NI 6520/6521 User Guide
8
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In periods A and B, the filter blocks the glitches because the external signal
does not remain steadily high from one rising edge of the filter clock to the
next. In period C, the filter passes the transition because the external signal
remains steadily high. Depending on when the transition occurs, the filter
may require up to two filter clocks—one full filter interval—to pass a
transition. Figure 2 shows a rising (0 to 1) transition. The same filtering
applies to falling (1 to 0) transitions.
Programmable Power-Up States
The default power-up state for Form C relays is deenergized (control bit is
low), which makes the contact connect at COM and NC. The Form C relay
status is user-configurable. If the power-up state of a Form C relay is
configured to energized (control bit is high), the contact connects at COM
and NO after power-up.
Figure 3.
Programmable Power-Up States for Form C Relays
The default power-up state for Form A relays is deenergized (control bit is
low), which makes the contact open at COM and NO. The Form A relay
status is user-configurable. If the power-up state of a Form A relay is
configured to energized (control bit is high), the contact connects at COM
and NO after power-up.
Figure 4.
Programmable Power-Up States for Form A Relays
User-configurable power-up states are useful for ensuring that the
NI 6520/6521 power up in a known state.
To use MAX (recommended) to program the power-up states, select
the device and click the
Properties
button. Refer to the software
documentation for information about how to program the power-up states
using NI-DAQ with LabVIEW or other National Instruments application
development environments (ADEs).
Note
The response time of programmable power-up states is 400 ms.
NC
NO
COM
NC
NO
COM
Control Bit Is High (1)
Control Bit Is Low (0)
NO
COM
NO
COM
Control Bit Is High (1)
Control Bit Is Low (0)