Copyright: ©Tektronix, Inc.
Citation: Excerpt of TDSDDM2 Online Help.


Welcome to the TDSDDM2 Disk Drive Measurements Program

The TDSDDM2 Disk Drive Measurements Application is a Java–based application that enhances basic capabilities of some Tektronix oscilloscopes.

The application:

•	Provides disk drive measurements

•	Displays the results as statistics or as a plot

•	Saves the results to a data log file

What do you want to do?

  Study Online Help and Related Documentation

  Read Product Description

  Go to Installation Procedures

To return to the Table of Contents, select Help Topics from the Help Top Menu.


 Online Help and Related Documentation

Access information on how to operate the oscilloscope and application through the following related documents and online help.

What do you want to do?

Using Online Help

Conventions

Related Documentation

Provide feedback on this Tektronix product.


Related Documentation

In addition to the Online Help, you can access other information on how to operate the oscilloscope and application through the following related documents:

•	Installation Instructions; the installation instructions provide information on how to install software.

•	Oscilloscope Information; the user manual for your oscilloscope provides general information on how to operate the oscilloscope.

•	Programmer Information; the online help for your oscilloscope provides details on how to use GPIB commands to control the oscilloscope.

You can also download the file with programmer information and examples from the Tektronix web site.  Refer to the installation manual for information on how to download the file.

Refer to the Optional Applications Software on a Windows-Based Oscilloscope Installation Manual for the following information:

•	Software warranty

•	List of all available applications, compatible oscilloscopes, and relevant software and firmware version numbers

•	Applying a new label

•	Installing an application

•	Enabling an application

•	Downloading updates from the Tektronix Website

You can find a PDF (portable document format) file for this document in the Documents directory on the Optional Applications Software on a Windows-Based Oscilloscope CD. The CD booklet only contains information on installing the application from the CD and on how to apply a new label.

See Also

Using Online Help


Conventions

Online help uses the following conventions:

•	Refers to the TDSDDM2 Disk Drive Measurements Application as the TDSDDM2 application or as the application.

•	Refers to any product on which this application runs as an "oscilloscope."

•	Menus and options may appear in gray if they are beyond the capability of the oscilloscope.

•	Displays of an oscilloscope are from a TDS7104 model; there may be subtle differences in the displays from other types of oscilloscopes.

•	When steps require a sequence of selections using the application interface, the ">" delimiter marks each transition between a menu and an option.  For example, one of the steps to recall a setup file would appear as Measurements> Save/Recall> Recall.


Feedback

Tektronix values your feedback on our products. To help us serve you better, please send us any suggestions, ideas, or other comments you may have regarding your oscilloscope.

Direct your feedback to us via email to techsupport@tektronix.com or FAX at (503) 627-5695, and include the following information.  Please be as specific as possible.

General information:

•	Oscilloscope model number and hardware options, if any

•	Probes used

•	Your name, company, mailing address, phone number, FAX number

•	Please indicate if you would like to be contacted by Tektronix regarding your suggestion or comments.

Application specific information:

•	Software version number

•	Description of the problem such that technical support can duplicate the problem

•	If possible, save the oscilloscope and application setup files as .set files

•	If possible, save the waveform on which you are performing the measurement as a .wfm file

Once you have gathered this information, you can contact technical support by phone or through e-mail.  If using e-mail, be sure to enter in the subject line "TDSDDM2 Problem," and attach the .set and .wfm files.

To include screen shots, from the oscilloscope menu bar, select File> Export….  The Export Dialog box displays.  Enter a file name with a .bmp extension and Save.  The file is saved in the C:\TDS7000\Images directory.  You can then attach the file to your email (depending on the capabilities of your email editor).


Using Online Help

Online help has many advantages over a printed manual because of advanced search capabilities.  Selecting Help on the right side of the application's Menu bar brings up the help file.

The main (opening) Help screen shows a series of book icons and three tabs along the top menu, each of which offers a unique mode of assistance:

•	Table of Contents (TOC) tab - organizes the Help into book-like sections.  Click a book icon to open a section; select any of the topics listed under the book.

•	Index  tab - enables you to scroll a list of alphabetical keywords. Click the topic of interest to bring up the appropriate help page.

•	Find tab - allows a text-based search.  Follow these steps:

1.	Type the word or phrase you wish to find in the search box.

2.	Select some matching words in the next box to narrow your search.

3.	Choose a topic in the lower box, and then click the Display button.

•	To print a topic, select the Print button from the help topics menu bar (To print color example screens, see Color Printing.)

•	Select Options from the menu bar for other commands, such as to annotate a topic, keep the help window on top or to use system colors.

•	Select the Back button to return to the previous help window.  Sometimes you can jump from one topic to another through a hyperlink. If the Back button is "grayed out" or a jump is not available, choose the "Help Topics" button to return to the originating help folder.

•	Browse buttons (Next >> and Previous <<) allow you to move forward and backward through  topics in the order of the Table of Contents (TOC).

•	Sometimes you will see the bolded word, "Note," in topic text.  This indicates important information.

Note:

Certain aspects of the online help are unique to applications that run on the oscilloscope.

Green text  (with dotted underline) indicates a "Popup."  Click the green text to display a brief help message. Click to return to the topic.

Green-underlined text indicates a Jump (hyperlink) to another topic. Select the green text to jump to the related topic. For example, click the green text to jump to the topic on Online Help and Related Documentation.

You can tell when the cursor is over an active hyperlink (button, jump, or popup), because the cursor "arrow" changes to a small "hand."

Note the "light bulb" and word "Tip" in the graphic above.  This graphic indicates additional information to help you function faster or more efficiently.


Color Printing

Some online help topics have color in the examples of the displayed application. If you want to print this type of topic on a monochrome printer, some information may not print because of certain colors. Instead, you should print the topic from PDF (portable document format) file that corresponds to the Online Help. You can find the file in the Documents directory on the Optional Applications Software on a Windows-Based Oscilloscope CD. The figures of application menus in the PDF file are gray scale and all of the information prints.


Popup Box

This is a Popup.


Product Description

The TDSDDM2 Disk Drive Measurements Application is a Java–based application that enhances basic capabilities of some Tektronix oscilloscopes.

The application provides disk drive measurements, can display the results as statistics or as a plot, and can save the results to a data log file.

The figure below shows an example of statistical results for a TAA measurement in the application part of the display (lower half) and a Track Profile plot of those results in the oscilloscope part of the display (upper half).

TDSDDM2 Disk Drive Measurements Application

Note:

There are no standard accessories for this product other than the manual.

What do you want to do?

Check Compatibility

Look Over Requirements and Restrictions

Go to Installation


Compatibility

For information on oscilloscope compatibility, refer to the product data sheet (use the Search tool on the www.tektronix.com web site) or the Optional Applications Software On Windows- Based Oscilloscopes Installation manual Tektronix part number 071-1888-XX. The manual is also available as a PDF file.


Requirements and Restrictions

The Sun Java Run-Time Environment V1.4.2 or above must be installed on the oscilloscope to operate the TDSDDM2 application.

The TDSDDM2 application does not support hard disk drives that mark the beginning of a track by the absence of a sector pulse.

Note: This application may be compatible with future models of oscilloscopes that have different specifications.  If this occurs, menus or options that are unavailable will appear dim if they are beyond the acquisition capability of the oscilloscope.


Accessories

There are no standard accessories for this product other than the manual.

To connect the Read Signal input to an oscilloscope channel, Tektronix Differential Probes are recommended, such as the P6247 or P6248 probe for TDS7054 and TDS7104 oscilloscopes, or the P7330 probe for a TDS7404 oscilloscope.


Installation

Refer to the Optional Applications Software on a Windows-Based Oscilloscope Installation Manual for the following information:

•	List of applications, compatible oscilloscopes, and relevant software and firmware version numbers

•	Applying a new label

•	Installing an application

•	Enabling an application

•	Downloading updates from the Tektronix Website

If you need to locate the corresponding Portable Document Format (PDF) file of this document, you can find it in the Documents directory on the Optional Applications Software on a Windows-Based Oscilloscope CD. The CD booklet only contains information on installing the application from the CD and on how to apply a new label.


Connecting to a System Under Test

For best signal accuracy, you should use one differential probe and two standard probes.  For connection to the Read signal, use a differential probe, such as the Tektronix P6247 or P6248 probe for the TDS7054 and TDS7104 oscilloscope, or the P7330 probe for the TDS7404 oscilloscope. For connection to the Index and Sector signals, use standard oscilloscope probes, such as the Tektronix P6139A passive probe or P6243 active probe for the TDS7054 and TDS7104 oscilloscope, or the P7240 active probe for the TDS7404 oscilloscope.

The table below shows the default channel–to–signal assignments. You can change the channel assignments to match your configuration.

Note: The TDSDDM2 application does not support disk drives that mark the beginning of a track by the absence of a sector pulse.  For this case, a timeout trigger setup is needed to identify the beginning of the track.

There are two connection configurations, primary and secondary.

WARNING: To avoid electric shock, you must ensure that power is removed from the SUT before attaching a probe to it. Do not touch exposed conductors except with the properly rated probe tips. Refer to the probe manual for proper use.

Power down the SUT before connecting probes to it.

See Also

Primary Setup

Secondary Setup


Primary Setup

Use the primary setup if you want the oscilloscope to control the disk measurements. The primary setup is used for most configurations. Connect the disk drive to the oscilloscope as shown below.

See Also

Secondary Setup


Secondary Setup

When using the secondary setup, you must specifically program the test measurement control sequences. Refer to the GPIB Program Example and to the  GPIB Command Syntax topics for more information on how to control the application with a GPIB program.

Connect the disk drive to the oscilloscope as shown below.

See Also

Primary Setup


SUT

System under test.


Configuring the Application

There are configuration tasks that you should perform before you start taking measurements. For the most part, these tasks configure the oscilloscope and Disk Drive Measurements Application to correctly acquire the signals from the disk drive under test.

These tasks are:

Setting Up the Oscilloscope Trigger

Setting Up the Application Trigger

Hysteresis

Configuring the Input Waveforms

Note:

You can find more information on setup parameters for specific measurements in about application parameters.


Setting Up the Oscilloscope Trigger

If you use the Read Gate, User or Index Trigger mode, you must manually set up the trigger. To do so, follow these steps:

1.	Connect the Index, Sector, and Read signals to Ch 4, Ch 3, and Ch 1 respectively.

2.	Go to Math in the oscilloscope menu bar and select Spectral Controls > T tab.

View the Spectral Control T Tab.

