Chapter 2
Using Your NI 653X
2-32
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 continuously acquire data into or transfer data from computer
memory or specify the number of points you want to transfer.
Finite Transfers
For finite transfers, the NI 653
X
acquires the specified amount of data to a
computer memory buffer and stops the operation.
Continuous Input
For continuous input, the NI 653
X
continuously transfers input data to the
computer memory buffer. As the device fills 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 can allow the device to continue when it runs out of buffer space and
overwrite data you have not yet read. You can specify this though the
oldDataStop
parameter in the
DIG_DB_Config
function and the
data
overwrite/regen.
parameter in the Digital Buffer Control VI, called by the
DIO Start VI.
0
0
0
0
0
0
1
1
Postive: Search for Match
Mask
X
X
X
X
X
X
1
0
0
0
0
0
0
0
1
0
Value to Detect
Pattern
Polarity
