National Instruments 6527 - Manual (Page 32)

Chapter 4 Using the 6527
© National Instruments Corporation 4-3 6527 User 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)
– Change detection on selected lines (software programmable)
Table 3-1, 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
channel of input.
Infineon LH1546 solid-state relays provide isolation on the output.
One solid-state relay is used for isolation at each channel of output.
For diagrams 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
that is available on all the input lines. When used with change notification,
filtering can also reduce the number of changes for you to examine
and process.
You can configure any of the digital input channels from the optocouplers
to pass through a digital filter. You can also control the timing interval that
the filter uses. The filter blocks pulses shorter than half of the specified
timing interval, treating them as glitches. The filter passes pulses 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.