3.	Use the Multipurpose (MP) knobs to set the Sample Rate to 500 MS/s, 1.25 GS/s, 2.5 GS/s, 5 GS/s, or 10 GS/s.

4.	Use the MP knobs to set the Record Length to 50,000, 100,000, 200,000 or 400,000.

5.	For NLTS measurements, set the Record Length to at least 200,000.

6.	Set up the trigger:

a.	Go to Trig in the menu bar, access the A Event (Main) Trigger Setup menu, select the A Event tab, and set the Coupling to DC.

b.	Set the Slope to the appropriate edge for your disk drive signals, rising or falling.

c.	Set the Level to an appropriate level for your disk drive signals, or select Set 50%.

d.	Select the Mode tab, and set the Trigger Mode to Normal.

e.	Set the Holdoff to Auto.

See Also

Configuring the Application

Setting Up the Application Trigger

Hysteresis

Configuring the Input Waveforms


Spectral Control T Tab


Setting Up the Application Trigger

Before you begin to take measurements, you should specify the following trigger parameters:

•	Trigger mode, which selects the input trigger signal

•	Start Sector and Stop Sector (used with the Sector Trigger mode only), which specifies the range of sectors to be measured

•	Preamble (used with the Sector Trigger mode only), which the application uses to avoid acquiring the preamble

Set up the trigger parameters as follows:

1.	Start the application. The way you start the application depends on the oscilloscope model. To start the application do one of the following:

•	Select File > Run Application > Disk Drive Measurements 2 in the oscilloscope menu bar.

•	Select App > Disk Drive Measurements 2 in the oscilloscope menu bar.

•	Select Analyze > Disk Drive Measurements 2 in the oscilloscope menu bar.

2.	Select Inputs> Input/Trigger and select one of the following Trigger Modes:

Note: If you select the Read Gate, User, or Index Trigger mode, you must manually set up the oscilloscope trigger as described in the topic, Setting Up the Oscilloscope Trigger.

3.	For the Sector Trigger Mode, use the MP knob (or keypad) to select values for the Start Sector and Stop Sector options.

View Inputs/Trigger menu.

Note: The A -> B Seq trigger has a minimum count setting of 1.  If you want to trigger on sector 0, you must enter the value of N, where N is the total number of sectors on the track. The first Sector Pulse after the Index Pulse is sector 1.

The following figure shows how the sectors are numbered with respect to the B Event trigger in the oscilloscope application.

4.	For the Sector Trigger Mode, set the Preamble option. Use the MP knob (or keypad) to select a value that is greater than the actual signal preamble duration. This ensures that the application does not acquire the preamble and excludes it from the measurement.

See Also

Configuring the Application

Setting Up the OscilloscopeTrigger

Hysteresis

Configuring the Input Waveforms


Inputs/Trigger Menu


Hysteresis

Many of the measurements search for a local event called a peak and trough pair. You can set the hysteresis level so that noise will not cause false identification of peaks in the Read waveform. For a peak or trough to be found, the signal must be greater than the hysteresis level.

The application uses the value of the Hysteresis option in many measurements, such as TAA, PW50, Asymmetry (for TAA Snapshot and PW50 Snapshot measurements), Overwrite, Resolution, and Baseline Shift.  The figure below illustrates the use of hysteresis to avoid false identification of peaks.

To set the hysteresis levels, follow these steps:

1.	Select Inputs > General.

2.	Use the multipurpose knob (or keypad) to select a value in the Hysteresis option.

View Hysteresis option.

The units for hysteresis are in divisions.  The application uses the value for both the positive hysteresis level and the negative hysteresis level. For example, if you select a value of 2 divisions, the hysteresis levels are set to +2 divisions and -2 divisions above and below the waveform baseline.

See Also

Configuring the Application

Setting Up the OscilloscopeTrigger

Setting Up the Application Trigger

Configuring the Input Waveforms


Hysteresis Option


Configuring the Input Waveforms

Your configuration may not match the TDSDDM2 waveform assignments.The following table lists the Default channel assignments:

Note: Oscilloscope channels (Ch1, Ch2, Ch3, and Ch4) connect to real, live signals (waveforms) as opposed to waveforms that have been saved as .wfm files and can be recalled into reference memory (Ref1, Ref2, Ref3, and Ref4).

If necessary, you can reconfigure the input waveforms to match your disk drive configuration. To do so, follow these steps:

1.	Go to the Inputs menu in the menu bar and select Input/Trigger.

View the Inputs/Trigger menu.

2.	Use the list box for each signal and select the waveform that matches your configuration.

See Also

Configuring the Application

Setting Up the OscilloscopeTrigger

Setting Up the Application Trigger

Hysteresis


About Basic Operations

This section contains information on the following topics and tasks:

Application interface

Using basic oscilloscope functions

Setting up the application

Taking measurements

Analyzing the results

Saving the results to a file

Viewing a data log file

Saving and recalling setups

Exiting the application


Application Interface

The application uses a Windows interface.

View application interface (Measurements Menu)

Display Application Interface menu controls used to operate the application.

Note:

The oscilloscope application shrinks to half size and appears in the top half of the display when the application is running.


Measurements Menu


Application Interface Menu Controls


Using Basic Oscilloscope Functions

You can use the Help menu to access information about the oscilloscope. You can also use other oscilloscope functions and easily return to the application.

The application includes Online Help about the application menus and controls.

To display the Online Help, follow these steps:

1.	Choose the Help menu from the TDSDDM2 menu bar.

2.	Use the Contents, TOC, or Index tabs to navigate through the help.

See Also

Minimizing and Maximizing the Application

Returning to the Application

Using Online Help


Minimizing and Maximizing the Application

The application remains displayed when you minimize the oscilloscope. To minimize the application, select Measurements > Minimize or click the Hide button in the application.

The way you maximize the application depends on the oscilloscope model. To maximize the application do one of the following:

•	Select the App > Restore Application on the oscilloscope menu bar.

•	Select the Analyze > Restore Application on the oscilloscope menu bar.

•	Click the App button on the top right of the oscilloscope.


Returning to the Application

When you access oscilloscope functions, the oscilloscope fills the display. You can access oscilloscope functions in the following ways:

•	Select the Exit button in the application display

•	Choose the Menu-bar or Toolbar mode on the oscilloscope and access menus

•	Press front-panel buttons

To return to the application, choose the App button on the Top menu bar of the oscilloscope.


Menu Bar


Application Directories and File Names

The application uses directories to save and recall setup files and uses extensions appended to file names to identify the file type.

The following table lists default directory names.

See Also

File Name Extensions


Setting Up the Application

You can set up the application to take disk drive measurements from the SUT, you can plot the results, and you can save the statistical results to a data log file.

See Also

Selecting a Measurement


Selecting a Measurement

You can set up the application to take disk drive measurements from the SUT, you can plot the results, and you can save the statistical results to a data log file.

There are four Measurements menu items. Two allow you to select and configure a measurement, one allows you to save and recall measurement setups, and one allows you to minimize the application.

To access the TAA/PW50 Measurements menu, go to the Measurements menu in the menu bar and choose TAA/PW50.  View TAA/PW50 Measurements menu.  You may also wish to Display TAA/PW50 measurement options for a list of options and a description of each.


About TAA/PW50 Measurements

TAA (Track Average Amplitude) averages peak-to-peak values of data from a read waveform.  PW50 or Pulse Width at 50% measures the average pulse width at 50% of the peak value and includes both peaks and troughs.

See Also

TAA/PW50 Measurement Options

About the Limit Test


TAA/PW50 Measurement Options


About the Limit Test

Tests that enable Pass/Fail results and other limits can be set in some measurements.

See Also

Limit Test Area

Limit Test Entry Methods


Limit Test Area

The following table lists options in the Limit Test area with a brief description of each. For some measurements, such as TAA, PW50, Overwrite, Resolution, and Baseline Shift, these are the only options.

See Also

Limit Test Entry Methods

TAA/PW50 Limit Test Area Parameters

NLTS/Other Limit Test Area Parameters


Limit Test Entry Methods

The two methods to enter values for the Limit Test are described below.

Display Entry Methods.


Entry Methods


About NLTS/Other Measurements

To access the NLTS/Other Measurements menu, go to the Measurements menu in the menu bar and select NLTS/Other.

View the NLTS/Other Measurements Menu.

See Also

NLTS/Other Measurements Options


NLTS/Other Measurements Menu


NLTS/Other Measurements Options


NLTS Parameter Options


Table of NLTS Parameter Options

Note: The application initially uses the estimated value that you enter for the Pattern Dur option. The application then uses autocorrelation to precisely measure the duration pattern and replaces the estimated value.

View NLTS parameter options

See Also

NLTS Parameters Area

How The Application Calculates the Polynominal Index


How The Application Calculates the Polynominal Index

The following figure shows an example of how the application uses x = 2 to calculate the polynominal index.


Table of SNR Parameter Options

View SNR parameter options

See Also

SNR Parameters Area

Measuring SNR


SNR Parameter Options


Identifying an Asperity Signal

The value for the Threshold option determines if the application identifies the signal as an asperity.

View Asperity parameter options.

See Also

Asperity Parameter Area


Asperity Parameter Options


Configuring a Measurement

There are three Inputs menus that allow you to configure the input waveforms for measurement.  To configure these inputs use Inputs/Trigger, Inputs/Filters, and Inputs General.


Inputs/Trigger

To configure the input waveforms for a measurement, go to the Inputs menu in the menu bar and choose Inputs/Trigger. View the Inputs/Trigger menu.

The application has the following Input Channels options:

•	Read Signal: a waveform that performs a read operation from a sector

•	Read Gate: a waveform that indicates the beginning of a read operation; the application Trigger mode must be set to Read Gate to use this input

•	Sector Pulse: a waveform that indicates the beginning of a sector; the application Trigger mode must be set to Sector to trigger with this and the Index Pulse inputs

•	Index Pulse: a waveform that indicates the beginning of a track; the application Trigger mode must be set to Index or to Sector to trigger with this input.

See Also

Configuring the Input Waveforms

Input Channels Area Parameters

Trigger Options


Trigger Options

Note: For more information on how the application Trigger modes affect the oscilloscope trigger controls, refer to step 2 of Setting Up the Application Trigger.

View the Inputs/Trigger menu.

