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RM48L952: SPI analog loopback test in combination with the TPS companion chip

K De Coster
Intellectual 740 points
Part Number: RM48L952

Hi there,

We are using the RM48L952 in combination with the TPS65381Companion Chip. SPI4 of the Hercules is connected to the companion chip (connected as suggested in spna176a - interfacing TPS65381 with Hercules microcontrollers).
The RM48x Safety manual (spnu577d) advises you to do a "Boot Time/Periodic Software Test of Function Using I/O Loopback" (SPI1A/B) for which the SafeTI Diagnostic Library provides the following function:
SL_SelfTest_SPI(SPI_ANALOG_LOOPBACK_TEST, SL_SPI4);

Will this test cause problems when the TPS is connected (at boot when the TPS is in DEBUG mode and periodic when the TPS is in ACTIVE mode)?

Thanks,,

Karel

  • 0
    TI__Guru**** 196776 points
    Hello Karel,

    Usage Guideline for Input/Output Loopback:
    I/O Loopback mode should be used with caution because, in some configurations, even the receive pins will be driven with transmit data. During testing, it should be ensured that none of the SPI pins are driven by any other device connected to them. Otherwise, if analog loopback is selected in I/O Loopback mode, then testing may damage the device.

    In active mode, there is regular SPI communication to feed watchdog and answer questions, I am note sure if the loopback is needed.
  • 0 in reply to QJ Wang
    Intellectual 740 points

    Hello QJ,

    From this I am concluding it is not possible to do the SPI analog loopback test in combination with the TPS as the test might drive the SOMI pin on the Hercules (even though he is master), which is connected to the SDO pin of the TPS. This could lead to a multi-driven net causing permanent damage to pins.

    Thanks for your response.

    Best regards,

    Karel


    P.S. Congratulations on achieving Guru