Configuring the Breakpoint Pulse Width (NI 7350 only)

On NI 7350 devices you can configure a customized pulse width for breakpoints (position compare outputs) to trigger devices that have specific minimum active pulse requirements. The default breakpoint pulse width is 200 ns. You can use MAX or the Write Capture Compare Data VI or function to set a pulse width of between 1 µs and 65,535 µs. On a breakpoint event, the breakpoint signal is active for the configured pulse width, as shown in the following figure.

Note  A breakpoint across RTSI always generates an active high pulse of 200 ns duration.

Caution  The breakpoint frequency depends on the velocity and distance between breakpoints and is limited by the pulse width. The breakpoint frequency must meet the following requirements for correct operation.

Breakpoint Frequency Requirements

The breakpoint pulse must not overlap with the next breakpoint event. If the breakpoint pulse overlaps with the next breakpoint event, breakpoint generation is stopped and the breakpoint is disabled. To recover from this situation change the pulse width, velocity, or distance between breakpoints. In addition, the breakpoint frequency cannot be greater than the maximum value allowed for the specified breakpoint type. Therefore, the breakpoint frequency, in hertz, at the specified pulse width, in seconds, must conform to must conform to the following two conditions:

AND

Position Compare (Breakpoint) Output Type	Maximum Frequency
Single	150 Hz
Buffered, PID rate of 62.5 µs to 250 µs	2 kHz
Buffered, PID rate greater than 250 µs	1 kHz
Periodic	4 MHz