2-10
Functional Description
clock also allows you to synchronize conversions on multiple boards
to a common timing source.
The external clock source is an externally applied TTL-compatible
signal, which you attach to the INT_IN / XCLK pin (pin 24) of the
main I/O connector. When you start an analog input operation,
conversions are armed. At the next falling edge of the external clock
source (and at every subsequent falling edge of the external clock
source), a conversion is initiated.
Note:
If you are using a hardware external clock source, you cannot
use the INT_IN / XCLK pin (pin 24) to generate interrupts.
Figure 2-3 illustrates how conversions are initiated when using an internal
and an external clock source. (Note that Figure 2-3 assumes that you are
not using a hardware trigger; refer to Figure 2-4 for an illustration of
conversions when using a hardware trigger.)
Figure 2-3. Initiating Conversions
Operation is started
Conversions begin
when using an
external clock source
Conversions begin
when using an
internal clock source
External Clock
Source
Internal Clock
Source
(idle state)
count
count
count
count
