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Chapter 2

Digital I/O

Note

Pause triggers are only sensitive to the level of the source, not the edge.

Digital Output Data Generation Methods

When performing a digital waveform operation, either software-timed or hardware-timed
generations can be performed.

Software-Timed Generations

With a software-timed generation, software controls the rate at which data is generated. Software
sends a separate command to the hardware to initiate each update. In NI-DAQmx,
software-timed generations are referred to as on-demand timing. Software-timed generations are
also referred to as immediate or static operations. They are typically used for writing a single
value out, such as a constant digital value.

Hardware-Timed Generations

With a hardware-timed generation, a digital hardware signal controls the rate of the generation.
This signal can be generated internally on your device or provided externally.

Hardware-timed generations have several advantages over software-timed generations:
•

The time between samples can be much shorter.

•

The timing between samples can be deterministic.

•

Hardware-timed acquisitions can use hardware triggering.

Hardware-timed operations can be buffered or hardware-timed single point (HWTSP). A buffer
is a temporary storage in computer memory for to-be-transferred samples.
•

Hardware-timed single point (HWTSP)

—Typically, HWTSP operations are used to

write single samples at known time intervals. While buffered operations are optimized for
high throughput, HWTSP operations are optimized for low latency and low jitter. In
addition, HWTSP can notify software if it falls behind hardware. These features make
HWTSP ideal for real time control applications. HWTSP operations, in conjunction with
the wait for next sample clock function, provide tight synchronization between the software
layer and the hardware layer. Refer to the NI Developer Zone document,

NI-DAQmx

Hardware-Timed Single Point Lateness Checking

, for more information. To access this

document, go to

ni.com/info

and enter the Info Code

daqhwtsp

.

•

Buffered

—In a buffered generation, data is moved from a PC buffer to the device’s

onboard FIFO using DMA before it is written to the output lines one sample at a time.
Buffered generation typically allow for much faster transfer rates than non-buffered
acquisitions because data is moved in large blocks, rather than one point at a time.
One property of buffered I/O operations is the sample mode. The sample mode can be either
finite or continuous:
–

Finite sample mode generation refers to the generation of a specific, predetermined
number of data samples. Once the specified number of samples has been written out,
the generation stops.

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Содержание NI 6614

Страница 1: ...NI 6614 User Manual NI 6614 User Manual August 2013 374038A 01...

Страница 2: ...ses and current events National Instruments Corporate Headquarters 11500 North Mopac Expressway Austin Texas 78759 3504 USA Tel 512 683 0100 For further support information refer to the Technical Supp...

Страница 3: ...Instruments shall not be liable for any delay in performance due to causes beyond its reasonable control The warranty provided herein does not cover damages defects malfunctions or service failures c...

Страница 4: ...INJURY TO A HUMAN 2 IN ANY APPLICATION INCLUDING THE ABOVE RELIABILITY OF OPERATION OF THE SOFTWARE PRODUCTS CAN BE IMPAIRED BY ADVERSE FACTORS INCLUDING BUT NOT LIMITED TO FLUCTUATIONS IN ELECTRICAL...

Страница 5: ...ercial areas To minimize interference with radio and television reception and prevent unacceptable performance degradation install and use this product in strict accordance with the instructions in th...

Страница 6: ...Trigger Signal 2 7 DI Reference Trigger Signal 2 8 DI Pause Trigger Signal 2 9 Digital Output Data Generation Methods 2 10 Software Timed Generations 2 10 Hardware Timed Generations 2 10 Digital Outpu...

Страница 7: ...1 Frequency Measurement 3 11 Frequency Measurement Considerations 3 11 Frequency Measurement Methods 3 13 Period Measurement 3 19 Pulse Width Measurement 3 19 Channel Settings 3 20 Timing Settings 3 2...

Страница 8: ...ggering Settings 4 6 Buffer Considerations 4 7 Generating Complex Digital Waveform or Timing Pattern 4 7 Create Channel 4 8 Channel Settings 4 8 Timing Settings 4 8 Triggering Setting 4 8 Buffer Consi...

Страница 9: ...Precision Clock 7 3 Using the OCXO to Overdrive the PXI Backplane Clock 7 4 Chapter 8 PXI Triggers PXI_Trigger 0 7 8 1 PXI_STAR 8 1 PXIe_DSTAR A C 8 1 Chapter 9 Bus Interface Data Transfer Methods 9...

