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National Instruments Corporation
5
USB-6525 User Guide and Specifications
Signal Descriptions
Table 2 describes the signals available on the I/O connectors.
Features
The NI 6525 features digital filtering, change detection, programmable
power-up output states, and a watchdog timer.
Digital Filtering
Use the digital filter option available on the NI 6525 input lines to eliminate
glitches on input data. When used with change detection, filtering can also
reduce the number of changes to examine and process.
You can configure the digital input channels to pass through a digital filter,
and you can program the filter interval the filter uses. The filter blocks
pulses that are shorter than half of the specified filter interval and passes
pulses that are longer than the specified interval. Intermediate-length
pulses—pulses longer than half of the interval but less than the
interval—may or may not pass the filter.
The filter operates on the inputs from the optocouplers. The optocouplers
turn on faster than they turn off, passing rising edges faster than falling
Table 2.
Signal Descriptions
Signal Name
Direction
Description
P0.<0..7>A/B
Output
Solid-state relay 60 VDC/30 V
rms
(42.4 V
pk
) output
P1.<0..6>+/–
Input
±60 VDC digital input.
P1.<0..6>+ corresponds to the positive input terminal.
P1.<0..6>– corresponds to the negative input terminal.
P1.7+/– or PFI 0+/–
Input
This channel is configurable as either a digital input or
an event counter.
Digital Input Signal
—±60 VDC digital input.
P1.7+ corresponds to the positive input terminal.
P1.7– corresponds to the negative input terminal.
CTR
—As a counter, this signal can be used as an event
counter input source.
PFI 0+ corresponds to the positive counter terminal.
PFI 0– corresponds to the negative counter terminal.
