digital change of state is defined as the rising edge (0 to 1

transition) or falling edge (1 to 0 transition) on one or more digital lines.

Using change detection, you can monitor for digital events with minimal

processor usage. No polling is necessary because the digital I/O module

generates an interrupt to automatically wake up your application.

Using NI-DAQmx software technology, the USB-6509 notifies the

software application when it detects an event, causing the application to

automatically perform a read operation. To minimize the effects of noisy

input lines, use programmable input filters in combination with change

detection to eliminate spurious change-detection events caused by noise

or glitches.

Eliminate Noise with Programmable

Input Filters

Programmable input filters remove noise, glitches, and spikes on

inputs as well as provide debouncing for digital switches and relays.

These features are important for applications in industrial environments

to prevent false readings caused by noise. You can configure the

programmable input filter for each digital line by setting the filter time.

The USB-6509 blocks any digital noise, glitch, or spike that is shorter

than half of the specified filter time, preventing invalid readings and

false triggers for change-detection events.

Recommended Software

National Instruments measurement services software, built around

NI-DAQmx driver software, includes intuitive application programming

interfaces, configuration tools, I/O assistants, and other tools designed

to reduce system setup, configuration, and development time. National

Instruments recommends using the latest version of NI-DAQmx driver

software for application development in NI LabVIEW, LabWindows/CVI,

and Measurement Studio. To obtain the latest version of NI-DAQmx, visit

speeds up your development with features including:

• A guide to create fast and accurate measurements with no

programming using the DAQ Assistant

• Free LabVIEW SignalExpress LE data-logging software

• Automatic code generation to create your application in LabVIEW;

LabWindows/CVI; LabVIEW SignalExpress; and Visual Studio .NET,

ANSI C/C++, C#, or Visual Basic 6.0

• Multithreaded technology for 1,000 times performance improvements

over basic DAQ driver software

• More than 3,000 free software downloads to jump-start your project

The USB-6509 is compatible with the following versions (or later) of

NI application software: LabVIEW, LabWindows/CVI, or Measurement

Studio versions 7.x; or LabVIEW SignalExpress 2.5. The USB-6509 is not

compatible with the Traditional NI-DAQ (Legacy) driver.

High-Density Industrial Digital I/O for USB – 96-Channel, 5 V TTL/CMOS

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BUY ONLINE at ni.com or CALL 800 813 3693 (U.S.)