See Also

Setting Up the Oscilloscope Trigger

Trigger Area Parameters


Filters

You can modify the Read Signal input by applying filters that block specific frequency bands.  You can configure each filter as either a Highpass to block out the low frequency band, or as a Lowpass to block out the high frequency band.  You can also configure the filters by selecting Slope and a Cutoff Frequency based on the sample rate.

To configure a filter for a measurement, go to the Inputs menu in the menu bar and choose Filters.  View the Inputs Filters menu.

See Also

Filter characteristics of various filter options

Options for Filter 1 and Filter 2 with a brief description of each

Filtering Transient Responses

Cutoff Frequency and Sample Rates

Using both Highpass and Lowpass filters


Inputs Filters Menu


Cutoff Frequency and Sample Rates

When you start the application, or recall the default setup, the application uses the current oscilloscope sample rate to calculate a Min and Max range for Cutoff Frequency values.  The Min and Max range displays at the bottom of the Inputs Filter menu.  the application also sets the Lowpass filter to 15% of the sample rate and the Highpass filter to 10%.  You can adjust the Cutoff Frequency value within the Min and Max range.

When you change the sample rate and choose the Update command button, the Min value is set to 5% of the sample rate and the Max value is set to 35% for both filters. The application retains the value of the Cutoff Frequency if it is within the updated range. If the value is outside the updated range, the application adjusts the Cutoff Frequency to the closest value within the updated range.

Note:  If the value of the Cutoff Frequency is below the updated range, the application sets it to the Min value. If the value is above the updated range, the application sets it to the Max value.

See Also

How to change the sample rate and adjust filter frequencies.


How to Change the Sample Rate and Adjust Filter Frequencies

To change the sample rate and adjust the filter frequencies, follow these steps:

1.	Use the Horizontal Scale knob on the oscilloscope to change the sample rate.

2.	Choose the Update command button for either filter. The Min and Max values for both filters change relative to the new sample rate.

3.	Adjust the Cutoff Frequency option according to your needs.


Filters Options

See Also

Inputs Filters Area Parameters


Filter Characteristics


Using Both Highpass and Lowpass Filters

When you use both filters, the application first applies Filter 1 to the Read Signal input and then Filter 2.  You should be aware that you could select a Cutoff Frequency value that filters out the entire waveform or all but a small amount of noise.  The figure below shows the spectrum of the waveform passed to take measurements when you use both the Highpass and the Lowpass filters.


Inputs General

To configure the hysteresis or the gating for a measurement, go to the Inputs menu in the menu bar and choose General.  View the Inputs General menu.

See Also

Inputs General Options


Inputs General Menu


Inputs General Options

See Also

Inputs General Menu Parameters


Filtering Transient Responses

At the beginning and end of the filtered waveform, there will be a transient response caused by response of the filter to a discontinuity.  You can use Gating in the Inputs General menu to exclude the discontinuity from measurement calculations. To do this, follow these steps:

1.	Select Inputs > Filters > On > Store In and the desired reference memory, Ref1, Ref2, Ref3, or Ref4.

2.	Select Single Mode and press [image] to start the measurement sequence.

3.	Remove the Read Signal input waveform from the display.  If the input is a channel, press the front-panel channel button to remove the waveform.

4.	Observe the displayed Ref waveform and verify that the amplitude is correct.

You can see transient responses at the beginning and the end of the waveform.

5.	Select Inputs > General > Gating > On.

6.	Move the vertical cursors so that there are no transient responses between them; this excludes the transient responses from the measurement.

7.	Press [image] to start the measurement sequence.

8.	Repeat step 3 to remove the Read Signal waveform from the display.

9.	Observe the displayed Ref waveform.  If necessary, adjust the Cutoff Frequency value; steeper slopes yield longer transient responses.

10.	If necessary, repeat step 6.

11.	Select Inputs > Filters > Store In > None.  The application will display measurement results faster when reference memories are not used.


About Taking Measurements

If you want to change trigger settings or localize the measurement, you should do so before you take any measurements.

Note:

If you select a reference or math waveform as the source, you will need to recall and display the waveform before the application can take a measurement. For an example from the tutorial on how to do this, refer to Recalling a Waveform File.

Remember to select Reset to set the results to zero if you change the oscilloscope Vertical or Horizontal time settings between measurements.


Acquiring Waveforms

To acquire data from waveforms, follow these steps:

1.	Select a Sequence mode. Display the Sequence Control Menu Options.

Note: The Sequence Control menu is always accessible in the right side of the application display. View Sequence Control menu..

2.	Press the [image] to start the acquisition.

Note:

Do not change oscilloscope settings while taking a measurement, since this can cause an invalid measurement.


Sequence Control Menu Option/Buttons

View Sequence Control Menu.

See Also

Sequence Control Menu Parameters


Sequence Control Menu


Localizing Measurements

By specifying the trigger position, the starting point, and the length of the waveform, you can effectively filter out information that is not useful to analyze before taking a measurement. Refer to setting up the oscilloscope trigger for information on how to adjust the Record Length and the Sample Rate in the Math > Spectral Controls menu (T tab) in the oscilloscope application.

There is an alternative method to control the amount of data to measure without using gated cursors or specifying a range of sectors. You can do this by adjusting the Preamble Duration in the application Sector menu and the Record Length or Horizontal Scale in the oscilloscope horizontal menu. By specifying both the starting point and the total length of the measurement in this way, you can effectively size the area of interest.

Note:

If an error message displays because there are not enough cycles from which to take a measurement, you should increase the Record Length or the Horizontal Scale.


Analyzing the Results

You can view the results as statistics or graphically as a plot.  Display an example of results as a Track Profile plot.

Note:  Stop the acquisition before viewing the results as plots if you are taking measurements in the Free Run mode.

You can also log the data to a "csv" file for viewing in a spreadsheet, database, text editing or data analysis program.

View example of how a "csv" file may look in a spreadsheet program.

Note:  Statistical results vary widely across the different measurements.  Because of this, each measurement has a unique format for the statistics in a log file.

See Also

Viewing Statistics

Clearing Results


CSV Spreadsheet Example


Viewing Statistics

To access the View Results menu, go to the View menu in the menu bar and choose Results. Refer to the Applications Examples section to see examples of statistical results for each type of measurement.

The statistical information that displays will vary by measurement. In general, the View Results menu contains statistical values for the mean,  the maximum (Max), the minimum (Min), the standard deviation (StdDev), the SNR statistics (StatSNR), the number of peaks, troughs or peak/trough pairs used for the average values (num avg), and the sector number.


Viewing Plots

There is one plot format: Track Profile. The format plots the results such that the vertical axis represents the mean measurement value and the horizontal axis represents the measurement number.

To access the Plot Track Profile menu, go to the Plots menu in the menu bar and choose Track Profile.  View the Plot Track Profile menu.

See Also

Plot Track Profile Options


Plot Track Profile Menu


Plot Track Profile Options

When the application trigger mode is set to Sector, the Plot Track Profile menu also contains the following readouts:

•	Value at Cursor displays the measurement value and is in units relative to the measurement (V, Mhz, dBs).

•	Sector at Cursor displays the measurement number or the sector number at the cursor

For more information on Track Profiles, see Creating and Viewing Track Profile Plots.

See Also

Plot Track Profile Menu Parameters


Clearing Results

To reset the results to zero, choose the Reset button on the Sequence Control menu.  You do not have to wait for a measurement to complete to clear the results.


Saving (Logging) Results to a File

You can save (log) the results for all active measurements as statistics to a data log file.

Note: The application does not log results from the Overwrite or the Resolution measurements.

See Also

How to save the Results to a Data Log File


Logging Statistics

Logging saves the statistical results from measurements to a data log file. To access the Log Statistics menu, go to the Log menu in the menu bar and choose Statistics.

View the Log Statistics menu.

See Also

Log:  Statistics Options and Buttons


Log:  Statistics Options and Buttons

View the Log: Statistics Menu.

See Also

Example of Log file directory that displays when you select Browse

Log Statistics Menu Parameters


Saving the Results to a Data Log File

To save the measurement results to a data log file, follow these steps:

1.	Go to the Log menu in the menu bar and select Statistics.

     Display the statistics options and buttons.

2.	Select Logging On.

3.	Press [image] to start the acquisition.

4.	After the measurement completes, press the Acquire button again to log more data to the results.csv file.

5.	Select Logging Off before viewing the data log file.

See Also

Viewing a Data Log File

Data Log File Format


Log: Statistics Menu


Log File Directory


Data Log File Format

The data log file consists of one header row and rows of logged information. The header row contains the application name, the version number of the application, and the date and time on which the file was created. The remaining rows contain information for the measurements. The information will vary with the measurements being logged.

Note:

If you are using a GPIB program to execute the application, such as in automated test environments, you can add your own annotation through the logAnnotate GPIB command. You can add information consisting of up to 20 characters; the custom information will appear after the date and time in the rows of logged data.

See Also

Saving the Results to a Data Log File


Viewing a Data Log File

You can view the .csv data log file (comma separated variable format) in a spreadsheet, database, text editing or data analysis program for further analysis.

You must take measurements in Free Run mode to accumulate data points and store them in one data log file.  Display a spreadsheet example of a data log file (csv).

You can use Notepad or Wordpad to quickly view the results in the data log file.


How to Save and Recall Setups

You can use the Save/Recall Measurements menu to save and recall different configuration setups. To access the Save/Recall Measurements menu, go to the Measurements menu in the menu bar and choose Save/Recall.  View the Save/Recall Measurements menu.

You may also wish to display the Save/Recall Measurement Options.

Note:

The Measurements > Save/Recall function includes the settings of the oscilloscope application. When you exit the application, you can choose whether to restore the settings of the oscilloscope to those present before starting the application.

Caution: Do not edit the .ini or the .set files, or recall setup files not generated by the application, since this can cause the application to become unstable.

See Also

Saving a Setup

Recalling a Saved Setup

Recalling the Default Setup


Save/Recall Measurements Menu


Save/Recall Measurement Options

View Save/Recall measurements menu.

Note:

The Measurements > Save/Recall function includes the settings of  the oscilloscope application. When you exit the application, you can choose whether to restore oscilloscope settings to those present before starting the application.

Do not edit the .ini or the .set files, or recall setup files not generated by the application, since this can cause the application to become unstable.

