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TCAN1146-Q1: INH/LIMP pin register setting and INH/LIMP pin behavior in a watchdog timeout

Kento Adachi
Expert 4285 points
Part Number: TCAN1146-Q1

Tool/software:

Hello experts,

I received some questions from a customer. Could you please answer the questions below?

1. How should we set DEVICE_CONFIG1 register when we want to use LIMP function? There are INH_DIS, INH_LIMP_SEL, LIMP_DIS registers.

What happens in the conditions below?

a. INH_DIS=0(INH enable), INH_LIMP_SEL=1(LIMP), LIMP_DIS=0(LIMP enable)

b. INH_DIS=0(INH enable), INH_LIMP_SEL=1(LIMP), LIMP_DIS=1(LIMP disable)

2. When we set the INH/LIMP pin as LIMP pin, how does the pin behave in a watchdog timeout with WD_ACT=00b(Turns off INH for 300 ms and sets WD interrupt)?

Does the limp pin become High-Z state for 300ms and after that limp pin becomes high as described in 10.4.7.7 of the datasheet?

Thanks,

Kento

  • 0
    TI__Guru 74252 points

    Adachi-san,

    To address your questions:

    1a) This means that the INH pin will be used as LIMP and LIMP function is enabled at that time.

    1b) This means that the INH pin will be used as LIMP and LIMP function is disabled at that time.

    2) No, this means that the INH/LIMP pin will only work as LIMP given the conditions that enable LIMP explained in the state diagram and LIMP section of the datasheet.

    Regards,

    Eric Hackett 

  • 0 in reply to Eric Hackett
    TI__Expert 4285 points

    Hello Eric,

    Thank you for your reply. I understood LIMP will always goes high and does not go low for 300ms when watchdog timeout occurs. 

    I received an additional question. If we configure the INH/LIMP pin as INH and set WD_ACT=00b(Turns off INH for 300 ms and sets WD interrupt), does it go low for 300ms only one time when the watchdog timeout continues? Or, does it go low for 300ms periodically?

    Thanks,

    Kento

  • 0 in reply to Kento Adachi
    TI__Guru 53555 points

    Hi Adachi-san,

    When configured for a 300ms pulse, the INH pin will only pulse low once if a watchdog timeout occurs. The watchdog settings will need to be reset or serviced before a second timeout can occur which would cause another 300ms pulse. 

    Regards, 
    Eric Schott

  • 0 in reply to Eric Schott1
    TI__Expert 4285 points

    Hello Eric,

    Eric Schott1 said:
    The watchdog settings will need to be reset or serviced before a second timeout can occur which would cause another 300ms pulse. 

    Could you please let us know to reset or service the watchdog? I believe we can reset the watchdog by DEVICE_RST register, is it correct? Are there other ways to reset or service the watchdog?

    Thanks,

    Kento

  • 0 in reply to Kento Adachi
    TI__Guru 53555 points

    Hi Adachi-san,

    Yes, resetting the device via the DEVICE_RST register will be reset the watchdog. The watchdog can be serviced by writing FFh to the WD_INPUT_TRIG Register (register 15h). 

    Regards, 
    Eric Schott