National Instruments BNC-2121 User manual

USER GUIDE
BNC-2121 Connector Accessory
for 660XDevices
The BNC-2121 connector accessory is a terminal block that connects
signals to a 660Xcounter device and can be used to test features of
a660Xdevice. Use this guide to install and connect signals to a BNC-2121
connector accessory for testing or for performing counter applications.
For specific information about using a 660Xdevice, refer to the 660X User
Manual.
What You Need to Get Started
You need the following items to install and use the BNC-2121 connector
accessory.
❑BNC-2121 connector accessory
❑BNC-2121 Connector Accessory for 660X Devices User Guide
❑660Xdevice
❑660X User Manual
❑68-position cable, such as the SH68-68-D1 or R6868
❑BNC cables
❑Wire no larger than 24 AWG
❑Wire strippers

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Connecting the BNC-2121 to a 660XDevice
You can use a BNC-2121 with any installed 660Xdevice. Connect one end
of a 68-position cable to a 660Xdevice and the other end to the
I/O connector on the BNC-2121, as shown in Figure 1.
Figure 1. Connecting a BNC-2121 to a 660XDevice
Note If the power LED indicator does not light up, check the cable connections to make
sure the cable is connected securely.
Connecting Signals to the BNC-2121
Connect signals using the spring terminals or BNC connectors shown in
Figure 2. For pinout diagrams and more specific information about
connecting signals, refer to the 660X User Manual.

©National Instruments Corporation 3 BNC-2121 Connector Accessory for 660X Devices
Figure 2. BNC-2121 Front Panel
1 Warning Label
2 PFI Line Spring Terminal
3 Quadrature Encoder Output
Spring Terminals
4 Digital Trigger Output Spring
Terminal
5 Frequency Output Spring
Terminal ()
6 +5 V Output Spring Terminal
7 GND Terminal
8 Quadrature Encoder Knob
9 Digital Trigger Button
10 Digital Trigger Filtering Switch
11 68-Position I/O Connector
12 Power LED Indicator
13 Digital Line LED State Indicator
14 BNC Connectors for
Counters 0 and 1
15 User-Defined BNC Connector
16 Spring Terminals for
User-Defined BNC Connectors
17 Frequency Selection Switch
18 Frequency Adjust Knob
19 Digital Trigger Line
LED State Indicator
!
PFI
21
23
25
27
29
31
33
35
37
39
DIGITAL I/O INDICATORS
P0.0
P0.2
P0.4
P0.6
P0.1
P0.3
P0.5
P0.7
P0.1
P0.3
GND
P0.5
P0.7
GND
SRC7
GND
UP/DN6
SRC6
GND
UP/DN5
SRC5
GND
UP/DN7
P0.0
P0.2
GND
P0.4
P0.6
GND
OUT7
GATE7
GND
OUT6
GATE6
GND
OUT5
GATE5
GND
PFI
0
2
4
6
8
10
12
14
16
18
OUT4
GATE4
GND
OUT3
GATE3
GND
OUT2
GATE2
GND
OUT1
GATE1
GND
OUT0
GATE0
RESERVE1
UP/DN4
SRC4
GND
UP/DN3
SRC3
GND
UP/DN2
SRC2
GND
UP/DN1
SRC1
GND
UP/DN0
SRC0
RESERVE2
PFI
20
22
24
26
28
30
32
34
36
38
PFI LINES 0-39
PWR
PFI LINES 32-39
USER DEFINED FUNCTIONS
OUT1
PFI 32
UP/DN1
PFI 33
SRC1
PFI 35
GATE1
PFI 34
OUT0
PFI 36
UP/DN0
PFI 37
SRC0
PFI 39
GATE0
PFI 38
10 Hz-200 Hz
150 Hz-20 kHz
14 kHz-1 MHz
Frequency
Selection
Frequency
Adjust
LO HI
( ) ( )
USER 1 USER 2
USER 4USER 3
USER 5 USER 6
Filtering
OFF ON
Digital Trigger (TRIGGER)
Quadrature Encoder
24 Pulses/rev (A,B)
ENCODER A
ENCODER B
TRIGGER
+5V
GND
USER 1
USER 2
USER 3
USER 4
USER 5
USER 6
Drive only one signal per PFI line
using either a BNC, a spring
terminal or the 660X device.
!
Electrostatic
Sensitive
Connectors
BNC-2121
PFI
1
3
5
7
9
11
13
15
17
19
16
14
15
2
13
3
4
5
6
7
12
9
19
18
1
11
8
17
10

