National Instruments 636 Series

© National Instruments | 7-47
X Series User Manual
100 MHz Source Mode
In 100 MHz source mode, the device synchronizes signals on the rising edge of the source, and
counts on the third rising edge of the source. Edges are pipelined so no counts are lost, as shown
in Figure 7-40.
Figure 7-40. 100 MHz Source Mode
External Source Greater than 25 MHz
With an external source greater than 25 MHz, the device synchronizes signals on the rising edge
of the source, and counts on the third rising edge of the source. Edges are pipelined so no counts
are lost, as shown in Figure 7-41.
Figure 7-41. External Source Greater than 25 MHz
External or Internal Source Less than 25 MHz
With an external or internal source less than 25 MHz, the device generates a delayed Source
signal by delaying the Source signal by several nanoseconds. The device synchronizes signals
on the rising edge of the delayed Source signal, and counts on the following rising edge of the
source, as shown in Figure 7-42.
Figure 7-42. External or Internal Source Less than 25 MHz
100 MHz Source
Synchronize Count
External Source >25 MHz
Synchronize Count
Source
Delayed Source
Synchronize
Count