Table Of Contents

USB-6251 BNC Pinout

Version:
    Last Modified: March 21, 2017

    Table 1. Default Counter/Timer Terminals
    Counter/Timer Signal Default PFI Terminal
    CTR 0 SRC PFI 8
    CTR 0 GATE PFI 9
    CTR 0 AUX PFI 10
    CTR 0 OUT PFI 12
    CTR 0 A PFI 8
    CTR 0 Z PFI 9
    CTR 0 B PFI 10
    CTR 1 SRC PFI 3
    CTR 1 GATE PFI 4
    CTR 1 AUX PFI 11
    CTR 1 OUT PFI 13
    CTR 1 A PFI 3
    CTR 1 Z PFI 4
    CTR 1 B PFI 11
    FREQ OUT PFI 14
    Table 2. Signal Descriptions
    Signal Reference Description

    AI GND

    Analog Input GroundThese terminals are the reference point for single-ended AI measurements in RSE mode and the bias current return point for DIFF measurements. All ground references—AI GND and D GND—are connected on the device.

    AI <0..7>

    Varies

    Analog Input Channels—For differential measurements, the BNC pin and shield are the positive and negative inputs of the differential analog input channel. Refer to the M Series User Manual for information about the FS/GS switch selection and single-ended measurement options.

    AI SENSE

    Analog Input SenseIn NRSE mode, the reference for each AI <0..15> signal is AI SENSE.

    AO <0,1>

    Analog Output Channels—These terminals supply voltage output.

    D GND

    Digital GroundD GND supplies the reference for port 0, port 1, port 2 digital channels, PFI, and +5 V. All ground references—AI GND and D GND—are connected on the device.

    P0.<0..7>

    D GND Port 0 Digital I/O Channels—You can configure each signal individually as an input or output.

    APFI 0

    AI GND

    Analog Programmable Function Interface ChannelsEach APFI signal can be used as AO external reference inputs for AO, or as an analog trigger input. APFI are referenced to AI GND when they are used as analog trigger inputs. APFI are referenced to an analog ground when they are used as AO external offset or reference inputs.

    +5 V D GND

    +5 V Power Source—These terminals provide a fused +5 V power source.

    PFI <0..7>/P1.<0..7>, PFI <8..15>/P2.<0..7>

    D GND

    Programmable Function Interface or Digital I/O Channels—Each of these terminals can be individually configured as a PFI terminal or a digital I/O terminal.

    As an input, each PFI terminal can be used to supply an external source for AI, AO, DI, and DO timing signals or counter/timer inputs. As a PFI output, you can route many different internal AI, AO, DI, or DO timing signals to each PFI terminal. You can also route the counter/timer outputs to each PFI terminal. As a port 1 or port 2 digital I/O signal, you can individually configure each signal as an input or output.

    USER <1,2>

    User-Defined Channels—The USER BNC connectors allow you to use a BNC connector for a digital or timing I/O signal of your choice. The USER BNC connectors are internally routed to the USER screw terminals.

    CHS GND

    Chassis Ground—This terminal connects to the device metal enclosure. You can connect your cable’s shield wire to CHS GND for a ground connection.

    Table 3. LED State/Device Status
    POWER (+5 V) ACTIVE READY Device Status
    Off Off Off Device is not powered.
    On Off Off Device is powered but not connected to the host computer, or the host computer does not have the correct driver version. Detection can take 30 to 45 seconds.
    On Off On Device is configured, but there is no activity over the bus.
    On On On Device is configured and there is activity over the bus.
    On Blinking On

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