Страница 10: ...ration Procedure Contains instructions for calibrating the NI 6614 NI 6614 Specifications Contains specifications specific to the NI 6614 NI DAQmx Help Contains API overviews general information about...

Страница 11: ...you plan to use with the device 1 Installing application software Refer to the installation instructions that accompany your software 2 Installing NI DAQmx The DAQ Getting Started documents contain st...

Страница 12: ...d 68 conductor cable R6868 cable Unshielded 68 conductor flat ribbon cable BNC 2121 BNC connector block with built in test features CA 1000 Configurable connector accessory SCB 68A Shielded screw conn...

Страница 13: ...d for timing input or output it is called PFI x where x is a number between 0 and 39 representing the PFI line number The same physical pin has two different names depending on whether it is used for...

Страница 14: ...cept for the default counter source input pins CI is not populated on the default source input pins in order to allow the measurement of higher speed input signals Table 2 2 lists the lines that do no...

Страница 15: ...le sample of data Each of the DIO lines can be used as a static DI or DO line You can use static DIO lines to monitor or control digital signals Each DIO can be individually configured as a digital in...

Страница 16: ...d across the bus fast enough the FIFO becomes full New acquisitions will overwrite data in the FIFO before it can be transferred to host memory The device generates an error in this case With continuo...

Страница 17: ...ignal DI Sample Clock Timebase Signal DI Start Trigger Signal DI Reference Trigger Signal DI Pause Trigger Signal Signals with an support digital filtering Refer to the PFI Filters section of Chapter...

Страница 18: ...rdware can stop it once a finite acquisition completes When using the DI timing engine you also can specify a configurable delay from DI Start Trigger to the first DI Sample Clock pulse By default thi...

Страница 19: ...as a posttriggered acquisition Retriggerable DI The DI Start Trigger can also be configured to be retriggerable The timing engine generates samples and converts clocks for the configured acquisition i...

Страница 20: ...number of posttrigger samples samples that occur after the reference trigger desired is the buffer size minus the number of pretrigger samples Once the acquisition begins the device writes samples to...

Страница 21: ...acquisition The internal sample clock pauses while the external trigger signal is active and resumes when the signal is inactive The active level of the pause trigger can be programmed to be high or...

Страница 22: ...s a temporary storage in computer memory for to be transferred samples Hardware timed single point HWTSP Typically HWTSP operations are used to write single samples at known time intervals While buffe...

Страница 23: ...ded new data cannot be written to the FIFO To use FIFO regeneration the entire buffer must fit within the FIFO size The advantage of using FIFO regeneration is that it does not require communication w...

Страница 24: ...routes the divided down DO Sample Clock Timebase to DO Sample Clock You can route many other signals to DO Sample Clock To view the complete list of possible routes see the Device Routes tab in MAX R...

Страница 25: ...s an output on the I O connector You might use DO Sample Clock Timebase if you want to use an external sample clock signal but need to divide the signal down If you want to use an external sample cloc...

Страница 26: ...lling edge of DO Start Trigger Routing DO Start Trigger Signal to an Output Terminal DO Start Trigger can be routed out to any PFI 0 39 PXI_Trig 0 7 or PXIe DSTARC terminal The output is an active hig...

Страница 27: ...r PXIe DSTARC terminal I O Protection Each DIO and PFI signal has limited protection against overvoltage undervoltage and overcurrent conditions as well as ESD events Avoid these fault conditions by f...

Страница 28: ...detectors The circuitry ORs the output of all enabled change detectors from every DI signal The result of this OR is the Change Detection Event signal Change detection performs bus correlation by con...

Страница 29: ...0 kHz clocks to generate the filter clock The following is an example of low to high transitions of the input signal High to low transitions work similarly Assume that an input terminal has been low f...

Страница 30: ...lding a valid transition indefinitely If all the bus line transitions become stable in less than one filter clock period and the bus period is more than two filter clock periods then all the bus lines...

Страница 31: ...ure 2 17 shows P1 0 3 configured for digital input and P1 4 7 configured for digital output Digital input applications include receiving TTL signals and sensing external device states such as the stat...

Страница 32: ...e NI 6614 can be used in the following digital I O applications Static digital input Static digital output Digital waveform generation Digital waveform acquisition DI change detection Note For more in...

