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Chapter 7 Counters
© National Instruments Corporation 7-39 NI 6238/6239 User Manual
Otherwise, the mode depends on the signal that drives Counter n Source.
Table 7-6 describes the conditions for each mode.
80 MHz Source Mode
In 80 MHz source mode, the device synchronizes signals on the rising edge
of the source, and counts on the following rising edge of the source, as
shown in Figure 7-34.
Figure 7-34. 80 MHz Source Mode
Other Internal Source Mode
In other internal source mode, the device synchronizes signals on the
falling edge of the source, and counts on the following rising edge of the
source, as shown in Figure 7-35.
Table 7-6. Synchronization Mode Conditions
Duplicate
Count
Prevention
Enabled
Type of
Measurement
Signal Driving
Counter n
Source
Synchronization
Mode
Yes Any Any 80 MHz Source
No Position
Measurement
Any 80 MHz Source
No Any 80 MHz
Timebase
80 MHz Source
No All Except
Position
Measurement
20 MHz
Timebase, 100
kHz Timebase,
or PXI_CLK10
Other Internal
Source
No All Except
Position
Measurement
Any Other
Signal (such as
PFI or RTSI)
External Source
Source
Synchronize Count