National-instruments PCI-6023E User Manual download pdf (Page 28)

Chapter 3 Hardware Overview

PCI-6023E/6024E/6025E User Manual 3-8

National Instruments Corporation

UPDATE* signal as an output on the I/O connector, software can turn on

the output driver for the PFI5/UPDATE* pin.

Board and RTSI Clocks

Many board functions require a frequency timebase to generate the

necessary timing signals for controlling A/D conversions, DAC updates, or

general-purpose signals at the I/O connector.

These boards can use either its internal 20 MHz timebase or a timebase

received over the RTSI bus. In addition, if you configure the board to use

the internal timebase, you can also program the board to drive its internal

timebase over the RTSI bus to another board that is programmed to receive

this timebase signal. This clock source, whether local or from the RTSI bus,

is used directly by the board as the primary frequency source. The default

configuration at startup is to use the internal timebase without driving the

RTSI bus timebase signal. This timebase is software selectable.

RTSI Triggers

The seven RTSI trigger lines on the RTSI bus provide a very flexible

interconnection scheme for any PCI E Series board sharing the RTSI bus.

These bidirectional lines can drive any of eight timing signals onto the

RTSI bus and can receive any of these timing signals. This signal

connection scheme is shown in Figure 3-4.

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National-instruments PCI-6023E User Manual Page 28