Страница 33: ...ANSI C examples refer to the KnowledgeBase document Where Can I Find NI DAQmx Examples by going to ni com info and entering the Info Code daqmxexp For additional examples refer to zone ni com Signal...

Страница 34: ...lso contains an embedded counter Embedded Ctrn for use in what are traditionally two counter measurements and generations The embedded counters cannot be programmed independent of the main counter and...

Страница 35: ...about which signals can be used as the source Counter Input Applications The following sections list the various counter input applications available Edge Counting Pulse Measurement Semi Period Measu...

Страница 36: ...unt direction When the signal is high the counter counts up when the signal is low the counter counts down You can set which signal to monitor via CI CountEdges DirTerm Timing Settings The timing sett...

Страница 37: ...can change these behaviors by configuring DAQmx Trigger properties Using an Arm Start Trigger Use an Arm Start Trigger to have the counter begin counting in response to a hardware trigger 1 Set ArmSta...

Страница 38: ...a hardware signal set the following DAQmx Channel properties 1 Set CI CountEdges CountReset Enable to True 2 Set CI CountEdges CountReset Term to select the signal that causes the count to reset 3 Set...

Страница 39: ...utEvent OutputBehavior CtrOutEvent Pulse Polarity and CtrOutEvent Toggle IdleState Cascading Counters You can cascade two counters to make a single 64 bit counter For example assuming that you want to...

Страница 40: ...hannel Settings By default the counter measures the pulse on a default PFI terminal Refer to Chapter 5 Counter Signal Routing for more information begins measuring on a rising edge That is the counter...

Страница 41: ...ls DAQmx Start Task 2 The device measures the first full pulse on the signal to measure 3 The device waits until you call DAQmx Read The device ignores the signal to measure while waiting 4 The device...

Страница 42: ...DAQmx Start Task You can change this behavior by setting DAQmx Trigger properties To have the counter begin counting in response to a hardware trigger use an Arm Start Trigger 1 Set ArmStart TrigType...

Страница 43: ...rmation Semi Period Measurement Semi Period measurements are very similar to pulse measurements Refer to the Pulse Measurement section for more information In hardware both measurements are the same h...

Страница 44: ...uration can be either a fixed time or a fixed number of periods of the input signal That is to calculate frequency the counter can either measure the number of periods p that occur during a specified...

Страница 45: ...e device returns one frequency measurement for each sample clock If you use implicit timing and specify a measurement time the device returns the measurement after that amount of time If you use impli...

Страница 46: ...f cycles T2 of the timebase Figure 3 15 Frequency Measurement Sample Clock with Averaging At each sample clock the device stores T1 and T2 in a buffer DAQmx reads these values and uses the known frequ...

Страница 47: ...as the counter timebase set this property to a different terminal Sample Clock without Averaging With this method for each sample clock the counter detects the last full period of the signal to measur...

Страница 48: ...his method the device detects the first full period of the signal to measure The counter measures the duration of this period by counting the number of cycles T2 of the timebase DAQmx reads T2 and use...

Страница 49: ...Counters This measurement method requires two counters Counter N and Counter M For this measurement method Counter N creates a pulse equal to T1 periods of the signal to measure The device routes thi...

Страница 50: ...g for more information and use an onboard 100 MHz clock as the timebase To change the signals used for this measurement configure the following CI Freq Term The signal to measure comes from an input t...

Страница 51: ...g DAQmx Create channel CI Frequency Use this VI or function to create the channel CI Freq MeasMeth Set this property to High Frequency with 2 Counters Note that this measurement method requires two co...

Страница 52: ...measurements are similar to Frequency measurements For example use CI Period Term to change the signal to measure Pulse Width Measurement Note This section describes Pulse Width measurements For Puls...

Страница 53: ...s the units of the measurement Timing Settings The timing settings determine when the device measures the signal Figure 3 20 shows an example of On Demand timing On Demand No sample clock By default t...

Страница 54: ...iming use the DAQmx Timing Sample Clock VI or function Trigger Settings By default the counter begins measuring when software calls DAQmx Start Task You can change this behavior by setting DAQmx Trigg...

Страница 55: ...an input to the counter by enabling a filter Refer to the PFI Filters section in Chapter 6 PFI for more information If you route the same PFI signal to multiple destinations you should enable the Sync...

Страница 56: ...irst Edge Specifies on which edge of the first signal rising or falling the device begins the measurement CI TwoEdgeSep Second Edge Specifies on which edge of the second signal rising or falling the d...

