National Instruments NI PCIe-8255R User Manual

Also see for NI PCIe-8255R: Quick start guide Getting started Quick start guide

National Instruments NI PCIe-8255R User Manual Manual pdf 17 page image

Chapter 2 Hardware Overview© National Instruments Corporation 2-5 NI PCIe-8255R User ManualI/O for Normal OperationThe following sections describe I/O functions that are available on theNI 8255R during normal operation.Trigger InputsTrigger inputs are available from both TTL inputs and isolated inputs. Youcan use these trigger inputs to synchronize the NI 8255R with an externalevent, such as the assertion of a signal generated by a proximity sensor ora PLC, to indicate that an inspection item is passing in front of the camera.The NI 8255R can use this input to initiate a timed pulse for camera control,lighting control, encoder pulse counting, and result output timing.For more information about creating a timed pulse output, refer to theTimed Pulse Output section.TTL Input 0, TTL Input 1, TRIG 0, ISO Input 6, ISO Input 7, ISO Input 8,and ISO Input 11 can alternatively function as general-purpose inputs.ISO Input 5 can alternatively function as a latch for the product selectionport.Timed Pulse OutputThe NI 8255R is capable of timed pulse output on six different digitaloutputs, which provides precise control over time-critical signals, such ascamera exposure. This section describes the various uses for the timedpulse output and the parameters you can set to control these outputs.Uses for timed pulse output include controlling camera reset and exposure,controlling strobe lighting, operating plungers on an assembly line, andcommunicating with PLCs. You can configure the start of the pulse outputgeneration to occur from software or from a rising or falling edge of atrigger input.In addition to controlling the timing of pulse output, you can also configurethe polarity of the output signal, resulting in a high-true or low-true signal.Based on the polarity setting, the output signal asserts after the appropriatedelay time and de-asserts after the configured pulse width. You can set thedelay time in microseconds or in quadrature encoder counts from the startsignal—either a hardware trigger or a software command. Width is alwaysconfigured in microseconds.