See Also

Save/Recall Menu Parameters


Saving a Setup

To save the application settings to a setup file, follow these steps:

1.	Select Measurements > Save/Recall.

2.	Select the Save button.

3.	Select the directory in which the setup file will be saved.

4.	Select or enter a file name.  The application appends an ".ini" extension to the name of setup files.

5.	Choose Save.

Note:

The application also saves the oscilloscope setup to a ".set" file when you save an application setup.  Both the application ".ini" file and oscilloscope ".set" file have the same file name.

See Also

Recalling a Saved Setup

Recalling the Default Setup


Recalling a Saved Setup

To recall the application and oscilloscope settings from a saved setup file, follow these steps:

1.	Select Measurements > Save/Recall.

2.	Select the Recall button.

3.	Select the directory from which the setup file will be recalled.

4.	Select or enter a setup file name.

5.	Choose Recall.

Note:

The application also recalls the oscilloscope setup from a ".set" file when you recall an application setup.


Recalling the Default Setup

To recall the application settings from the Default setup file, follow these steps:

1.	Select Measurements > Save/Recall.

2.	Choose Recall default values.


Exiting the application

To exit the application, choose Exit. When you exit the application, you can select to keep the oscilloscope setup currently in use with the application or to restore the oscilloscope setup that was present before you started the application.


Select Active Measurements Menu


File Name Extensions


Trigger

In measurement terms, a trigger event occurs when voltage measured passes through a specific level on the specified slope or edge.  See the oscilloscope online help for more information.


Population

 The number of samples used to calculate the statistics.


Acquire or Start Button

Selecting this button, starts a the acquisition of data for a measurement.


Introduction to the Tutorial

This tutorial teaches you how to set up the application, take a measurement, view the results, and log the results. See the topic, About Basic Operations, for more operating information.

Before you begin the tutorial, you must do the following tasks:

•	Set up the oscilloscope

•	Start the application

•	Recall a waveform file

Note: Displays of an oscilloscope are from a TDS7104 model; there may be minor differences in the displays from other types of oscilloscopes.


Setting Up the Oscilloscope

To set up the oscilloscope, follow these steps:

1.	Go to the File menu in the menu bar and select Recall Default Setup to set the oscilloscope to the default factory settings.

2.	Press the individual CH 1, CH 2, CH 3, and CH 4 buttons as needed to remove active waveforms from the display.


Starting the Application

To perform these lessons, the application must be installed and enabled on the oscilloscope. See installation procedure.

The way you start the application depends on the oscilloscope model. To start the application do one of the following:

•	Select File > Run Application > Disk Drive Measurements 2 in the oscilloscope menu bar.

•	Select App > Disk Drive Measurements 2 in the oscilloscope menu bar.

•	Select Analyze > Disk Drive Measurements 2 in the oscilloscope menu bar.

 View the application startup menu.


Application Startup (Measurements) Menu


Recalling a Waveform File

The application includes a TAA waveform that you can use with this tutorial. The taapw50.wfm file is from a Read Signal.

To recall the taapw50.wfm file to Ref1 on to the oscilloscope, follow these steps:

1.	Go to the File menu in the menu bar and access Reference Waveforms> Reference Setup. Display oscilloscope refrence waveform setup.

2.	Select the Ref 1 tab and Recall.  Choose the c:\TekApplications\tdsddm2\waveforms directory. Display a list of  the waveform files that appear.

3.	Select the taapw50.wfm file and select Recall.

4.	To return to the application, choose the App button in the Menu bar.


Oscilloscope Reference Waveform Setup


Reference Waveform Files Directory


Taking a TAA Measurement

In this example, you will learn how to use the application to take a Track Average Amplitude (TAA) measurement. To take a TAA measurement, refer to the Inputs/Trigger menu setup below and follow these steps:

1.	Select Inputs> Input/Trigger> Input Channels> Read Signal> Ref 1.

2.	Press [image] to start the acquisition.

Display TAA lesson statistical results.


TAA Lesson Statistical Results


How to Save the Results to a Data Log File

To save the measurement results to a data log file, follow these steps:

1.	Go to the Log menu in the menu bar and select Statistics.

Display an example of the default application directory and log file name.

2.	Select Logging On.

3.	Press [image] to start the acquisition.

4.	Select Logging Off before viewing the data log file.

5.	Exit the application.


Log Statistics Menu with Default File Name


How to View a Data Log File

To view the data log file in a text editing application, such as Wordpad, follow these steps:

1.	From the tool bar, select Start icon> Programs> Accessories> Wordpad.

2.	Select File> Open.

3.	Locate the C:\TekApplications\tdsddm2\data directory.

4.	Select All Documents (*.*) for the Files of Type.

Display Log file with default file name.

5.	Select the TAA.csv file and Open.

Display example of TAA.csv file viewed in Wordpad.

You can also import the .csv file to a DOS–based personal computer and then view the data log file with a spreadsheet, database, or data analysis program.


Log File


TAA.csv File Viewed in Wordpad


Stopping the Tutorial

If you need more than one session to complete the tutorial lessons, you can stop the tutorial and return to it another time.

To save the application setup and stop your session, refer to Saving a Setup.


Returning to the Tutorial

To return to the tutorial setup, you can start the application and then recall the saved setup. To recall the application setup, refer to Recalling a Saved Setup.


About Application Examples

This section presents many application examples. The simplified examples highlight the application measurements and give you ideas on how to use the application to solve your own test problems.

To use these examples, you must have the TDSDDM2 application installed and enabled on the oscilloscope, the probes connected to your disk drive system under test (SUT), and the configuration tasks performed as needed for your SUT. For information, see Installation procedures and Configuring the application. See also Starting the application.

See Also

Waveform Files for Use with Application Examples

Measuring TAA

Measuring PW50

Measuring Asperity

Measuring Overwrite

Measuring Resolution

Measuring Baseline Shift

Measuring NLTS

Measuring SNR

Creating and viewing track profiles


Waveform Files for Use with Application Examples

The application includes waveform files that you can recall to a reference memory to try out each example in this section. The following table lists the waveform file names and corresponding measurements.


Measurement Configurations

You can configure any measurement to help you analyze measurement results. The application includes the following possible configurations:

•	Specifying a Range of Sectors

•	Specifying a Limit Test

•	Specifying Gating

•	Specifying hysteresis

•	Specifying a Filter


Specifying a Range of Sectors

To specify a range of sectors from which to take measurements, follow these steps:

1.	Select Inputs> Inputs/Trigger > Trigger Mode > Sector.

2.	Select Start Sector > (number).

3.	Select Stop Sector > (number).

4.	Set the Preamble option. Use the multipurpose knob, and select a value that is greater than the actual signal preamble duration. This ensures that the preamble is not acquired and is not included in the measurement.


Specifying a Limit Test

To use limit testing to include a pass/fail measurement result, follow these steps:

1.	Select Limit Test On.

2.	Use the multipurpose knob to set a value for the Upper Limit option that is appropriate for your SUT.  View Entry Methods menu showing multipurpose knob.

3.	Use the multipurpose knob to set a value for the Lower Limit option that is appropriate for your SUT.

The Asperity measurement does not need to test limits.


Specifying Gating

Instead of measuring around the entire track, you can use cursor gating to localize the measurement. To specify gating, follow these steps:

1.	Select Inputs> General > Gating On.

2.	In the oscilloscope program, position the cursors to bound the part (on either side) of the waveform that you want to measure.

3.	Select App to return to the application.


Specifying Hysteresis

You can use the Hysteresis option to avoid identifying noise as actual signals.

To specify hysteresis, select Inputs/General > Hysteresis and use the multipurpose knob to set a value for the Hysteresis option that is appropriate for your SUT.

The hysteresis value, in divisions, is reflected above and below the waveform baseline. For example, if you choose a value of 1.5 divs, the hysteresis level ranges from -1.5 divs to +1.5 divs.


Specifying a Filter

You can modify the Read Signal input by applying filters that block specific frequency bands.

See Also

Filters


Using Reference Waveforms

To attain the results shown in each figure (except for Track Profile) from the specified .wfm file, you need to define the following general setup:

1.	In the oscilloscope menu bar, select File> Recall Default Setup.

2.	Recall the appropriate .wfm file to one of the reference memories; Display reference waveform files directory.

3.	Select Measurements> Save/Recall> Recall default values.

4.	Select the appropriate measurement from either the TAA/PW50 or NLTS/Other Measurements menus.

5.	Select the reference memory as the Read Signal input option in the Inputs/Trigger menu.

See Also

Waveform Files for Use with Application Examples

Measuring TAA

Measuring PW50

Measuring Asperity

Measuring Overwrite

Measuring Resolution

Measuring Baseline Shift

Measuring NLTS

Measuring SNR

Creating and viewing track profiles


Measuring TAA

In this example, you can measure the track average amplitude (TAA). To take a TAA measurement, follow these steps:

1.	Select Measurements > TAA/PW50 > TAA.

2.	To configure the measurement, refer to Configuring a Measurement.

3.	Set the Sequence Mode to Single or Free Run.

4.	Select [image] to start the measurement.

5.	When the measurement is complete, the statistical results automatically display.

Display an example of TAA measurement results based on the taapw50.wfm file.


Measuring PW50

In this example, you can measure the pulse width at 50% (PW50). To take a PW50 measurement, follow these steps:

1.	Select Measurements > TAA/PW50 > PW50.

2.	To configure the measurement, refer to Configuring a Measurement.

3.	Set the Sequence Mode to Single or Free Run.

4.	Select [image] to start the measurement.

5.	When the measurement is complete, the statistical results automatically display.

Display an example of PW50 measurement results based on the taapw50.wfm file.


PW50 Measurement Results Example


Measuring Asperity

In this example, the oscilloscope will detect asperities. To take an Asperity measurement, follow these steps:

1.	Select Measurements > NLTS/Other > Asperity.

2.	Use the multipurpose knob to set a value for the Threshold option that is appropriate for your SUT.

The recommended initial setting is at least twice the peak value of the signal. If the signal crosses this level, it is counted as an asperity. No additional asperities are counted until the signal crosses zero volts again.

3.	If you want to change trigger settings or localize the measurement, do so now. The application defaults to the settings specified in the Trigger menu. For further information, see Setting Up the Application Trigger.

4.	Set the Sequence Mode to Single.

5.	Select [image] to start the measurement.

6.	When the measurement is complete, a list of asperities, sector locations and time locations automatically display.

Display an example of Asperity measurement results based on the asperity.wfm file.

Note: To attain these results from the asperity.wfm file, in addition to the general procedure, you need to define the Asperity Threshold as 1.5 V.


