Digital I/O Considerations for C Series Devices

Digital I/O module capabilities depend on the type of digital signals that the module can measure or generate. Static digital I/O modules are designed for signals that change slowly and are accessed by software-timed reads and writes. Static digital I/O modules might take longer to update than their specifications indicate. Correlated digital I/O modules are for signals that change rapidly and are updated by either software or hardware-timed reads and writes. In addition, correlated digital I/O modules can perform the following tasks:

• Hardware-timed digital input/output tasks (when used in slots 1 through 4)
• Counter/timer tasks (when used in slots 5 and 6)
• Accessing PFI signal tasks (when used in slots 5 and 6)

The NI 9403, NI 9425, NI 9476, and NI 9477 are static digital I/O modules. The NI 9401, NI 9402, NI 9411, NI 9421, NI 9422, NI 9423, NI 9435, NI 9472, NI 9474, NI 9481, and NI 9485 are correlated digital I/O modules.