Chapter4 Usingthe 6527
©NationalInstruments Corporation 4-3 6527User Manual

Digital I/O Circuitry

You can use your 6527 board as follows:
•Output ports
–Write
–Read back
•Input ports
–Read
–Apply digital filtering (software programmable)
–Changedetection on selected lines (software programmable)
Table3-1, Port Functionality for 6527 Devices, contains a summary of
port functions.

Optical Isolation Circuitry

The 5211 optocouplers optically isolate the digital input ports of a
6527 device. Each optocoupler provides optical isolation for one
channelof input.
InfineonLH1546 solid-st ate relays provideisolation o nthe output.
One solid-staterelay is used for isolation at each channel of output.
Fordiagrams of the complete input and output circuitry,see Chapter 3,
Making Signal Connections.
Digital Filtering
You can eliminate glitches on input data by using the digital filter option
thatis available on all the input lines. When used with change notification,
filtering can also reduce the number of changes for you to examine
andprocess.
Youcan configure any of the digital input channels from the optocouplers
topass through a digital filter. You can also control the timing intervalthat
the filteruses. The filter blocks pulses shorter than hal f of the specified
timing interval,treating them as glitches. The filterpasses pulses l onger
thanthe specified interval. Intermediate-length pulses—pulses longer than
halfof the interval but less than the interval—may or may not pass the filter.