Serial Dio Versus Parallel Dio Modules; Static Dio; Digital Input - National Instruments cRIO-904 Series User Manual

Serial DIO versus Parallel DIO Modules

Serial digital modules have more than eight lines of digital input/output. They can be used in
any controller slot and can perform the following tasks:
• Software-timed and hardware-timed digital input/output tasks
Parallel digital modules can be used in any controller slot and can perform the following tasks:
• Software-timed and hardware-timed digital input/output tasks
• Counter/timer tasks (can be used in up to two slots)
• Accessing PFI signal tasks (can be used in up to two slots)
• Filter digital input signals
Software-timed and hardware-timed digital input/output tasks have the following restrictions:
• You cannot use parallel and serial modules together on the same hardware-timed task.
• You cannot use serial modules for triggering.
• You cannot do both static and timed tasks at the same time on a single serial module.
• You can only do hardware timing in one direction at a time on a serial bidirectional
module.
To determine the capability of digital modules supported by the controller, refer to the
Software Support for CompactRIO, CompactDAQ, Single-Board RIO, R Series, and EtherCAT
document by going to

Static DIO

Each of the DIO lines can be used as a static DI or DO line. You can use static DIO lines to
monitor or control digital signals on some C Series modules. Each DIO line can be
individually configured as a digital input (DI) or digital output (DO), if the C Series module
being used allows such configuration.
All samples of static DI lines and updates of static DO lines are software-timed.

Digital Input

You can acquire digital waveforms using either parallel or serial digital modules. The DI
waveform acquisition FIFO stores the digital samples. The cRIO controller samples the DIO
lines on each rising or falling edge of the DI Sample Clock signal.
Multiple input timing engines allow the cRIO controller to run up to eight hardware-timed
digital input tasks simultaneously, each using independent timing and triggering
configurations. The eight input timing engines are it0, it1,...it7. All eight of the input timing
engines are shared between analog input and digital input tasks, allowing up to 8 hardware-
timed input tasks.
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