Страница 57: ...the device stores one measurement The one measurement is the time between the most recent pair of beginning and ending events to occur before the sample clock Figure 3 26 shows an example of Sample Cl...

Страница 58: ...ature and Two Pulse Encoder Overview The NI 6614 can make angular and linear position measurements using quadrature and two pulse encoders Quadrature Encoders A quadrature encoder can have up to three...

Страница 59: ...pect to channels A and B You must then ensure that channel Z is high during at least a portion of the phase you specify for reload In Figure 3 30 the reload phase is when both channel A and channel B...

Страница 60: ...e encoders set this to XI X2 or X4 decoding Z index enables z index phase z index value If the encoder has a z output set z index enable to True Set the z index phase to indicate when to reset the cou...

Страница 61: ...Demand Timing Sample Clock To precisely control when the device reads the encoder use the DAQmx Timing Sample Clock vi or function With this vi or function you can set the source and rate of the Samp...

Страница 62: ...PFI Filters section in Chapter 6 PFI for more information If you route the same PFI signal to multiple destinations you should enable the Synchronization feature Refer to Chapter 6 PFI for more infor...

Страница 63: ...duty cycle Generating a periodic waveform with variable frequency and duty cycle Generating a complex digital waveform or timing pattern Figure 4 1 Samples of Counter Output Applications Generating a...

Страница 64: ...timebase is 100 MHz so a tick is 10 ns To specify the pulses in terms of ticks use the DAQmx Create Channel CO Pulse Generation Ticks VI or function Frequency and Duty Cycle To specify the pulses in t...

Страница 65: ...s generating pulses Note Even if the Start Delay is set to 0 the NI 6614 inserts a minimum delay equal to two ticks of the counter timebase Start DigEdge DigFltr Enable Start DigEdge DigFltr MinPulseW...

Страница 66: ...Ticks A tick is one period of the Counter Timebase By default the timebase is 100 MHz so a tick is 10 ns To specify the waveform in terms of ticks use the DAQmx Create Channel CO Pulse Generation Tick...

Страница 67: ...n Generating a Waveform with Variable Frequency and Duty Cycle Figure 4 7 shows an example of a waveform with variable frequency and duty cycle Figure 4 7 Waveform with Variable Frequency and Duty Cyc...

Страница 68: ...e inputs determine the initial waveform DAQmx Create Channel CO Pulse Generation Ticks The high ticks and low ticks inputs determine the initial waveform Channel Settings By default the counter output...

Страница 69: ...fferent ways to support a wide variety of applications For example you can configure DAQmx to read data from the buffer once and stop read data from the buffer multiple times or continuously update th...

Страница 70: ...Timing Implicit VI or function Triggering Setting By default the NI 6614 begins generating the pulses when you call the DAQmx Start Task VI or function The NI 6614 can also begin generating pulses in...

Страница 71: ...frequency division use the steps described in Generating a Waveform with Constant Frequency and Duty Cycle Also Route the input signal f to be the counter timebase using the Co CtrTimebaseSrc DAQmx C...

Страница 72: ...using the DAQmx Create Channel CO Pulse Generation Frequency VI or function Choose device name freqout for the counter input to this VI or function Set the frequency input to the desired value DAQmx w...

Страница 73: ...on the front panel I O connector any of the eight counters the Digital I O circuits other devices in your PXI chassis using backplane PXI signals such as PXI_TRIG 7 0 clocking circuitry Default Routin...

Страница 74: ...0 Pulse Width Semi Period Period Frequency Sample Clock or Low Frequency with One Counter Period Frequency High Frequency with Two Counters or Large Range with Two Counters PFI 39 PFI 35 PFI 31 PFI 27...

Страница 75: ...on tree on the left to view your device 3 Left click your device to select it 4 Click the Device Routes tab at the bottom of the middle pane to see routes that can be made within your device Matching...

Страница 76: ...s in Routing Options The column labeled device name Ctr2Gate lists all signals that can be routed to Ctr2Gate and those are therefore all the signals that can be used as the Pause Trigger Table 5 3 Ma...

Страница 77: ...line Each PFI line is similar Figure 6 1 PFI Circuitry When a terminal is used as a timing input or output signal it is called PFI x where x is an integer from 0 to 39 When a terminal is used as a st...

