National Instruments cRIO-904 Series User Manual

National Instruments cRIO-904 Series User Manual Manual pdf 77 page image

80 MHz Source ModeIn 80 MHz source mode, the controller synchronizes signals on the rising edge of the source,and counts on the third rising edge of the source. Edges are pipelined so no counts are lost, asshown in the figure below.Figure 48. 80 MHz Source Mode80 MHz SourceSynchronize CountExternal or Internal Source Less than 20 MHzWith an external or internal source less than 20 MHz, the module generates a delayed Sourcesignal by delaying the Source signal by several nanoseconds. The controller synchronizessignals on the rising edge of the delayed Source signal, and counts on the following risingedge of the source, as shown in the figure below.Figure 49. External or Internal Source Less than 20 MHzSourceDelayed SourceSynchronizeCountCounter Input ApplicationsThe following sections list the various counter input applications available on the cRIOcontroller:• Counting Edges• Pulse-Width Measurement• Pulse Measurement• Semi-Period Measurement• Frequency Measurement• Period Measurement• Position Measurement• Two-Signal Edge-Separation MeasurementCounting EdgesIn edge counting applications, the counter counts edges on its Source after the counter isarmed. You can configure the counter to count rising or falling edges on its Source input. YoucRIO-904x User Manual | © National Instruments | 77