Asperity Measurement Results Example


Measuring Overwrite

In this example, you can measure the overwrite amount of residual signal remaining from a previous write when new data is written to the same location. The application overwrites part of the disk drive to take this measurement.

To measure overwrite, you will also need a personal computer.

Note: Select a record length on the oscilloscope of 5,000 or more for Overwrite measurements. This increases the frequency and the measurement resolution.

To take an Overwrite measurement, follow these steps:

1.	Erase the track by using a permanent magnet or using the PC to perform a DC erase for many revolutions on a three-band track of overlapping tracks centered on the specified radius.

2.	Write a low–frequency data pattern of isolated pulses to the track.

To try out this example, recall the ovlosig.wfm file to a reference memory.

3.	Select Measurements> NLTS/Other> Overwrt.

4.	Set the Sequence Mode to Single or Free Run.

5.	Select [image] to start the measurement. The application measures the magnitude of the signal and then pauses.

The Sequence Control displays Paused For Action and the results display PASS 1 in the upper right corner.  Display an example of the Overwrite measurement Pass 1 results based on the ovlosig.wfm file

6.	Without erasing the previous data, overwrite the track with a high–frequency data pattern.

If you are trying out this example, you can overwrite the ovlosig.wfm file with the ovhisig.wfm file. To do this, recall the ovhisig.wfm file to the same reference memory used for the ovlosig.wfm file.

7.	Select [image] to continue. The results display PASS 2 in the upper right corner.

When the measurement is complete, the statistical results automatically display.

Display an example of the Overwrite measurement Pass 2 results based on the ovlosig.wfm and ovhisig.wfm files.


Overwrite Measurement, PASS 1 Example


Overwrite Measurement Results, PASS 2 Example


Measuring Resolution

In this example, you can measure the resolution of a head and disk combination. The application determines the ratio of two TAA measurements of a low–frequency pattern to a high–frequency pattern. The result is a percentage.

Note: To measure the resolution, you will also need a personal computer.

To take a Resolution measurement, follow these steps:

1.	Erase the track by using a permanent magnet or using the PC to perform a DC erase for many revolutions on a three-band track of overlapping tracks centered on the specified radius.

2.	Use the PC to write a high–frequency data pattern of isolated pulses to the disk.

3.	Select Measurements > NLTS/Other> Resltn.

4.	Set the Sequence Mode to Single.

5.	Select [image] to start the measurement. The oscilloscope performs a TAA measurement of the high–frequency pattern and then pauses.

6.	The Sequence Control displays Paused For Action and the results display PASS 1 in the upper right corner.

7.	Erase the track again as described in step 1.

8.	Use the PC to write a low–frequency data pattern of isolated pulses to the disk.

9.	Select [image] to continue. The results display PASS 2 in the upper right corner.

10.	When the measurement is complete, the statistical results automatically display.

An example is not included because it is similar to the Overwrite measurement.

See Also

Measuring Overwrite


Measuring Baseline Shift

In this example, you will measure the difference between the baseline of a positive pulse and the baseline of a negative pulse. To take a Baseline Shift measurement, follow these steps:

1.	Select Measurements > NLTS/Other > Baseline Shift.

2.	Set the Sequence Mode to Single or Free Run.

3.	Select [image] to start the measurement.

4.	When the measurement is complete, the statistical results automatically display. Figure 2-39 shows an example of a Baseline Shift measurement results based on the baseline.wfm file.

Display Baseline Shift measurement results example.


Baseline Shift Measurements Results Example


Measuring NLTS

To take NLTS measurements, your setup must meet the following requirements:

•	The waveform selected for the measurement must correspond to a bit pattern written on the disk generated using a valid (maximum length) polynomial; among other things, this might require that you disable RLL encoding.

•	The disk drive waveform must have at least 1,000 samples.

•	There must be at least eight samples per bit.

•	The oscilloscope must acquire at least three periods of the pattern where the period is the amount of time before the pseudo–random bit pattern begins to repeat itself; to do this depends on the sample rate of the oscilloscope, the estimated value that you enter for the Pattern Dur option, and the number of bits per period (based on the polynominal used).

To take an NLTS measurement, follow these steps:

1.	Select Measurements> NLTS/Other> NLTS Initial.

2.	Select Pattern Dur and specify a value.

The pattern duration is the length of time of the period of a pseudo–random data pattern in the readback signal. The pattern duration can be an estimate, as long as the estimate is within the tolerance that you specify in step 3; the application will measure the exact duration of the pattern. (Due to variations in revolution speed between disk drives, specifying the pattern duration is necessarily an estimate.)

3.	Select Dur Toler and specify the tolerance of your pattern duration estimate (up to 30%). Using a tighter tolerance reduces measurement time.

Note:  If you know the exact duration of the data pattern, you can reduce the measurement time by specifying a Duration Tolerance of 0%. The application will use the Pattern Duration that you specify without attempting to adjust to the actual duration of the pseudo–random pattern.

4.	Select Poly Index and use the multipurpose knob to specify the pseudo–
random binary sequence polynomial. This should be the same polynomial used to generate the data pattern written to the media.

For valid results, it is essential that you specify the same polynominial as the one used for recording data on the hard disk (media). Both polynomials must be valid according to the 1995 IDEMA "white paper."

The NLTS measurement is based on autocorrelation and uses a polynomial to generate a pseudo–noise sequence. Select the polynomial using the multipurpose knob; all selections provide a valid pseudo–noise sequence. (The application removes invalid polynomials from the selection set.) The polynomial index value on the scale is a condensed notation of the selected polynomial, obtainable by making x=2. For example:

5.	If you want to change trigger settings or localize the measurement, do so now. The application defaults to the settings specified in the Trigger menu. For further information, see Setting Up the Application Trigger.

6.	Set the Sequence Mode to Single or Free Run.

7.	Press [image] to start the acquisition.

8.	When the measurement is complete, the statistical results automatically display.

Display an example of NLTS Initial measurement results based on the x9x4x1.wfm file.


NLTS  Measurement Results Example


Measuring SNR

To take SNR measurements, your setup must meet the following requirements:

•	The disk drive waveform must have at least 1,000 samples

•	There must be at least eight samples per bit

•	The oscilloscope must acquire at least three periods of the pattern where the period is the amount of time before the pseudo–random bit pattern begins to repeat itself; to do this depends on the sample rate of the oscilloscope, the estimated value that you enter for the Pattern Dur option, and the number of bits per period

To take an SNR measurement, follow these steps:

1.	Select Measurements > NLTS/Other > SNR.

2.	Select Pattern Dur and specify a value.

The pattern duration is the length of time of the period of a pseudo–random pattern in the readback signal. The pattern duration can be an estimate, as long as the estimate is within the tolerance that you specify in step 3; the application will measure the exact duration of the pattern. (Due to variations in revolution speed between disk drives, specifying the pattern duration is necessarily an estimate.)

3.	Select Dur Toler and specify the tolerance of your pattern duration estimate (up to 30%). Using a tighter tolerance reduces measurement time.

Note:  If you know the exact duration of the data pattern, you can reduce the measurement time by specifying a Duration Tolerance of 0%. The application will use the Pattern Duration that you specify without attempting to adjust to the actual duration of the pseudo–random pattern.

4.	Select Bits/Pattern and specify a value.

Periodic signals used for the SNR measurement are isolated low–density periodic transitions (low frequency), isolated high–density periodic transitions (high frequency), or patterned data such as pseudo–random sequences.

•	If you are using a high–frequency pattern consisting of constantly spaced isolated transitions, use two bits per pattern for the low frequency and high frequency patterns.

•	For general patterned data, use the number of bits per pattern period, depending on what was previously recorded on the disk.

•	For pseudo–random data of pseudo–noise type generated with shift registers (pseudo–random binary sequence), the number of bits per pattern is 2L - 1, where L is the order of the characteristic polynomial. For example, for a 9th order polynomial the value would be [image]; for a 7th order polynomial the value would be [image].

5.	If you want to change trigger settings or localize the measurement, do so now. The application defaults to the settings specified in the Trigger menu. For further information, see Setting Up the Application Trigger.

6.	Set the Sequence Mode to Single.

7.	Press [image]  to start the acquisition.

8.	When the measurement is complete, the statistical results automatically display.

Display an example of SNR measurement results based on the x9x4x1.wfm file.


SNR Measurement Results Example


Creating and Viewing Track Profile Plots

Track Profile plots are reference memory waveforms that contain a history of measurement results. You can use track profiles to observe sector–to–sector variations in measurements and to identify the location of flaws within a track.

Note: The result of creating a Track Profile plot from a reference waveform is a short straight line.

To create and view a Track Profile plot, follow these steps:

1.	Select a measurement from either the TAA/PW50 or NLTS/Other Measurements menus.

2.	To configure the measurement, refer to Measurement Configurations.

3.	Select Inputs > General > Gating Off.

4.	Select Plot > Track Profile > Store Profile In:> any reference memory.

Note:  As soon as you select Plot> Track Profile> On, the application deletes all information contained in the selected reference memory.

5.	Select Plot > Track Profile > On.

6.	Set the Sequence Mode to Single or Free Run.

7.	Select [image] to start the measurement. The measurement results are saved as statistics and are stored as a track profile plot in the reference memory selected in step 4.

Display an example of a Track Profile plot from a TAA measurement.

8.	If you use the Sector Trigger mode (see Trigger Options), you can also use the vertical cursors on the oscilloscope.  To use the vertical cursors, press the Cursors front–panel button. The default Cursor Type is V Bars.

9.	Select App to return to the application.

You can view the results of each execution of the measurement algorithm by moving the cursor along the Track Profile plot. The Value at Cursor and Sector at Cursor readouts show the measurement results at the current location of the cursor. The Value at Cursor is in units relative to the measurement (V, MHz, dBs).

Note: The readout values are available only with current Track Profile plots; they are not available with waveforms that are recalled from reference memory.  You also must select the Sector Trigger mode to use cursors with track profiles.

Display an example Track Profile plot with cursors

10.	To save the reference waveform containing the plot, follow these steps:

a.	Go to the File menu in the menu bar of the oscilloscope and access Reference Waveforms > Reference Setup.

b.	Select the appropriate Ref tab and Save Wfm to File.

11.	To clear the Track Profile plot, select Reset.


Track Profile Plot Example


Track Profile Plot with Cursors


About Application Parameters

This section describes the TDSDDM2 application parameters, and includes the menu default settings. You should refer to the user manual for your oscilloscope for operating details of other controls, such as front–panel buttons.

