built in self test

Discussion in 'General Electronics Chat' started by vead, Jun 16, 2014.

  1. vead

    Thread Starter Active Member

    Nov 24, 2011
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    vlsi circuit also contain additional test circuit , circuit that allow to test their own operation by itself


    built in self test process that allow to test their own operation by itself

    I don't understand how does circuit allow to test their own operation ?

    someone can give example for basic understanding ?
     
  2. Brownout

    Well-Known Member

    Jan 10, 2012
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    Memory all 1's and all 0's self test.
     
  3. #12

    Expert

    Nov 30, 2010
    16,248
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    There are (at least) a thousand ways to design in a self-test ability. Even a fuse could be considered to be a self test. Each circuit is designed for what the designer wants to protect.

    Here is a circuit I designed to stop an air conditioner for any of 4 failure modes. As it turns out, the sensors must all be, "good" or the machine won't start. This is primitive form of self testing.
     
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  4. vead

    Thread Starter Active Member

    Nov 24, 2011
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    look at this way
    just for example , we made micro controller circuit . If decoder circuit in microcontroller is faulty , how does circuit detect fault by self checking that decoder is faulty
     
  5. Brownout

    Well-Known Member

    Jan 10, 2012
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    What decoder circuit? BIST doesn't test 100% of a design. Typically, it tests the interfaces and memory. It's rather like the self test a PC runs on startup.
     
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  6. vead

    Thread Starter Active Member

    Nov 24, 2011
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    It means built in self test is used to test memory and connection in circuit

    what is memory testing process ?
     
  7. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Often this is done by connecting all or part of the decoder outputs back into the microcontroller. The uC sends a test data pattern to the decoder, and monitors the decoder output to make sure they are correct. Analog modems did the same thing with tones. The modem could close a relay to connect the analog output back to its own input (called a loopback test), to make sure it could decode itself correctly.

    There are many different ways to implement a self test capability, depending on the king of system and how deeply you want to go into testing. Also, sometimes self tests run only on power up Power On Self Test - POST) and sometimes they run continuously in the background wile the system is operational.

    ak
     
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  8. vead

    Thread Starter Active Member

    Nov 24, 2011
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    what is difference between memory BIST and LOGIC BIST ?

    I think memory BIST is used for embedded memory

    IF built in self test is used to test memory and connection in circuit

    why do we used logic BIST ?
     
  9. IC-Man

    New Member

    Jan 3, 2012
    26
    4
    Build in selftest in mirocontroller systems can be done in software to test:

    - memory, e.g. by walking pattern or checksums
    - ALU - by adding know pattern to create all one and all zero
    - I/O - by writing and ready back the outputs value

    Specifically the I/O port error monitoring needs special structure to do a selftest, like decribed here: http://www.ichaus.de/upload/pdf/IO-Error Monitoring JX.pdf .

    Another option is to use JTAG to get access to the specific test points inside the VLSI circuits.
     
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