Справочник Пользователя для National Instruments NI VISION PCI-8254R

The NI 8254R is capable of detecting edges on various trigger lines and 
latching this information for future retrieval. This feature is useful for 
high-precision hardware-monitoring of the presence of external events 
without the need for software polling. You can arm for the detection of a 
rising edge, falling edge, or both on a supported trigger input line.

Supported trigger input lines include TTL Input 0, TTL Input 1, 
ISO Input 8, ISO Input 9, ISO Input 10, and TRIG 0.

The quadrature encoder uses ISO Input 6 for its Phase A input and 
ISO Input 7 for its Phase B input. Encoder speed is limited by the speed of 
the isolated inputs. Each isolated input can change at a maximum rate of 
100 kHz, making the maximum encoder rate 400,000 counts/s.

The quadrature encoder can also be used as a timebase for the pulse 
generation delay.

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 low pulse

The product selection port consists of a group of five isolated digital inputs 
that the software running on the NI 8254R reads simultaneously. You can 
program the NI 8254R to switch between up to 32 (2

5

) inspection 

sequences for different parts on an assembly line.

Phase A

Phase B

Delay

Width

Trigger

Low Pulse