| ??? 10/06/10 16:48 Read: times Msg Score: +1 +1 Informative |
#178954 - And the type covered again and again Responding to: ???'s previous message |
Why do you ask about how to use an XOR discriminator for measuring signal propagation if you want to know how to differentiate between different models?
On your specific request, I did show an example of diffierentiating between '161 '163 and '365. You forgot your question? Or forgot to check the answer? I did mention it was bad examples for demonstrating a decision tree, since the '161 and '163 are so similar that you want to separate them as last step - using simpler steps with far better pruning abilities at the top of the tree. But all the time, you post stupid questions like: But how do you use XOR for finding if a pin is input or output or a '161 or '365. Answer - I don't. Multiple times repeated. I would do it the traditional way by setting signals to known states and reading back the result. Repeat, rinse through decision tree until having zero, one or multiple chips and no more discriminating rules to test. Not a single XOR involved, unless the subject under test happens to be a 74x86 or maybe a 4070. No, Richard. I am not going to build the test vectors for two hundred chips and post a decision tree here just because you ask random questions. Jeckson Ben will have to do that himself. Notice that it isn't he who are asking the questions. Richard said:
Your cartoon shows a single signal headed for a single XOR to a single LPF, and a single ADC. How does that apply to determining which of the many 16-pin IC's "this one" would be? Already covered a about a billion times in this thread. It doesn't. The XOR discriminator isn't involved for separating '00 from '04 from '86 from '161 from '193. It is an optional extra to measure propagation delay after test vectors have figured out that the logic table matches a '86. Will we see you repeat your question in more posts? Yes probably. You have asked it at least 5 times already, but still not getting it. Richard said:
The typical hobbyist, as I mentioned before, is interested in knowing (a) what this IC is, and (b) whether it is still working properly, because it once was. And how does that deviate from this text, which you obviously did not remember to read: Per said:
The XOR thing has only (O.N.L.Y.) meaning after the chip and chip pins have been identified. And only as an optional step to measure propagation delays. http://www.8052.com/forum/read/178934 Per said:
Someone who wants to make a really cool tester could add a high-frequency oscillator allowing a square wave to be sent through a gate and mixing it using an XOR gate with undelayed square wave data. Combining the two signals and low-pass-filter the result would give an analog value that depends on gate delay times allowing a tester to make guesses between 7400, 74LS00, 74ALS00, 74HC00. http://www.8052.com/forum/read/178792 How does it feel, Richard, to constantly ask the same thing, despite constantly being shown quotes from earlier posts already answering your question hours or days before you asked it? And still you come back and repeat those same questions again and again. Is it that you don't remember you have asked them? Or that you have already received answer to them? Or is the thread a bit too high-tech for you? And since you can't remember more than one thing at a time, our posts always results in: - you ask about how to measure propagation delay - I give example - you post: but what use if you don't know what chip. - you ask: how do you know what chip - I give example - you post: but what use if you can't measure the propagation delay. - you ask: but how do you use an xor to figure out if a pin is tristated - I answer: I don't. I walk test patterns to find out if a pin is tristaed or not - you: but what has that with XOR to do - or but how do you get the propagation delay So when you ask for A, you don't expect the answer to A but the answer to B. And when you ask for B, you dont' want an asnwer to B but an answer to A. You have entered a feedback loop with amplification > 1. |
