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AM2634-Q1: MCAL usage for ASIL-D

Sunil Joshi
Prodigy 145 points
Part Number: AM2634-Q1

Tool/software:

Hi,

1. We have tight timing requirements while using MCAL API's in our fast ISRs in motor control , When we use MCAL API's like for example: 

Pwm_SetDutyCycle(), or Adc_StartGroupConversion ()

it takes quite a lot of time upto 30 micro second to execute. So we have to write our own thin APIs to work with registers directly to meet time requirements
Are we at risk of compromising ASIL-D compliance since we are not using ASIL-D certified MCAL ?
2. Is it mandatory to use PMIC for external WD monitoring for achieving ASIL-D ? or can we still manage to achieve ASIL-D with internal WDs at core and cross core monitoring ?
Any thoughts . .?
 

Regards

Sunil

  • 0
    TI__Intellectual 2640 points

    Hello,

    Sunil Joshi said:
    Pwm_SetDutyCycle(), or Adc_StartGroupConversion ()

    it takes quite a lot of time upto 30 micro second to execute. So we have to write our own thin APIs to work with registers directly to meet time requirements

    Yes, it will risk ASIL-D certification.

    Yes, PMIC is required for external WD monitoring for achieving ASIL-D.

    Thanks,
    Gunjan

  • 0
    Prodigy 145 points

    Thanks Gunjan, could you please elaborate it more for better clarity ? We thought like this:

    1. Pwm_SetDutyCycle() is actually going to result into motor control and it is not directly responsible for safety. So we say in our complex device driver, we use our own functions that directly access registers and does the required job.

    2. Adc_StartGroupConversion () is a tricky one as we want to trigger this function every switching cycle i.e. 32.5 micro second. Problem is we can not afford any of the functions in this ISR to take longer time, since they will add CPU utilization. By nature we don't think the MCAL APIs are optimized for timing requirements of motor control ISRs. Hence we are ending up doing register access for equivalent MCAL functions. 

    3. Thanks for confirming about external WD from PMIC. We agree this is needed.

    Regards

    Sunil

  • 0 in reply to Sunil Joshi
    TI__Intellectual 2640 points

    Hello Sunil,

    Any changes in driver code will violate safety certification from TI side. You need to re-certify your code if you do so.

    You can decide whether your application need Pwm and Adc with safety constraint.

    Thanks,
    Gunjan

  • 0 in reply to Gunjan Kumari
    Prodigy 145 points

    Hi Gunjan, agree, we are _not_ modifying anything in  TI MCAL, instead in Cdd we came up with similar functions accessing registers directly. Guess this is common for motor control applications that need to be completed as quickly as possible in ISR.

  • 0 in reply to Sunil Joshi
    TI__Intellectual 2640 points

    Hello Sunil,

    If you are implementing your own Cdd, you need to re-certify it.

    Thanks,
    Gunjan