National Instruments 778970-01 Digital I/O Device

National Instruments part number 778970-01 is an identifying part number for the PCI-6513, a Digital I/O Device. The device features a digital filter option for data lines to eliminate glitches on input data. When used with change detection, filtering can reduce the number of changes to examine and process. Users can configure the digital input filters to pass through a digital filter after the photocouplers and control the timing interval for the filter operations. The filter blocks pulses shorter than half of the specified timing interval, while pulses longer than the interval pass through. Pulses that are longer than half the interval but shorter than the full interval may or may not pass the filter.

This digital device is equipped with a 100-pin keyed female SCSI I/O connector, with a maximum input voltage of ±30 VDC and a maximum input current of 12.5 mA per line. The part number for the PCI-6513 Bundle is 778974-01. When the watchdog timer is enabled, if this device does not receive a reset command within the specified time, the outputs will shift to a user-defined safe state and remain there. This state persists until the application disarms the watchdog timer, new values are written, the device is reset, or the computer is restarted. The signal indicating an expired watchdog will continue to assert until the watchdog timer is disarmed. Once the watchdog timer expires, the NI 778970-01 Digital I/O device will ignore any writes until the timer is disarmed. Users can set the watchdog timer timeout period to determine the duration before the timer expires. 

The channel processes inputs from the photocouplers, which turn on faster than they turn off, passing rising edges more quickly than falling edges. Users can enable filtering on as many input lines as needed for their application. All filtered lines share the same timing interval, ranging from 200 μs to 200 ms. Internally, the filter uses two clocks: the sample clock and the filter clock. The sample clock on this device has a 100 ns period. The filter clock is generated by a counter and has a period equal to half of the specified timing interval. The input signal on the NI 778970-01 is sampled on each rising edge of the sample clock, which occurs every 100 ns. However, a change in the input signal is recognized only if it maintains its new state for at least two consecutive rising edges of the filter clock.