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Overview of Connecting to the BNC-2121
The BNC-2121 has two main areas of connectivity: the PFI lines and the
user-defined functions.
The PFI lines include bidirectional spring terminals, PFI <0..39>, and
bidirectional BNC connectors, PFI <32..39>. Both connection types
provide access to the respective PFI lines on the 660Xdevice. The
digital I/O indicators reflect the state of the dedicated digital I/O P.<0..7>
spring terminals.
The user-defined function connections include the following:
• Six output spring terminals—Encoder A, Encoder B, Trigger,
Square Wave ( ), +5 V, and GND
• Controls for the outputs listed above—Quadrature Encoder, Digital
Trigger, Frequency Selection, and Frequency Adjust
Table 1 lists the controls and the outputs associated with them.
• Six bidirectional, user-defined spring terminals—USER <1..6>
• Six user-defined BNC connectors—USER <1..6>
Note The user-defined spring terminals are internally mapped one-to-one to
corresponding BNC connectors. For example, the USER 1 spring terminal is internally
wired to the USER 1 BNC connector. When you want BNC connections for counters other
than 0 or 1, use the user-defined connections.
Table 1. User-Defined Function Controls and the Corresponding Outputs
Controls Spring Terminal Outputs
Quadrature Encoder Knob Encoder A
Quadrature Encoder Knob Encoder B
Digital Trigger Button Trigger
Frequency Selection
Frequency Adjust

©National Instruments Corporation 5 BNC-2121 Connector Accessory for 660X Devices
Connecting to the Spring Terminals
Use the BNC-2121 connector accessory to access the PFI lines on a
660Xdevice.
To make the connection, complete the following steps.
1. Using wire strippers, strip the wire insulation no more than 7 mm.
2. Connect a wire to a spring terminal on the BNC-2121 by depressing
the orange tab and inserting the stripped end of the wire fully into the
terminal.
Tip For the best performance, use twisted-pair wire. Connect one wire of the wire pair
from the signal on the peripheral device and the other end of the same twisted wire to the
signal on the BNC-2121. Connect the other wire of the wire pair to the ground of the
peripheral device and the other end to the ground (GND) spring terminal closest to the
signal.
Caution Make sure that no bare wire extends past the spring terminal. Exposed wire
increases the risk of a short circuit or a failure.
3. If you need to ground a signal, a ground (GND) spring terminal is
available between every two PFI lines. For details about grounding a
signal, refer to the 660X User Manual.
The user-defined functions area of the BNC-2121 has six user-defined
spring terminals, USER <1..6>, and six corresponding BNC connectors,
USER <1..6>. Use these spring terminals for either input or output. For
example, if you want to connect a BNC cable to GATE of a counter other
than Counter 0 or 1, connect a wire from the GATE spring terminal on the
660Xdevice to a user-defined spring terminal (USER 1) on the BNC-2121,
and the signal is available through the corresponding BNC connector
(USER 1).
The six other spring terminals (ENCODER A, ENCODER B, TRIGGER,
, +5 V, and GND) are used as signal outputs only. Follow steps 1 and 2
in this section to connect the output wires to the appropriate spring
terminals. Use the corresponding controls for each spring terminal, given
in Table 1, to regulate a signal.
Connecting to the BNC Connectors
Use the eight BNC connectors to access PFI <32..39> on a 660Xdevice.
Each line corresponds to SOURCE, GATE, OUT, and UP/DOWN of
counter 0 or 1.

