© National Instruments | 4-14Digital Input/Output and PFIThis chapter describes the digital input/output (DIO) and Programmable Function Interface(PFI) functionality available on the cDAQ chassis. Refer to the Digital Input/Output and PFIsections.Digital Input/OutputTo use digital I/O, insert a digital I/O C Series module into any slot on the cDAQ chassis. TheI/O specifications, such as number of lines, logic levels, update rate, and line direction, aredetermined by the type of C Series module used. For more information, refer to thedocumentation included with your C Series module(s).Serial DIO versus Parallel DIO ModulesSerial digital modules have more than eight lines of digital input/output. They can be used in anychassis slot and can perform the following tasks:• Software-timed and hardware-timed digital input/output tasksParallel digital modules can be used in any chassis 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 signalsSoftware-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 cDAQ chassis, go to ni.com/info and enter the Info Code rdcdaq.
