Chapter 2
Using Your 653X
2-30
ni.com
Figure 2-19.
Pattern-Detection Trigger Example
Tip
To prevent a transient data value during line switching from falsely causing a match,
set a valid pattern for at least 60 ns to guarantee detection. In addition, keep glitches to less
than 20 ns to guarantee rejection.
Choosing Continuous or Finite Data Transfer
You can acquire data continuously into or from computer memory or
specify the number of points you want to transfer.
Finite Transfers
For finite transfers, the 653
X
device inputs the specified amount of data to
a computer memory buffer and stops the operation.
Continuous Input
For continuous input, the 653
X
device transfers input data to the computer
memory buffer continuously. As the device is filling the buffer, call the
DIG_DB_Transfer
function or the DIO Read VI to retrieve the data. If at
any time the device runs out of space in the buffer, it stops the operation
and NI-DAQ returns an error.
You have the option to allow the device to continue when it runs out of
buffer space and overwrite data you have not yet read. You can specify this
through the oldDataStop parameter in the
DIG_DB_Config
function and
the Data Overwrite/Regenerate parameter in the Digital Buffer Control VI,
called by the DIO Start VI.
X
X
X
X
X
X
1
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
1
1
Postive: Search for Match
Value to Detect
Pattern
Mask
Polarity