Device Overview; Digital I/O; Prescaling - National Instruments PCI-6601 User Manual

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Device Overview

This chapter provides information about the functionality of NI 660x

devices.

The NI 660x devices have a 32-bit DIO port on PFI <0..31>. Digital I/O

consists of asynchronous reads and writes to the digital port upon software

command. You can individually configure each line for digital input or

output. For output, you can individually configure PFI <8..31> for either

counter-associated output or digital output. You must specify whether you

are using the PFI line for counter I/O or digital I/O only if that line is being

used as an output. For input, both counter I/O and digital I/O can share the

lines on PFI <0..31>.

For more information about the signals that can be driven onto PFI lines,

refer to the

I/O Connector Pinout

For information about how to implement specific digital I/O functions,

refer to the application software documentation.

Prescaling allows the counter to count a signal that is faster than the

maximum timebase of the counter. The counters on the NI 660x devices

offer 8X and 2X prescaling on each counter (prescaling can be disabled).

Each prescaler consists of a small, simple counter that counts to eight

(or two) and rolls over. This counter is specifically designed for this

application and can count signals that are faster than the general purpose

counters. The CtrnSource signal on the general purpose counter will be the

divided signal from the simple counter.

section of this document.

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NI 660x User Manual

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