Chapter 3 Hardware Overview
National Instruments Corporation 3-21 AT-MIO/AI E Series User Manual
You can also individually enable each of the PFI pins to output a
specific internal timing signal. For example, if you need the 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 functions performed by the AT E Series boards 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.
An AT E Series board 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. You
select this timebase through software.
RTSI Triggers
The seven RTSI trigger lines on the RTSI bus provide a very flexible
interconnection scheme for any AT 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 3-15.