This section describes the use of HP VEE Test for physical testing of ICs. HP VEE (Visual Programming Environment) is a graphical programming language. A program can be written by using a variety of graphical objects and connecting them into a desired program flow. Graphical objects perform tasks such as input and output, plot graphs, arithmetic, and perform I/O to test equipment such as the D20 hardware and the CMC Test Head. A program may have more than one thread of execution that can be controlled by button objects. A thread can be viewed as a function if only one thread is executing at any given time.
HP VEE is used to create programs to test ICs because it is simple to use and both the CMC test head and the D20 hardware can be easily controlled via "Direct I/O" objects. These objects allow the programmer to enter a sequence of SCPI commands that will be sent to the hardware during the execution of the program. The HP VEE programming software is installed on the HP 700i workstation. To start it, enter veetest at the UNIX prompt.
A VEE program for physical testing consists of four different functions:
By separating the test into four parts makes the programming much simpler. This procedure is slightly different from the approach that CMC uses in its tutorials. The procedure that will be described on this page and in the next section is optimized for testing the same chip in quantity whereas the CMC procedure is good for testing a given chip only once. The reader may choose the appropriate method for his or her needs.
Power on self-test sends commands to the CMC Test Head to set the voltage and current limits. The voltage is increased slowly to the desired value and the current is monitored during the power-up process. If the device under test is faulty, then it may draw more current than the current limit and the power-up process will be halted to prevent any further damage to the DUT. Otherwise, the DUT will be ready for testing. When debugging with the HP Test Development Software, power on self-test must be performed first so that there is power to the DUT.
Test head initialization turns on all the relays so that the timing and pattern pods are connected to the outer wiring array (OWA) pins. Like power on self-test, this step must be completed before tests can be run from the HP Test Development Software.
Load test file uses a HP 75000 Model D20 I/O object to load the exported text file (.ASC file) from the HP Test Development Software into the tester. As described in the last section, the .ASC file consists of a series of SCPI commands to load test vectors and timing information into the memory of the D20 hardware.
Finally, run test uses a direct I/O object of the D20 hardware to send the appropriate SCPI commands to the D20 to start the physical test. After the test has completed, the result is read and any errors will be output to the screen. If an error occurs, then the HP Test Development Software can be used to debug and pinpoint which vector caused the error. As mentioned above, this testing procedure is different from CMC's approach. The functional test program in CMC's digital tutorial loads the SCPI commands and records the responses in a file every time the test is run. This is very slow if there are many test vectors. There is no need to load the SCPI commands into the tester every time if the same test is to be performed over and over. Moreover, it is much easier to locate errors in the HP Test Development Software than using the results written to a text file.
This section gives an overview of how HP VEE can be used to perform physical testing of ICs. The next two sections provide the source of the HP VEE test programs that the reader can follow and create test programs on his or her own.
