Chapter 2
Hardware Overview
©
National Instruments Corporation
2-9
Figure 2-4 shows a rising edge trigger and a low pulse with a quadrature
encoder delay and a microsecond width.
Figure 2-4.
Rising edge trigger and a low pulse with a quadrature encoder delay and
a microsecond width
Product Selection Port
The product selection port consists of a group of five isolated digital inputs
that the software running on the NI 8255R reads simultaneously. You can
program the NI 8255R to switch between up to 32 inspection sequences for
different parts on an assembly line.
Based on the input to the product selection port, you can configure the
application software to run the appropriate inspection sequence. For
example, an upstream NI 8255R programmed for part classification might
drive the product selection port of a downstream NI 8255R. Alternatively,
a PLC with information about which part is being inspected can drive the
product selection port of the NI 8255R.
Using ISO Input 5 as a Latch
You can configure the product selection port to use ISO Input 5 as a latch.
A rising edge on ISO Input 5 can latch the data into a data register on the
NI 8255R. Before each inspection, the software checks the status of the
product select inputs and reads the most recent value latched into the
register. If ISO Input 5 is not used as a latch, it can be used as an extra bit
of data.
Note
In Vision Builder AI, ISO Input 5 is always designated as a latch.
Phase A
Phase B
Width
Trigger
Low Pulse
Delay
