Integrating Femto 2000 Test Code to a Teradyne Integra Test Program

Introduction

The purpose of this applications note is to explain how to utilize the Femto 2000 Time Interval Analyzer to make direct, precision time measurements on the Teradyne Integra (J750) platform.

Prerequisites:

• Training on the Teradyne J750 test platform.
• Applications training on the Femto 2000 TIA.

The J750 test platform is a Windows NT system that uses Teradyne's IG-XL software for programming. The IG-XL software is similar to Microsoft Excel through its file structure and it also allows the user to add special functions to the test program through Microsoft's Visual Basic programming language.

System Hardware Configuration:

There are two levels of system hardware configuration, the Femto 2000 and the J750. Femto 2000 Hardware Configuration The Femto 2000 can have up to a maximum of four sites with eight measurement channels.

Each site has two independent measurement channels and both channels can be configured as single-ended or differential inputs. In addition, the Femto 2000 comes with high bandwidth coaxial cables called the GT_QuikConnect. The GT_QuikConnect has two sections, the cables that mount to the Femto 2000 and the headers that mount to the Device Interface Board (DIB). Each header has eight coaxial cables. A minimum of three cable/header sets are needed to interface to the DIB, two signal connectors and one arming connector. (See figure 1 and figure 2).

NOTE: Please consult GuideTech for details on DIB design considerations.

J750 Hardware Configuration The J750 can be configured up to 1024 pins, a number of utility pins, and power and ground supplies. The Femto 2000 does not use up resources of the J750 in order to function. You need to lay out the DIB to the desired tester configuration.

NOTE: The J750 must have a GPIB card to communicate with the Femto 2000.

System Software Configuration Femto 2000 Software Configuration When the Femto 2000 is integrated with other instruments, such as automatic test equipment (ATE), it requires the user to install a platform-specific software driver. This software driver is made from five files: · gt_drvr.c · gt_drvr.h · gt_host.c · gt_host.h · A c dynamic-link-library file - f2000.dll These files have all of the commands to program the Femto 2000 through GPIB. The software driver also has a Visual Basic interface. The Visual Basic interface is made up of: · A Visual Basic driver - GT_DRVR.bas · A Visual Basic dynamic-link-library - F2000VB.dll. The F2000VB.dll provides the necessary hooks to the c-file to program the Femto 2000 using Visual Basic as the programming language. When compiling the Femto 2000 test code into the J750 test program, the Visual Basic interface (F2000VB.dll) must be in the same directory as the source (name.xls) J750 test program. How the Femto 2000 test code is added to the J750 source program will be discussed later.

J750 Software Configuration

The Femto 2000 test code can be incorporated into any revision of the IG-XL software. Therefore, no special considerations are needed to incorporate the Femto 2000 test code. GPIB Configuration The GPIB configuration needs to be set from the front panel of the Femto 2000 to the address that the user specifies. The user can specify addresses ranging from 1 to 30 (typical is between 1 and 7). The user can now specify this address in the test program to communicate with the Femto 2000. Adding the Femto 2000 Test Modules To add the Femto 2000 test code modules to the J750 test program source code, you must go to the menu bar in IG-XL and select Tools/Macro/Visual Basic Editor. (See figure 3). That will launch the Visual Basic editor where IG-XL test code can be modified and the Femto test can be added. Figure 3 - To Launch Visual Basic Editor The Femto test code can be added to the J750 test program as a Visual Basic module. To add a module, from the menu bar, go to Insert/Module. A blank module will be inserted in to the test program. (See figure 4). To avoid compilation errors, always type the words Option Explicit.

The use of Option Explicit helps to avoid incorrectly typing the name of an existing variable or to avoid confusion in code where the scope of the variable is not clear. (See figure 4). If used, the Option Explicit statement must appear in a module before any procedures. When Option Explicit appears in a module, all variables must be explicitly declared using the Dim, Private, Public, ReDim, or Static statements. If you attempt to use an undeclared variable name, an error occurs at compile time. If the Option Explicit statement is NOT used, all undeclared variables are of Variant type unless the default type is otherwise specified with a Deftype statement. Figure 4 - To Add a Visual Basic Module When the module gets added to the test program, its default name is Module. This is a meaningless name to you and needs to be renamed. A module can be renamed from the menu bar by selecting view/properties window. The properties window indicates the current module you are in. You can enter a meaningful name by clicking on the name, deleting it, and typing in a new name that indicates the type of test being performed, i.e., GT_Frequency_Test. (See figure 5).

