DFT

"The Lord your God is testing you to find out whether you love him with all your heart and with all your soul."
-Deuteronomy 13:3b
     The past two weeks have been absolutely insane for me at work. I've been tasked with many assignments and I often feel out of my depth. Interestingly, I've been thinking about writing this post for a while, but it turns out that this might be the perfect time because it applies so well to my current situation. I hope you are encouraged as you read through this blog entry.
     If you happen to be an engineer, you might know that the acronym "DFT" stands for "Discrete Fourier Transform". You might also know that discrete Fourier transforms are extremely complex and boring. Today I don't want to talk about that DFT. I want to talk about DFT in the context of test engineering. If you are a test engineer, you probably know that "DFT" stands for "design for test".
     What DFT refers to is the capability of a device or system to be tested. The testing of products is extremely important in the semiconductor industry, as it is in many industries. When a device is being designed, the designers must consider how the device will be tested. This is where DFT comes in. Design engineers and test engineers work together to create functions in the device that allow it to be thoroughly tested. Design for test functions are only for the testing of the device, and are not used for the actual operation of the device.
     You may wonder why engineers go through the trouble of adding extra capabilities in the device that will not be used in the normal operation of the device. DFT capabilities are added to a device because certain failures cannot be detected without these functions. One of the major DFT functions is the ability to test smaller blocks of the device. For example, the normal usage of a battery charger may use a smaller circuit that feeds into a bigger circuit in the device. A DFT function would be the ability to test the smaller circuit independently of the bigger circuit.
     The most important question to ask is why engineers bother testing devices at all. The answer is quite obvious, even to non-engineers. Testing verifies that the product works as it is intended. If a device is never tested, it is impossible to know whether that device does what it was made to do. What good is a product that cannot do what is advertised?
     I believe that this idea of DFT applies to us as human beings. If you read through the Bible, you will hear many stories of God testing people that He chooses. One great example is Abraham. God asked Abraham to kill his long awaited son Isaac. God didn't ask Abraham to do this because He is a cruel God; He wanted to confirm that Abraham's faith was real. Abraham's test ensured that he was a faithful follower of God.
     Another aspect of DFT is that it allows a device to be changed. When a semiconductor device is developed, the process is not accurate enough to guarantee high repeatability. To compensate for the lack of repeatability, engineers design something called "trims". Trims are circuits that change a certain function of the device. For example, a trim may be used to change the resistance of a battery charger so that the desired resistance can be achieved.
     We too are changed through testing. Tests don't only verify our faith- they can change our faith. God designed us in such a way that sometimes the only way we can be changed is through testing. I have heard countless testimonies of people who were completely changed because of the tests in their life. In fact, I find it rare to hear testimonies where someone is not tested. Everyone's tests are different, but we will each face them. God is using these tests for our good.
     After reading up to this point, it might seem that the idea that we were "designed for test" is quite depressing. Why would God design us just to be tested? I don't believe this is the case. DFT has an alternative meaning, which I found a great liking to: "design for testability". With this new definition, it's clear that DFT functions are intended to make sure the device is able to be tested. Similarly, God didn't design us to be tested; He designed us to be able to be tested. God's purpose for our lives is not to test us, but testing is a part of our purpose. Take heart in knowing that we were designed to be able to be tested. The only question is: will you fail or pass?
-Smart