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To make the connection, complete the following steps.
1. Insert one end of the BNC cable in one of the PFI <32..39>
BNC connectors.
2. Connect the other end of the BNC cable to the output device.
In addition to the BNC connectors associated with the PFI lines of the
660Xdevice, the BNC-2121 has six user-defined BNC connectors,
USER <1..6>, that are associated with six corresponding user-defined
spring terminals USER <1..6>. You can use these BNC connectors for
either input or output.
Testing User-Defined Functions
You can use the BNC-2121 to test the following features on the
660Xdevice.
Producing a +5 V Pulse
Use the digital trigger to test an application that counts or measures pulses.
Press the Digital Trigger button to produce a +5 V pulse for as long as the
button is pressed, causing the LED to light up. When you release the button,
the trigger line goes low. You can access the digital trigger by connecting
a wire to the Trigger spring terminal. The digital trigger also can simulate
a channel Z pulse for quadrature encoder functions.
The lowpass filter on the BNC-2121 is designed to remove glitches on the
trigger output. If you want to use unconditional trigger output to test the
debouncing filter on a 660Xdevice, flip the Filtering switch to the OFF
position, connect the trigger output to a PFI line, and programmatically
enable the debouncing filter on the 660Xdevice. For all other applications,
flip the Filtering switch to the ON position.
Measuring Position
The BNC-2121 can produce 24 pulses per encoder revolution. You can test
this feature using the following programs.
• C interface—TIOquadEncoderPosMeasure.c located in
Program Files/National Instruments/Measurement
Studio/CVI/Samples/DAQ/Ctr
• LabVIEW—Measure Position VI located in Program Files/
National Instruments/LabVIEW/Examples/DAQ/Counter/
NI-TIO.llb

©National Instruments Corporation 7 BNC-2121 Connector Accessory for 660X Devices
To measure position using counter 0 of a 660Xdevice, make the following
connections.
1. Connect a wire from channel A to SOURCE of counter 0
(default PFI 39).
2. Connect a wire from channel B to UP/DOWN of counter 0
(default PFI 37).
Note If you want to simulate a Z channel, connect a wire from the Trigger spring terminal
to GATE of counter 0 (default PFI 38).
Creating a Square Wave
The BNC-2121 has a function generator that produces TTL-compatible
square waveforms.
To create a square wave, complete the following steps.
1. Access the square wave output by connecting signals to the spring
terminal.
2. Use the Frequency Selection switch to select a frequency range of
10 Hz–200 Hz, 150 Hz–20 kHz, or 14 kHz–1 MHz.
3. Adjust the frequency within the range you selected by turning the
Frequency Adjust knob.
Viewing the State of the DIO Lines
The eight Digital I/O indicators indicate the state of PFI <0..7> on a
660Xdevice. When the LED is lit, the channel is in the high state. When
the LED is off, the channel is in the low state.
Using the BNC-2121 to Perform Counter Applications
This section explains how to connect signals to the BNC-2121 to test,
demonstrate, and perform counter applications with a 660Xdevice. To find
the correct application to perform, refer to the 660X User Manual.
Counter program examples mentioned in this section are in the following
locations.
•NI-DAQ—
Measurement Studio\CVI\Samples\DAQ\Ctr
•LabVIEW—Program Files\National Instruments\
LabVIEW\Examples\DAQ\Counter\NI.TIO.llb

