Chapter 4 Signal ConnectionsPCI-6110E/6111E User Manual4-32 ©National Instruments CorporationGPCTR1_SOURCE SignalAny PFI pin can externally input the GPCTR1_SOURCE signal, whichis available as an output on the PFI3/GPCTR1_SOURCE pin.As an input, the GPCTR1_SOURCE signal is configured in theedge-detection mode. You can select any PFI pin as the source forGPCTR1_SOURCE and configure the polarity selection for eitherrising or falling edge.As an output, the GPCTR1_SOURCE monitors the actual clockconnected to general-purpose counter 1. This is true even if the sourceclock is being externally generated by another PFI. This output is set totri-state at startup.Figure 4-29 shows the timing requirements for the GPCTR1_SOURCEsignal.Figure 4-29. GPCTR1_SOURCE Signal TimingThe maximum allowed frequency is 20 MHz, with a minimum pulsewidth of 10 ns high or low. There is no minimum frequency limitation.The 20 MHz or 100 kHz timebase normally generates theGPCTR1_SOURCE unless you select some external source.GPCTR1_GATE SignalAny PFI pin can externally input the GPCTR1_GATE signal, which isavailable as an output on the PFI4/GPCTR1_GATE pin.As an input, the GPCTR1_GATE signal is configured in edge-detectionmode. You can select any PFI pin as the source for GPCTR1_GATE andconfigure the polarity selection for either rising or falling edge. You canuse the gate signal in a variety of different applications to perform sucht pt w t wt pt w= 50 ns minimum= 10 ns minimum
