National Instruments 653X Manuale Utente

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The polarity (whether to trigger on data that matches or mismatches 
the specified pattern)

For example, if you want to start acquisition when the two least significant 
bits of your data are 1 and 0, you would specify your trigger parameters to 
match those in Figure 2-11.

Figure 2-11.  Pattern-Matching Trigger Example

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.

You can transfer data continuously into or from computer memory or 
specify the number of points you want to transfer.

For finite transfers, the 653X device transfers the specified amount of data 
to/from computer memory and stops the operation.

For continuous input, the 653X 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 

X

X

X

X

X

X

1

0

0

0

0

0

0

0

1

1

Postive: Search for Match

Pattern to Detect

Mask

Polarity