New Lease of Life - Tester Upgrades
We are used to throwing away printers and PCs after only a few years of use. Can we afford to do the same with aging test equipment?
Do we take the same care of our aged test equipment as we do for human beings? These days people spend a lot of money to avoide the symptoms of getting older. Vitamin pills, wrinkle creams, and health studios, just to name a few. But what if our equipment is aging? Do we just throw it away if it doesn't meet today's standards or requirements? Salland Engineering has developed some new products that can be used to bring existing test-systems back on track.
Salland's goal was to develop a tester-processor replacement, which could run existing test-application programs, add functionality to the tester such as network capabilities, and give a quick return of investment. The benefits for the user should be test-time reduction and lifetime expansion.
"The approach we took was to take a commercially available fast PC and use this to replace the existing tester processor. We have direct benefits, such as networking possibilities, large hard disk capacity, large memory, windows environment, and ease of use," says Paul van Ulsen, managing director of Salland Engineering in The Netherlands.
"Before we had the tester processor replacements, we had to overcome the following problems; How to connect? What happens with the existing test software? How fast can we get it to run?"
The solution to this was writing an emulation program under Windows NT 4.0 for the existing tester processor. The result is that all instructions are handled exactly the same way as on the original processor. By using a dual Pentium system, one Pentium processor can run the emulator while the other performs all other actions.
All in the emulation
The test program is in the tester memory. This is a list of instructions that must be carried out in a certain sequence. The instructions are written in a specific format for the tester processor. To start with, an allocation table for a second memory just as big as the tester memory, but with a difference. The tester memory is pointing to the address of the jump table memory. The instruction has become an address. At this particular address, there is a pointer to a code-table, written in Pentium X86 instructions, which will carry out the exact same function as the original instruction. Because look-up tables are used, other X86 code compatible processors can be used, such as those made by AMD.
Emulation is never as fast as a dedicated processor, and it is possible that one tester instruction will require up to 20 pentium instructions to have the same result. The speed difference will easily compensate for this, in fact, speed is even gained. By having the tester memory on the PC together with the emulation memory, it is possible to gain maximum speed. The emulation program consists of approximately 500 Pentium instruction code tables. All existing test software can still be used.
The next generation
The older generation of test systems are mainly equipped with even older style processors. The clock frequency is up to 20 MHz, but can also be as low as 4 MHz. Today a dual Pentium is available on the market at clock frequencies of just about 1 GHz. The nice thing is that when new developments create faster PC's, they can easily be installed. The cost of a PC compared to that of a tester is minimal.
To replace the existing tester processor, the customer has to pull the memory and processor board out of the old system and replace the empty slot with a back plane board developed by Salland Engineering. This card provides the connections between the tester and the new PC card.
The connection between the tester and the PC is made by IEA-485 differential bus traceivers to avoid interference and noise. On the PC side, PCI slots are used. The plug-in cards are quipped with Field Programmable Gate Array's. All local storage media in the tester is replaced as well. The size of the accessible memory is also expanded. Some older testers still use tape drives to load programs. With a PC storage medium, the process of uploading and downloading programs is much faster and easier. There is a real-time yield monitor in the user interface, which can report the test results in a graph as well as by bin (color coded).
Test system users do not have serious conversion problems as long as the new tester has the same style processor. Newer testers also have new style processors that provide todays required features. Problems will arise when the customer wants to run all of the existing test programs. Conversion programs will not be able to generate a program that will run without debugging or the need to be rewritten. Rewriting is expensive and resources are hard to find. With a full tester processor emulation, all existing software can still be used without modification. In a few cases, such as analog applications, the program may require some extra wait loops. In practice, Salland has achieved test-time reduction of up to 60% (on average 15-30%). If the emulator is installed on a regular PC, it can also be used as an offline debug tool.
Salland Engineering's processor replacements bring easy migration and give older test equipment a new life. Salland provides the vitamins and health care to keep the aged testers fit. The need for older testers may be higher than you think due to the foreseen tester shortage in the near future. It is better to have an old and improved tester on your test floor than running out of capacity.
Tester processor replacements are available for Advantest, Sentry, Teradyne, MCT, LTX and Ando.