Once the module name has been modified, the user can enter the necessary Femto 2000 test code for the desired measurement type. The J750 has specific functions called interpose functions. These functions enable you to execute test code when a specific event has occurred in the tester hardware. The list of pre-defined interpose functions are as follows: · OnTesterInitialized() - Immediately at the conclusion of the initialization process · OnProgramLoaded() - Immediately at the conclusion of the load process · OnProgramValidated() - Immediately at the conclusion of the validate process · OnTDRCalibrated() - Immediately at the conclusion of the TDR calibration process · OnProgramStarted() - Immediately after "pre-job reset" when the test program starts · OnProgramEnded() - Immediately prior to "post-job reset" when the test program completes.

To begin programming, you must first initialize the Femto 2000. The most appropriate place to enable the initializations sequence of the Femto 2000 is in the OnTesterInitialized() interpose function. When the tester is initialized, it will execute any test code that is inside that particular function. Adding the Femto initialization code to this function will not impact test times. (See figure 6).

Normally, you would execute a command checking for errors when a read or measure function has been called. Because IG-XL does not support all of the functions of Visual Basic, a special function to check for errors was developed. This is an interim development until further integration between IG-XL and Femto 2000 software has been completed. The GtCheckErrors() function can be inserted in the program and used in place of the original gt_check_errors() function. (See code example 1).

Example 1

Public Function GtCheckErrors() As Long Dim last_err As ERROR_DATA Call gt_get_last_err(last_err) If last_err.code <> 0 Then ' MsgBox last_err.msg, vbCritical, "Error" TheExec.Datalog.WriteComment ("Femto 2000 Error[" & Right$("0000000" & Hex$(last_err.code), 8) & "]: " & last_err.msg) GtCheckErrors = GT_FAILURE End If GtCheckErrors = GT_SUCCESS End Function

NOTE: Because IG-XL does not have an OnProgramUnloaded() interpose function; the Femto 2000 command to close GPIB communications (gt_close) does not get utilized. The Femto's initialization sequence will reset GPIB communications.

Next, you can add specific test code for the Femto 2000 to make precise, high-speed time measurements. For simplicity, three commands can be used to operate the Femto 2000: gt_setup_[measurement](), gt_start_measurement(), and gt_wait_and_read() the results. All other commands and programming are essentially for error checking, debug, data logging, and pattern execution. (See figure 7).

The data logging function of the J750 is handled by TheExec.Datalog.WriteComment() command. (See code example 2).

Code Example 2 TheExec.Datalog.WriteComment ("CH_" & chan_name & " mean = " & Str(meas(index).mean / 1000000#) & " MHz")

Modifying the J750-Integra Test Program

Once the modules have been created to perform specific measurements on the Femto 2000, you need to call the modules from inside the J750 test program. Calling the modules from within the test program involves inserting the module names at various points in the test program. First, the test program needs to be modified. The test program needs a test instance that identifies the test to be performed by the Femto 2000. (See figure 8).

Next, all of the AC and DC parameters as well as a new channel map need to be completed on the IG-XL software to reflect the DIB and Femto 2000 specifications.

NOTE: The Teradyne J750 training course will instruct the user how to do this. Once the additions have been made to the test instance sheet, you need to insert the functions into the Functional Instance Editor.

This allows you the freedom to call the functions at various points in the program execution. (See figure 9). You add the function names used for the Femto 2000 and place them in the Interpose Function tab of the Functional Instance Editor. (See figure 9-below).

As indicated before, the levels and timing also need to be added to the Functional Instance Editor. (See figure 10-below).

Test Pattern Generation

The device under test (DUT) must be pre-conditioned to generate continuous signals while the Femto 2000 is making measurements. This is usually accomplished by modifying an existing device pattern to enter an endless loop during the pattern. To use this method, the Pattern Editor tool is used to insert a loop and halt into an existing pattern. A pattern label is then created for the new loop pattern. In addition, where the user has the specific Femto test code, the IG-XL command Call thehdw.Digital.Patgen.Continue(0, 1), will start the pattern looping, make the measurements, and then stop the sequencer.

This command must be inserted before the measurement results are read from the Femto. In addition, a trigger channel may need to be inserted into the test patterns to allow for external ARMING of the Femto 2000. Error Recovery The test system may occasionally hang up during test development, especially if the endless loop pattern is not terminated correctly within the test program. Recovery from this type of error is similar to an error recovery within the Windows operating system. This can be accomplished by pressing Ctrl-Alt-Del. The Windows task manager pop-up indicates which applications are running. Pressing the end-task button can stop the portion of the IG-XL application that is not responding.