The parameters for the menus and options list the selections or range of values available for each and also includes the default values.

Refer to the GPIB Programming section of this Help file for a complete list of the GPIB Command Syntax.  This entry includes a complete list of the GPIB commands along with the arguments, variables, and variable values that correspond to the TDSDDM2 parameters.

Note:

Incremental unit values shown are valid when the FINE button is enabled on the oscilloscope.


Measurement Menus

There are four choices on the Measurements menu:

TAA/PW50

NLTS/Other

Save/Recall

Minimize


TAA/PW50 Menu

The options in the TAA/PW50 Measurements menu are:

•	TAA, default

•	TAA+

•	TAA-

•	TAA Snapshot

•	PW50

•	PW50+

•	PW50-

•	PW50 snapshot

See Also

TAA/PW50 Limit Test Area Parameters


TAA/PW50 Limit Test Area Parameters


NLTS/Other Menu Options

The options in the NLTS/Other Measurements menu are:

•	NLTS Initial

•	NLTS 1st Adj

•	NLTS 2nd Adj

•	NLTS Snapshot

•	SNR

•	Asperity

•	Overwrite

•	Resolution

•	Baseline shift


NLTS/Other Limit Test Area Parameters


Minimize Menu Parameters

There are no parameters for the Minimize function.


Save/Recall Menu Parameters


NLTS Parameters Area


SNR Parameters Area


Asperity Parameter Area


Input Channels Area Parameters


Trigger Area Parameters

See Also

Setting Up the Oscilloscope Trigger

Setting Up the Application Trigger

Trigger Options


Inputs Filters Menu Parameters


Inputs General Menu Parameters


View Results Menu Parameters

There are no parameters for the View Results Menu


Plot Track Profile Menu Parameters


Log Statistics Menu Parameters


Help Menu Parameters

There are no parameters for the Help Menu.


Sequence Control Menu Parameters


About Measurement Algorithmns

TDSDDM2 performs disk drive measurements. This section contains information about the algorithms used by the application to execute each measurement.

Unless specifically stated otherwise, all measurements in the Disk Drive Measurements Application are conducted in accordance with procedures specified in the International Disk Drive Equipment and Materials Association (IDEMA) Disk Drive Standard.

Note:

Refer to the Applications Examples section for information on how to perform each measurement. Each example includes a detailed procedure.

See Also

Oscilloscope Setup Guidelines

Calculating Statistics

About TAA Measurements

About PW50 Measurements

Other Measurements

Snapshot Measurements

Introduction to Track Profile Plots


Oscilloscope Setup Guidelines

For all measurements, use the following guidelines to set up the oscilloscope:

1.	The signal is any channel, reference, or math waveform.

2.	The vertical scale for the waveform must be set so that the waveform does not exceed the vertical range of the TDS oscilloscope.

3.	The time per division must be set small enough to capture sufficient waveform detail and avoid aliasing.

4.	Use a differential probe on the Read channel signal to reject noise and remove DC bias.


Calculating Statistics

The application calculates statistics for each selected measurement, and logs the statisitcs on a cycle–cycle basis in a fairly large waveform. The standard statistics are for the Maximum, Minimum, Mean, Standard Deviation, and Population.

The application continues to calculate statistics until you press the Reset button in the Sequence Control menu. This resets all values to zero.

See Also

Maximum Value

Minimum Value

Mean Value

Standard Deviation Value


Maximum Value

The application calculates this statistic using the following equation:

Max X = Highest value of X


Minimum Value

The application calculates this statistic using the following equation:

Min X= Lowest value of X


Mean Value

The application calculates this statistic using the following equation:


Standard Deviation Value

It may seem odd that the equation for the estimate of the Standard Deviation contains a 1/(N-1) scaling factor. If you knew the true mean of X and used it in place of the estimated mean , [image], then you would, in fact, scale by 1/N. But, [image] is an estimate and is likely to be in error (or bias), causing the estimate of the Standard Deviation to be too small if scaled by 1/N. This is the reason for the scaling shown in the equation. (Refer to Chapter 9.2 in A. Papoulis, Probability, Random Variables, and Stochastic Processes, McGraw Hill, 1991.)

The application calculates this statistic using the following equation:


About TAA Measurements

The Track Average Amplitude is the average peak–to–peak value of the data on the Read Signal input over the specified range of sectors.

IDEMA specifies the measurement to be over one complete track revolution.

See Also

TAA Measurement

TAA + and TAA - Measurements


TAA Measurement

The application calculates this measurement using the following equation:

Where: 	N is the number of positive and negative pulse pairs

Vpp is the peak–to–peak voltage

The application performs the measurement according to the following algorithm:

1.	Find all of the peak–to–trough pairs in the data area to be measured.

Find the peak by searching from the first crossing of the signal above the positive hysteresis level to the crossing of the signal below the negative hysteresis level. (See figure below.) Keep the maximum value over this range. Take one sample on either side of the maximum value and average the three values to obtain the positive peak value. This is done to remove noise bias which would otherwise occur.

2.	Search the range from the negative hysteresis crossing to the next positive hysteresis crossing; keep the minimum value. Take one sample on either side of the minimum value and average the three values to obtain the negative peak value.

3.	Average all measured peak–to–peak values. The result is the TAA value.

The following figure shows how a TAA measurement is defined.


TAA + and TAA - Measurements

The TAA+ measurement is the average positive peak value of the data on the Read Signal input over the specified range of sectors. The TAA-measurement is the average negative peak value of the data on the Read Signal input over the specified range of sectors.

The application calculates these measurements using the following equation:

Where: 	N is the number of positive or negative pulses

Vp is the peak (positive or negative) voltage

The baseline reference for measuring TAA+ or TAA- is zero volts.

The application performs the measurement according to the same algorithm used in the TAA measurement except only positive pulses are measured for TAA+ and only negative pulses are measured for TAA-.  The following figure shows how TAA+ and TAA- measurements are defined.


About PW50 Measurements

The PW50 measurement is the average pulse width at 50% of the pulse peak of a group of both positive and negative pulses. Peaks and troughs are measured. The baseline reference for measuring the peak or trough is zero volts. The figure below shows the definition of a pulse width at 50%.

The application calculates this measurement using the following equation:

Where: 	N is the number of positive and negative pulse pairs

PW is the pulse width at 50%

The application performs the measurement according to the following algorithm:

1.	Set the disk drive to the specified speed.

2.	Position the head to the desired gap, radius, and skew angle.

3.	Precondition the media service. (See the IDEMA standard, document T3–91, for information about preconditioning the media service.)

4.	Write the specified frequency at the specified current for one revolution of the disk.

5.	Measure the peak–to–peak analog amplitude of the Read Signal for one entire revolution, excluding all nonuniform segments, such as write splices, servo gaps, and header fields. Uses the hysteresis value when looking for peaks.

6.	Compute the track average amplitude around the entire track by summing up the peak–to–peak voltages of each plus and minus pulse pair. Divide the result by the number of pulse pairs.

7.	Perform the measurement by acquiring one segment at a time, measuring it, and combining all the results for the final value. To speed up the measurement process, you can specify a smaller region of each track segment to measure by using the cursors gating or by decreasing the record length.

This measurement requires you to specify the number of segments on the track to be tested.

8.	Use a value of 1/2 of the TAA value as the threshold level at which to measure the pulse width of each positive and negative pulse. Compute the average pulse width around the track for all pulses measured.

9.	Displays the results in the View Results menu, saves the results as a Track Profile plot in a reference memory, or logs the data to a file. (The results also display the standard deviation of the measurement for all pairs used.)  The figure below shows the basis for these measurements.

The pulses making up the tested group are selected by the following criteria:

•	There must be enough pulses around the recording track to provide an adequate statistical sample.

•	The spacing between pulses must minimize any interaction between the measured pulses.

See Also

PW50 + and PW50 - Measurements


PW50 + and PW50 - Measurements

The PW50+ measurement is the pulse width at 50% of the peak value of the pulse; only peaks are measured. The PW50- measurement is the pulse width at 50% of the trough value of the pulse; only troughs are measured.

The application performs the measurement according to the same algorithm used in the PW50 measurements except only positive pulses are measured for PW50+ and only negative pulses are measured for PW50-.  The following figure shows how PW50+ and PW50- measurements are defined.


About NLTS Measurements

The NLTS measurement calculates three types of nonlinear transition shift on the disk drive media as follows:

•	Initial magnetization (DC erased)

•	First adjacent transition

•	Second adjacent transition

The initial magnetization of the media can affect the position at which transitions (reverses in magnetization) are recorded. Initial magnetization is characterized by a delay in a transition, occurring when the new transition reverses the direction of the previous magnetization.

The second transition in a series of consecutive transitions is called the first adjacent transition. The first adjacent transition is characterized as follows: when write data requires transitions on consecutive data bits, the latter transition is shifted earlier in time. In other words, when one transition in a series occurs, then the following transition occurs earlier than it should.

All subsequent transitions in the series of consecutive transitions are grouped into the category called second adjacent transition. Second adjacent transitions are similar to first adjacent transitions. The difference is that the transitions are separated by two bit periods, not one.

When nonlinear transition shift can be characterized, its behavior can be mitigated with write pre–compensation.

There is no NLTS specification in the IDEMA standard. The NLTS measurement is based on a time domain cross–correlation method detailed in the IDEMA Test and Measurement Committee PRML Working Group Working Paper Nonlinear Distortion Measurement Techniques, September 1995.

See Also

NLTS Test Methodology

NLTS Initial Measurement

NLTS 1st Adjacent Measurement

NLTS 2nd Adjacent Measurement


NLTS Test Methodology

The NLTS measurement algorithm assumes that the acquired signal consists of a periodic signal and independent additive noise. The noise is assumed to be responsible for all the nonperiodic behavior of the acquired waveform.

The application performs the measurement according to the following algorithm:

1.	Acquire three or more cycles of the pseudo–random pattern sequence read from the disk drive.

2.	You specify the polynomial used to generate the waveform, the approximate duration of one period of the periodic signal captured in the waveform, and the tolerance of the approximation.

Note: The specified polynomial must generate a pseudo–noise (maximum length sequence, or the measurement will not proceed.

3.	(This step is not performed if you specify a Duration Tolerance of 0%.) Compute the actual cycle time and delay values. Cycle time is the period of time required for the  pseudo–random pattern until it begins to repeats itself.

NLTS guarantees that the real cycle time is determined by the measurement if your initial estimate for the cycle time is within the specified tolerance (up to 30%) of its real value.

