National Instruments PCI-6251 User Manual

© National Instruments | 7-35
M Series User Manual
Enabling Duplicate Count Prevention in NI-DAQmx
You can enable duplicate count prevention in NI-DAQmx by setting the Enable Duplicate
Count Prevention attribute/property. For specific information about finding the Enable
Duplicate Count Prevention attribute/property, refer to the help file for the API you are using.
Synchronization Modes
The 32-bit counter counts up or down synchronously with the Source signal. The Gate signal and
other counter inputs are asynchronous to the Source signal. So M Series devices synchronize
these signals before presenting them to the internal counter.
M Series devices use one of three synchronization methods:
•
80 MHz Source Mode
• Other Internal Source Mode
• External Source Mode
In DAQmx, the device uses 80 MHz source mode if you perform the following:
• Perform a position measurement
• Select duplicate count prevention
Otherwise, the mode depends on the signal that drives Counter n Source. Table 7-8 describes the
conditions for each mode.
Table 7-8. 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

National Instruments PCI-6251 Specifications

General

Brand	National Instruments
Model	PCI-6251
Category	I/O Systems
Language	English