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TMS320F28335: inteference test for 28335

Strong ZHANG
Expert 4410 points
Part Number: TMS320F28335

The customer did the experiment to test signal inteference for the MCU  in lab, when they inject 3.3 Volt pulse on the SCI pin of 28335 directly, all the application ISR are disable and only the main function can run. It may induce over-current on the pin of SCI, but it did not destroy the pin, and they want to know why injecting voltage pulse will affect the interrupt, what is the principle?

  • 0
    TI__Guru* 95315 points

    Strong,

    Sorry, but I am unable to understand your question. Please clarify what you mean by "they want to know why injecting voltage pulse will affect the interrupt". 

  • 0 in reply to Hareesh Janakiraman
    TI__Expert 4410 points
    Customer connected the SCI pins of MCU to an external voltage source which generate 100 KHz voltage pulse， and found that in the software all ISR fail to run，but the main function still can run，they want to know why this happen and what make the ISR stop running.
  • 0 in reply to Strong ZHANG
    TI__Guru* 95315 points
    1. Is the experiment repeatable? Meaning, do you see exactly the same result everytime?
    2. Is the result any different if you use a different pin? i.e. instead of using the SCI pin, if you use the PWM pin or a CAN pin, is the result any different?
    3. You mentioned no interrupts are working in the system. Do you have the debugger connected? If so, are you able to examine the value of INTM bit?

     

  • 0 in reply to Hareesh Janakiraman
    TI__Expert 4410 points
    Thanks Hareesh.
    1.yes ，it is repeatable，and the result is the same.
    2.Testing same other pin does not have this problem.
    3.The debugger still connected,the value of INTM was changed, which diable all the interrupts. this test may lead to over-current on the pin，but it didnot destroy the pin，instead it has effect on the interrupts, which is strange.
  • 0 in reply to Strong ZHANG
    TI__Guru* 95315 points

    So, here is what we know:

     

    Customer injects a 0-3.3v , 100 KHz pulse on the SCI pin. This sets the INTM bit, disabling interrupts globally. The outcome is repeatable. Other pins do not exhibit this issue. Is this correct?

     

    Questions:

    1. Is it SCITXD or SCIRXD? Can you provide the exact pin number?
    2. What other pins were tried?
    3. In your first post, you refer to a "overcurrent situation". How does this result in a overcurrent situation if only a 3.3v level signal is used?
    4. Could you provide more details of the test? What testing equipment was used? What test standard did the test conform to?