The NLTS measurement uses several cycles of the pseudo–random pattern waveform to improve the accuracy of the measurement, averaging over multiple single–waveform–cycle NLTS values.


NLTS Initial Measurement

The NLTS initial magnetization measurement assumes the following sequence:

1.	The medium is initially magnetized in one direction (DC–erased)

2.	Transitions that are written by a head field in the opposite direction are shifted later by an amount [image].

The application calculates this measurement using the following equation:

Where: is the playback voltage for a readback channel affected by
     NLTS initial magnetization

   V(t) is the playback voltage in the absence of nonlinear effects

     T is the bit period

    is the amount of shift

                is an integer, whose unique value is determined by the
     polynomial used to generate the recorded pseudo–noise bit
     sequence

The measurement reports the nonlinear effect as a percentage of T; that is, [image].


NLTS 1st Adjacent Measurement

The NLTS first adjacent transition is the condition where the location of a transition is shifted earlier by an amount [image] due to another transition one bit interval earlier.

The application calculates this measurement using the following equation:

Where: 	is the playback voltage for a readback channel affected by
NLTS first adjacent transition

V(t) is the playback voltage in the absence of nonlinear effects

T is the bit period

is the amount of shift

is an integer, whose unique value is determined by the
polynomial used to generate the recorded pseudo–noise bit
sequence


NLTS 2nd Adjacent Measurement

The NLTS second adjacent transition is similar to the NLTS first adjacent transition, with the exception that there are two bit intervals between the transitions. The amount of shift in this case is [image]. The direction of the shift is determined by the direction of the transitions (earlier if the transitions are opposite, and later if the transitions are in the same direction).

The application calculates this measurement using the following equation:

Where: 	is the playback voltage for a readback channel affected by
NLTS second adjacent transition

V(t) is the playback voltage in the absence of nonlinear effects

T is the bit period

is the amount of shift

and [image] are integers, whose unique values are determined by
the polynomial used to generate the recorded pseudo–noise bit
sequence

The measurement reports the nonlinear effect as a percentage of T; that is, [image].


Other Measurements

The Signal-toNoise Ratio (SNR), Asperity, Overwrite, Resolution, and Baseline Shift measurements perform other specialized functions.

See Also

SNR Measurement

Asperity Measurement

Overwrite Measurement

Resolution Measurement

Baseline Shift Measurement


SNR Measurement

The SNR measurement determines the ratio of the variance of the readback signal to readback noise. The measured noise consists of media noise, crosstalk, electronic noise, and other noise types characteristic to disk drives. Electronic readback noise effects can be mitigated by the averaging operation performed by the SNR measurement.

Signal–to–noise ratio is defined in terms of variances of the signal and noise, and thus is independent of DC offsets of the readback voltage. The SNR measurement algorithm assumes that the acquired signal consists of a periodic signal and independent additive noise. The noise is assumed to be responsible for all the nonperiodic behavior of the acquired waveform. Noise samples are assumed to be independent and identically distributed.

The application calculates this measurement using the following equation:

Where: 	 is the variance of the noise–free periodic signal

 is the variance of the noise

The application performs the measurement according to the following algorithm:

1.	Acquire three or more cycles of the waveform.

2.	The user specifies the number of bits in the data pattern and the duration of the pattern, within a known tolerance.

3.	(This step is not performed if the user specifies a Duration Tolerance of 0%.) Compute the actual cycle time and delay values. SNR guarantees that the real cycle time is determined by the measurement if the initial user estimate for the cycle time is within the specified tolerance (up to 30%) of its real value.

The SNR measurement uses several cycles of the waveform to improve the accuracy of the measurement, averaging over multiple single–waveform cycle SNR values.


Asperity Measurement

The Asperity measurement determines whether the head has hit a flaw in the media surface (a thermal asperity has occurred). When the head hits the surface of the media, a large voltage spike results.

The application performs the measurement according to the following algorithm:

1.	You enter a threshold value to specify what is considered an asperity. the threshold needs to be set to a level greater than TAA.

2.	Begin testing for asperities, checking each peak/trough pair against the specified threshold. If the TAA for a peak/trough pair exceeds the threshold, report an asperity.

3.	Display the results: the sector number where the asperity occurred and the time relative to the start of the acquired data record.


Overwrite Measurement

The Overwrite measurement determines the amount of residual signal remaining from a previous write after new data is written to the same location. The strength of the residual signal depends on the coercivity of the media, write current amplitude, and saturation characteristics of the head.

The application calculates this measurement using the following equation:

Where: 	is the residual RMS amplitude

is the RMS amplitude

The application performs the measurement according to the following algorithm:

1.	Erase the test track.

2.	Write data for one revolution at a low rate f1.

3.	Measure the RMS amplitude (Vo) through a narrow band filter tuned to f1.

4.	Overwrite the track with data at a high frequency f2.

5.	Measure residual RMS amplitude (Vr) at f1 again.

6.	Calculate the results.

7.	Display the results.


Resolution Measurement

The Resolution measurement is a ratio of two TAA measurements: a low–frequency pattern to a high–frequency pattern.

The result is expressed as a percentage. You can use this measurement to infer the raw write density of the disk.

The application calculates this measurement using the following equation:

Where: 	is the low–frequency TAA measurement

is the high–frequency TAA measurement

The application performs the measurement according to the following algorithm:

1.	Erase the test track.

2.	Write data for one revolution at a high frequency [image].

3.	Measure the TAA over the selected range of sectors.

4.	Erase the test track.

5.	Write the track with data at a low frequency [image].

6.	Measure the TAA over the selected range of sectors.

7.	Calculate the ratio of the high–frequency TAA to the low–frequency TAA.

8.	Display the results.


Baseline Shift Measurement

The Baseline Shift measurement is the difference between the baseline of the positive pulse and the baseline of the negative pulse.

The application calculates this measurement using the following equation:

Where: 	v1 is the baseline of the positive pulse

v2 is the baseline of the negative pulse

The application performs the measurement according to the following algorithm:

1.	Measure the time position of a positive peak.

2.	Measure the time position of the following negative peak and the following positive peak.

3.	Use the peak–to–peak value (Vpp) of the Read signal and calculate the difference between the two baselines.

4.	Display the results.


Snapshot Measurements

To see the summary measurements available for TAA, PW50, or NLTS, you can use the snapshot version of these measurements. Display examples of snapshot measurement data for the different measurements.

Snapshots take the following measurements:

•	Amplitude asymmetry

•	Time asymmetry

•	Time peak–to–trough

•	Time trough–to–peak

See Also

Amplitude Asymmetry

Time Asymmetry

Time Peak-to-Trough (Time PT) and Time Trough-to Peak (Time TP)


Snapshot Measurement Examples


Amplitude Asymmetry

The Amplitude Asymmetry measurement uses TAA values to compare the symmetry of the positive and negative pulses. It is available only in the TAA snapshot display.

A zero value for Amplitude Asymmetry indicates that the signal is totally symmetric.  A non-zero value indicates the percent of asymmetry of the signal. The range is from -100% to 100%.

 The application calculates this measurement using the following equation:

Where: 	TAA+ is the mean of the calculated TAA+ measurement for a given sector.
TAA-  is the mean of the calculated TAA- measurement for a given sector

Peak Value is the absolute value of TAA+ or the absolute value
of TAA-


Time Asymmetry

The Time Asymmetry measurement measures the ability of the head and the media combination to process positive and negative transitions identically. The time asymmetry measurement is based on timing between pulse peaks.  It is available only in the PW50 snapshot display.

The application calculates this measurement using the following equation:

Where: 	i indexes negative pulses

N is the number of measured time intervals

is the time from the prior positive pulse to the current pulse

is the time from the current pulse to the next positive pulse

These measurements operate as other measurements in the sense that a range of sectors is defined, and the measurement average and standard deviation calculated. The range of the measurement within each sector is determined by the cursors.


Time Peak-to-Trough (Time PT) and Time Trough-to Peak (Time TP)

The time peak–to–trough (Time PT) is the time from a positive peak to the next negative peak (trough). The time trough–to–peak (Time TP) is the time from a trough to the next positive peak.

The following figure shows the part of the waveform that the application uses to take the measurement.


Introduction to Track Profile Plots

Track Profile plots are reference memory waveforms that contain measurement results from each track sector. The results are distributed over a 500 point record. You can use track profiles to help analyze a measurement in the following ways:

•	Observe sector–to–sector variations in measurements

•	Identify the location of flaws within a track

•	Observe characteristics of measurement variations around a track which may be due to causes such as head height variations or surface media defects

The resulting Track Profile plot represents the value of the measurement as a function of sector number over a range of sectors, which can be specified in the Inputs/Trigger menu. The Trigger Mode must be set to Sector and you have to use the vertical cursors on the oscilloscope for the application  to display the Sector at Cursor readout.

Display an example of a Track Profile plot with readouts.

See Also

Using Track Profiles

About the TrackProfile Reference Memory


Using Track Profiles

To create a Track Profile plot, see creating and viewing track profile plots.

To view ongoing track profile results, set the Sequence Mode to Free Run. When the Track Profile plot reaches its 500–point capacity, the application continues to acquire data and the plot scrolls across the screen as new points are added and old points are deleted.  Display an example of a Track Profile plot from a TAA measurement.


About the TrackProfile Reference Memory

At the beginning of the measurement, the reference memory is filled with null values. At the end of each sector measurement, the value for that measurement is stored in the reference memory and a display cycle is activated. This causes the reference memory waveform to sweep across the screen as the measurement progresses around the track. You then have a clear indication of the progress of the entire measurement over the specified range of sectors.

Values are stored in the reference memory as one point per measurement result, up to a maximum of 500 points. If more than 500 points/measurements are taken, the oldest results are discarded. Any unused points at the end of the reference memory record are set to null values.


About the GPIB Program Example

This section contains an example of a GPIB program that can execute the TDSDDM2 application. The oscilloscope hard disk and optional applications compact disc both contain this program in the ddm2ctrl.c file.  The file resides on the hard drive in the C:\Program Files\TekApplications\tdsddm2 directory.

This example shows how a GPIB program might execute the application to do the following tasks:

•	Start the application

•	Select a measurement

•	Select an input

•	Define a waveform

•	Enable the logger

•	Take a measurement

•	Check for an error

•	Exit the application

See Also

GPIB Guidelines

GPIB Program Example

Introduction to GPIB Command Syntax


Guidelines to GPIB Programming

Your GPIB program should comply with the following guidelines:

•	The application startup must complete before sending additional GPIB commands to the application (see example).