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Simple Event Counting
To perform simple event counting, connect a wire from the spring
terminal to SOURCE of the selected counter. The 660Xdevice counts the
number of pulses that occur on SOURCE.
Alternatively, you can connect a wire from the Trigger spring terminal to
provide pulses on SOURCE.
Gated Event Counting
To perform gated event counting, complete the following steps.
1. Connect a wire from the spring terminal to SOURCE of the
selected counter.
2. Connect a wire from the Trigger spring terminal to GATE of the
selected counter.
3. Press and hold the Digital Trigger button to drive GATE into a high
state. The counter counts the pulses on SOURCE as long as GATE is
high.
4. Release the Digital Trigger button to drive GATE into a low state. The
counting halts and retains its value until you press the Digital Trigger
button again and counting continues.
Single Period Measurement
To take a single period measurement, complete the following steps.
1. In the C interface or in LabVIEW, select an internal timebase as
SOURCE of the selected counter.
2. Connect a wire from the spring terminal to GATE of the selected
counter. The counter counts the rising edges on SOURCE between two
active GATE edges. The period is this count multiplied by the period
of SOURCE.
Single Pulse-Width Measurement
To take a single pulse-width measurement, complete the following steps.
1. In the C interface or in LabVIEW, select an internal timebase as
SOURCE of the selected counter.
2. Connect a wire from the Trigger spring terminal to GATE of the
selected counter.
3. Press the Digital Trigger button to drive GATE into a high state.
The counter counts the rising edges on SOURCE while GATE is
active.
4. Release the Digital Trigger button to drive GATE into a low state.
The counter value is latched for a software read.

©National Instruments Corporation 9 BNC-2121 Connector Accessory for 660X Devices
Two-Signal Edge-Separation Measurement
To take a two-signal edge-separation measurement, complete the following
steps.
1. Connect a wire from the spring terminal to UP/DOWN of the
selected counter.
2. In the C interface or in LabVIEW, select an internal timebase as
SOURCE of the selected counter. As soon as UP/DOWN goes active,
the counter counts the edges on SOURCE.
3. Connect a wire from the Trigger spring terminal to GATE of the
selected counter.
4. Press the Digital Trigger button to drive GATE into an active state.
As soon as GATE goes active, the counter value is latched for a
software read.
Note UP/DOWN and AUX_LINE share the same PFI line on all counters.
Single Pulse Generation
To generate a single pulse, complete the following steps.
1. In the C interface or in LabVIEW, select an internal timebase as
SOURCE of the selected counter.
2. Specify the pulse delay and pulse width in the C interface or
LabVIEW.
3. To see the signal, connect an oscilloscope or analog input device to
OUT of the selected counter.
Single-Triggered Pulse Generation
To generate a single-triggered pulse, complete the following steps.
1. In the C interface or in LabVIEW, select an internal timebase as
SOURCE of the selected counter.
2. Specify the pulse delay and pulse width in the C interface or
LabVIEW.
3. Connect a wire from the Trigger spring terminal to GATE of the
selected counter.
4. Press the Digital Trigger button to generate a single pulse. One pulse
is generated on OUT of the counter when the trigger is received.
5. To see the signal, connect an oscilloscope or analog input device to
OUT of the selected counter.

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Retriggerable Single Pulse Generation
To generate a retriggerable single pulse, complete the following steps.
1. In the C interface or in LabVIEW, select an internal timebase as
SOURCE of the selected counter.
2. Specify the pulse delay and pulse width in the C interface or
LabVIEW.
3. Connect a wire from the Trigger spring terminal to GATE of the
selected counter.
4. Press the Digital Trigger button to generate a pulse. Any time you
want an additional pulse, press the Digital Trigger button to generate
a pulse on OUT of the counter.
Note A pulse is generated on every active GATE edge.
5. To see the signal, connect an oscilloscope or analog input device to
OUT of the selected counter.
Continuous Pulse-Train Generation
To generate a continuous pulse-train, complete the following steps.
1. In the C interface or in LabVIEW, select an internal timebase as
SOURCE of the selected counter.
2. In the C interface or in LabVIEW, specify the frequency and duty cycle
of the pulse train.
3. To see the signal, connect an oscilloscope or analog input device to
OUT of the selected counter.
Frequency Shift-Keying
To perform frequency shift-keying, complete the following steps.
1. In the C interface or in LabVIEW, select an internal timebase as
SOURCE of the selected counter.
2. Connect a wire from the Trigger spring terminal to GATE of the
selected counter.
3. Press the Digital Trigger button to drive GATE into a high state.
4. Release the Digital Trigger button to drive GATE into a low state.
5. To see the signal, connect an oscilloscope or analog input device to
OUT of the selected counter.