Страница 78: ...inputs and whether the input is edge or level sensitive Exporting Timing Output Signals Using PFI Terminals You can route any of the following timing signals to any PFI terminal configured as an outpu...

Страница 79: ...functionality inside the device Refer to the DI Change Detection section of Chapter 2 Digital I O for more information Connecting PFI Input Signals All PFI input connections are referenced to D GND F...

Страница 80: ...low to high transition on an input that has a custom filter set to N 5 Figure 6 3 Filter Example Enabling filters introduces jitter on the input signal The maximum jitter is one period of the timebase...

Страница 81: ...n input do not drive the line with voltages outside of its normal operating range Treat the DAQ device as you would treat any static sensitive device Always properly ground yourself and the equipment...

Страница 82: ...GND pin Table 6 2 shows the corresponding GND pin for each PFI pin If you are using a 68 pin screw terminal accessory or designing your own accessory make sure to connect your GND signal to the appro...

Страница 83: ...22 62 PFI 23 P0 23 PFI 24 P0 24 30 PFI 25 P0 25 PFI 26 P0 26 65 PFI 27 P0 27 PFI 28 P0 28 33 PFI 29 P0 29 PFI 30 P0 30 68 PFI 31 P0 31 PFI 32 P1 0 42 PFI 33 P1 1 39 PFI 34 P1 2 42 PFI 35 P1 3 41 PFI 3...

Страница 84: ...rom one of the following sources Onboard oscillator Various signals as shown in Figure 7 1 20 MHz Timebase The 20 MHz Timebase also can be used as the Source input to the 32 bit general purpose counte...

Страница 85: ...tes the internal timebases Caution Do not disconnect an external reference clock once the devices have been synchronized or are used by a task Doing so may cause the device to go into an unknown state...

Страница 86: ...independently to each peripheral slot in a PXI chassis Synchronizing Multiple Devices Refer to the following sections for information about synchronizing multiple NI 6614 devices PXI Express Devices...

Страница 87: ...to generate PXI_Clk10 and PXIe_Clk100 backplane reference clocks The chassis independently buffers and distributes the backplane clocks to each peripheral slot with less than 1ns of skew This allows f...

Страница 88: ...NI 6614 in the System Timing Slot Front Panel I O Acquisition Generation Subsystem 100 MHz PLL Other External Ref Clk DAQmx Timing Property RefClk Src Onboard 10 MHz OCXO PXIe_Clk100 On Board 10 MHz...

Страница 89: ...I_Trigger 0 7 A PXI chassis provides eight bused trigger lines PXI_Trigger 0 7 to each module in a system In a PXI chassis with more than eight slots PXI trigger lines may be divided into multiple ind...

Страница 90: ...PXIe DSTAR Line Descriptions Trigger Line Purpose PXIe_DSTARA Distributes high speed high quality clock signals from the system timing slot to the peripherals input PXIe_DSTARB Distributes high speed...

Страница 91: ...are and software technology to achieve high throughput rates and increase system utilization DMA is the default method of data transfer for PXI Express devices NI 6614 devices have ten fully independe...

Страница 92: ...is responsible for transferring data Each read or write call in the program initiates the transfer of data Programmed I O is typically used in software timed on demand operations PXI Express Consider...

Страница 93: ...ncludes verifying and adjusting the frequency accuracy of the onboard OCXO National Instruments recommends that you calibrate the NI PXIe 6614 yearly In order to calibrate and adjust your device to co...

Страница 94: ...ional Instruments A 1 A Pinout and Signal Descriptions Figure A 1 shows the NI PXIe 6614 pinout The descriptions beside each pin are in the following format Signal Name DIO Context Counter Context Def...

Страница 95: ...19 P0 19 CTR 5 SOURCE CTR 4 OUT PFI 20 P0 20 D GND PFI 23 P0 23 CTR 4 SOURCE PFI 24 P0 24 CTR 3 OUT D GND PFI 27 P0 27 CTR 3 SOURCE PFI 28 P0 28 CTR 2 OUT D GND PFI 31 P0 31 CTR 2 SOURCE R GND RESERVE...

Страница 96: ...ervice Program SSP with the purchase of most software products and bundles including NI Developer Suite NI also offers flexible extended contract options that guarantee your SSP benefits are available...

Страница 97: ...rt and Professional Services You also can visit the Worldwide Offices section of ni com niglobal to access the branch office Web sites which provide up to date contact information support phone number...

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