•	The measurements cycle must complete before data is queried (see example).

•	The error variable should be checked to ensure that an error has not occurred because of a measurement command problem.


GPIB Program Example

/* C Program Example: TDSDDM2 GPIB control	*/
/* ====================================================================
 * This sample program is for Tektronix Java application TDSDDM2 --
 * Disk Drive Measurements
 *
 * Note1: In order to build the .exe correctly, copy gpib-32.obj from
 * "C:\Program Files\National Instruments\GPIB\NI488\LangInt\C\" or
 * "C:\Program Files\GPIB-NT\LangInt\C\ to
 * the workspace.
 *
 */

 #include <string.h>
 #include <stdio.h>
 #include <sys/timeb.h>
 #include <windows.h>
 #include "C:\GPIB-NT\LangInt\C\decl-32.h"

 int start_application(/* in */ int scope);
 int do_single_test(/* in */ int scope);

 void main (void)
 {
char read_buffer	[100] = "";
char write_buffer [100] = "";
int	scope;
int	status;

/*
 * Open session for IBIC
 */
scope = ibfind ("DEV2");
status = ibpad (scope, 1);
status = ibtmo (scope, T10s);

status = ibwrt (scope, write_buffer, strlen (write_buffer));

/*
 * Start Application
 */
if (start_application(scope)){
printf ("Application is started up!\n");

/*
 * Turn on a measurement (TAA)
 */
sprintf (write_buffer, "%s", "Variable:value \"measurement\",\"TAA\"");
status = ibwrt (scope, write_buffer, strlen (write_buffer));

/*
 * Select Source Type -- REF
 */
sprintf (write_buffer, "%s", "Variable:value \"readSignal\", \"Ref1\"");
status = ibwrt (scope, write_buffer, strlen (write_buffer));

/*
 * Recall Waveform to Ref
 */
sprintf (write_buffer, "%s", "recall:waveform
 \"c:\\TekApplications\\tdsddm2\\waveforms\\diskdrive.wfm\", REF1");

status = ibwrt (scope, write_buffer, strlen (write_buffer));

/*
 * Display Ref1
 */
sprintf (write_buffer, "%s", "select:ref1 on");
status = ibwrt (scope, write_buffer, strlen (write_buffer));

/*
 * Turn on Log Statistics for TAA measurement
 */
sprintf (write_buffer, "%s", "Variable:value \"TAAloggerState\",\"On\"");
status = ibwrt (scope, write_buffer, strlen (write_buffer));
/*A Timer is needed after setting the loggerState on*/
Sleep(2000);

/*
 * Do a single test
 */

if (do_single_test(scope)){

/*
 * Set Measurement for which you want to query test result -- TAA
 */
sprintf (write_buffer, "%s", "Variable:value \"resultFor\", \"TAA\"");
status = ibwrt (scope, write_buffer, strlen (write_buffer));

/*A Timer is needed after setting the measurement to be queried*/
Sleep(500);
/*
 * Query mean result
 */
sprintf (write_buffer, "%s", "Variable:value? \"mean\"");
status = ibwrt (scope, write_buffer, strlen (write_buffer));
status = ibrd (scope, read_buffer, sizeof (read_buffer));

if (ibcnt != 3) {	/* It’s not an empty string */
read_buffer [ibcnt] = 0;	/* Get rid of extra characters */
printf ("Mean TAA = ");
printf ("%s", read_buffer);
}
}
else
printf ("*** Fail to query result ***\n");

}
else{
printf ("*** Fail to start Application ***\n");
return;
}

/*
 * Display Off for Ref1 before exiting
 */
sprintf (write_buffer, "%s", "select:ref1 off");
status = ibwrt (scope, write_buffer, strlen (write_buffer));

/*
 * Exit application
 */
printf ("Exit application!\n");
sprintf (write_buffer, "%s", "Variable:value \"application\",\"exit\"");
status = ibwrt (scope, write_buffer, strlen (write_buffer));

/*
 * Program Ending
 */
printf ("Program Terminating Normally\n\n");

return;

 }

/*--------------------------------------------------------------------------
 * Function: start_application
 * Argument: scope
 * Return: 1 if success, 0 otherwise
 *
 * This function starts the application and comfirms the completion of startup
 */
 int start_application(/* in */ int scope)
 {
char read_buffer	[100];
char write_buffer [100];
char app_name[30] = "\"tdsddm2\"\n";
int	status;
int	timer = 0;
int	i = 0;

/*
 * Has application already been started?
 */
sprintf (write_buffer, "%s", "Variable:value? \"application\"");
status = ibwrt (scope, write_buffer, strlen (write_buffer));
status = ibrd (scope, read_buffer, sizeof (read_buffer));
read_buffer [ibcnt] = 0;	/* Get rid of extra characters */

if (strcmp(app_name, read_buffer) == 0){
return 1;	/* Application is running, don’t need to do anything */
}

/*
 * If application is not started up, start it and wait for application to completely
 * start up
 */

sprintf (write_buffer, "%s", "Application:activate \"Disk Drive Measurements V2\"");
status = ibwrt (scope, write_buffer, strlen (write_buffer));
printf ("Starting application, please wait...\n");
while (strcmp(app_name, read_buffer) != 0){
timer = timer + 2;
if (timer > 45) {	/* The application normally take 24 seconds to start up */
printf ("***Application start up time out***\n");
return 0;	/* Something is wrong if application does not start up in 30s */

}
sprintf (write_buffer, "%s", "Variable:value? \"application\"");
status = ibwrt (scope, write_buffer, strlen (write_buffer));
status = ibrd (scope, read_buffer, sizeof (read_buffer));
read_buffer [ibcnt] = 0;/* Get rid of extra characters */
Sleep(2000);

}
/* Application start up! */

return 1;
 }

/*--------------------------------------------------------------------------
 * Function: do_single_test
 * Argument: scope
 * Return: 1 if success, 0 otherwise
 *
 * This function does a single measurement
 */
 int do_single_test(/* in */ int scope)
 {
char read_buffer	[100];
char write_buffer [100];
char state[10]	= "\"Ready\"\n";
int	status;
int	timer = 0;
int	i = 0;

/*
 * Start measurement
 */
printf ("Do a single test...\n");
sprintf (write_buffer, "%s", "Variable:value \"sequencerState\",\"Sequencing\"");
status = ibwrt (scope, write_buffer, strlen (write_buffer));

do{
timer = timer + 2;
if (timer > 60) {	/* Assuming a single test takes less than 60 seconds */
printf ("***Test time out***\n");
return 0;	/* Something is wrong if sequencerState does not come back
* to Ready */
}
sprintf (write_buffer, "%s", "Variable:value? \"sequencerState\"");
status = ibwrt (scope, write_buffer, strlen (write_buffer));
status = ibrd (scope, read_buffer, sizeof (read_buffer));
read_buffer [ibcnt] = 0;/* Get rid of extra characters */
Sleep(2000);
}while (strcmp(state, read_buffer) != 0);

return 1;
 }


Introduction to GPIB Command Syntax

You can use the GPIB command syntax in your GPIB program to do the following tasks:

•	Start the TDSDDM2 application

•	Recognize an active application with GPIB protocol

•	Program and read application setup parameters

•	Sequence measurements

•	Read measurement results

To use GPIB commands with your oscilloscope, you can use the following reference materials:

•	The tdsddm2ctrl.c file on the oscilloscope hard drive (located in the C:\Program Files\TekApplications\tdsddm2 directory) and on the optional applications compact disc contains an example of a GPIB program that can execute the application

•	The GPIB Program Example section for guidelines to use while designing a GPIB program

•	The Parameters Reference section for incremental units and default values of TDSDDM2 parameters

•	The programmer information in the online help of your oscilloscope

You should be familiar with the following terms when using GPIB command syntax:

Description: Gives the function of the command, conditions of its use, and its interactions with other commands.

Syntax: Gives the valid select and query command forms. The required arguments are listed in their proper order.

For example, in the syntax definition:

PATH= <Ad><Ars>

the arguments <Ad> and <Ars> are required in the order indicated

Arguments: The arguments to a command are defined along with their range of values.

Returns: Defines the data returned in response to a command query.

See Also

Starting the Application using GPIB

Variable: Value TDS Command


Starting the Application Using GPIB

To start the TDSDDM2 application, you must send the oscilloscope the following GPIB command:

application:activate "Disk Drive Measurements 2"

See Also

Variable: Value TDS Command

Variable:Value TDS Command Arguments and Queries


Variable: Value TDS Command

VARIABLE:VALUE TDS COMMAND accepts string arguments for a control or data variable and a value to which to set the argument.

Syntax:

VARIABLE:VALUE “<variable name>”,“<variable value>”

The arguments <variable name> and <variable value> are required in the order indicated.

VARIABLE:VALUE? “<variable name>” for query

CAUTION.  Commands are case and space sensitive.  Your program will not operate correctly if you do not follow the capitalization and spacing precisely.

See Also

Variable: Value TDS Command Arguments and Queries

Required GPIB Command Sequence

Measurement Results Queries

Results Returned by Measurements


Variable: Value TDS Command Arguments and Queries

See Also

Required GPIB Command Sequence


Required GPIB Command Sequence

Before you can request result queries, be sure that your program contains the following sequence of commands:

measurement

sequenceMode

sequenceState

resultFor

After this sequence, you can query the results.  If you have a subsequent sequencing for the same measurement, you must issue another resultFor.

You need to use the VARIABLE:VALUE? form to enter measurement results queries in your GPIB program.  See the topic, Results Returned by Measurements, for the measurement selected in the resultFor variable.


Measurement Results Queries

See Also

Results Returned by Measurements


Results Returned by Measurements


Copyright and Version
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by Tektronix or its suppliers and are protected by United States copyright laws and

international treaty provisions.

Tektronix products are covered by U.S. and foreign patents, issued and pending. Information

in this publication supercedes that in all previously published material. Specifications

and price change privileges reserved.

TEKTRONIX and TEK are registered trademarks of Tektronix, Inc.

TDSDDM2 Communications Pulse Measurements Online Help, 076-0064-00, Version 3.0.0

Contacting Tektronix

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Beaverton, OR 97077 USA

For product information, sales, service, and technical support:

•	In North America, call 1-800-833-9200

•	Worldwide, visit www.tektronix.com to find contacts in your area