The following table lists the default input terminals for various counter measurements. You can use a different PFI line for any of the input terminals. To change the PFI input for a measurement, use the NI-DAQmx channel properties/attributes.

Note You cannot change the default PFI lines for quadrature encoder-based position measurements on NI 660x devices.
Measurement Ctr0 Ctr1 Ctr2 Ctr3 Ctr4 Ctr5 Ctr6 Ctr7 gpsTimestampCtr0 (NI 6608 Only) gpsTimestampCtr1 (NI 6608 Only)
Count Edges
  • Edges: PFI 39
  • Count Direction: PFI 37
  • Edges: PFI 35
  • Count Direction: PFI 33
  • Edges: PFI 31
  • Count Direction: PFI 29
  • Edges: PFI 27
  • Count Direction: PFI 25
  • Edges: PFI 23
  • Count Direction: PFI 21
  • Edges: PFI 19
  • Count Direction: PFI 17
  • Edges: PFI 15
  • Count Direction: PFI 13
  • Edges: PFI 11
  • Count Direction: PFI 9
N/A N/A
Pulse Width Measurement PFI 38 PFI 34 PFI 30 PFI 26 PFI 22 PFI 18 PFI 14 PFI 10 N/A N/A
Period/Frequency Measurement (Low Frequency with One Counter) PFI 38 PFI 34 PFI 30 PFI 26 PFI 22 PFI 18 PFI 14 PFI 10 N/A N/A
Period/Frequency Measurement (High Frequency with Two Counters) PFI 39 PFI 35 PFI 31 PFI 27 PFI 23 PFI 19 PFI 15 PFI 11 N/A N/A
Period/Frequency Measurement (Large Range with Two Counters) PFI 39 PFI 35 PFI 31 PFI 27 PFI 23 PFI 19 PFI 15 PFI 11 N/A N/A
Semiperiod Measurement PFI 38 PFI 34 PFI 30 PFI 26 PFI 22 PFI 18 PFI 14 PFI 10 N/A N/A
Two-Edge Separation Measurement
  • Start: PFI 37
  • Stop: PFI 38
  • Start: PFI 33
  • Stop: PFI 34
  • Start: PFI 29
  • Stop: PFI 30
  • Start: PFI 25
  • Stop: PFI 26
  • Start: PFI 21
  • Stop: PFI 22
  • Start: PFI 17
  • Stop: PFI 18
  • Start: PFI 13
  • Stop: PFI 14
  • Start: PFI 9
  • Stop: PFI 10
N/A N/A
Position Measurement
  • A: PFI 39
  • B: PFI 37
  • Z: PFI 38
  • A: PFI 35
  • B: PFI 33
  • Z: PFI 34
  • A: PFI 31
  • B: PFI 29
  • Z: PFI 30
  • A: PFI 27
  • B: PFI 25
  • Z: PFI 26
  • A: PFI 23
  • B: PFI 21
  • Z: PFI 22
  • A: PFI 19
  • B: PFI 17
  • Z: PFI 18
  • A: PFI 15
  • B: PFI 13
  • Z: PFI 14
  • A: PFI 11
  • B: PFI 9
  • Z: PFI 10
N/A N/A
GPS Timestamp Measurement N/A N/A N/A N/A N/A N/A N/A N/A
  • PFI 7
  • Synch. Source: PFI 7
  • PFI 7
  • Synch. Source: PFI 7
Note The NI 6601 has only four counters (ctr0-ctr3). The entries in the previous table for cntr4, cntr5, cntr6, and cntr7 do not apply for that device.

The following table lists the output terminals for counter output. You can use a different PFI line for any of the output terminals.

Ctr0 Ctr1 Ctr2 Ctr3 Ctr4 Ctr5 Ctr6 Ctr7
PFI 36 PFI 32 PFI 28 PFI 24 PFI 20 PFI 16 PFI 12 PFI 8
Note The NI 6601 has only four counters (ctr0-ctr3). The entries in the previous table for cntr4, cntr5, cntr6, and cntr7 do not apply for that device.

NI 6624 Issues

The eight PFI lines listed as the defaults for counter output are dedicated for output, and they are the only terminals you can use for counter output. For example, you can use PFI 8 (the default for Ctr7) as the output terminal for any counter, but you cannot use it as an input terminal.

When using counter output, if the Idle State attribute/property is low, the optocouplers on the NI 6624 will still be driving your output load. Set the Idle State attribute/property to high to prevent driving the output after your task completes.