• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 33 subscribers
  • Views 425 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TCAN1145-Q1: The TCAN1145 chip was incorrectly awakened by a non-wake frame

MINYI ZHU
Prodigy 10 points
Part Number: TCAN1145-Q1

When the TCAN1145 chip is used, it is found that the non-wake up message is sent before power-on.

The chip will wake up immediately after power-on. The register with address 51h is read and CANINT is set to 1.

1、When the TCAN chip is completely powered down（Suspected chip reset），

2、Power on，

3、The wake up ID configured for the previous sleep does not take effect. The wake up is generated by any packet. The wake up source is detected as a packet wake up,

4、Obtain addresses 32H,33H,37H,38H3 register value is 0, VCC,VSUP voltage is < 1V, suspected chip reset, resulting in the register value is cleared,

      so the wake up configuration does not take effect,

5、Testing NXP's TJA1145 chip did not find such a false wake-up phenomenon.

Q：

1、Is the TCAN chip awakened by a non-wake message because of chip reset?

2、The reason why TJA1145 does not appear abnormal is that the CAN wake register is set to 0 after reset, so it does not wake up by messages. Does TCAN also have the same register？

Thank you!

  • 0
    TI__Guru 53555 points

    Hi Minyi,

    Thanks for sharing your question. 

    When the Vsup supply for TCAN1145 falls below the POR value all of the register values will return to their default state as listed in the corresponding register description. The default value of the CANINT bit is 0 after a POR, so I expect that this bit value would be 0 when power is first applied. After initial power up, the TCAN1145 will enter standby mode with the low power WUP receive active. Because the SW is not enabled by default, the device will react to any WUP the CAN bus by setting the CANINT flag. Therefore if there is CAN traffic while the TCAN1145 is being powered on, it is likely that the CANINT flag will be set before the MCU is able to read the register values for the first time. 

    In your testing, is the CAN bus active during the power up sequence of the TCAN1145? 

    Do any register values besides the CANINT field seem to retain their values after the POR?

    Regards, 
    Eric Schott 

  • 0 in reply to Eric Schott1
    Prodigy 10 points

    HI Eric,

    Q:In your testing, is the CAN bus active during the power up sequence of the TCAN1145? 

    →Yes, when the chip is powered off, there are always non-wake ID packets on the bus. In this case, the chip will be woken up when it is powered on.

    Do any register values besides the CANINT field seem to retain their values after the POR?

    →So far, the following 5 registers have been confirmed: 32H,33H,37H,38H, 51H,No other register is set to 1.

    Q:

    1、Is CANINT set to 1 because the bus receives a message during power-on, which is considered as bus wake-up?

    2、Does the TCAN chip have a wake up enable register and ignore the wake up source after the chip is reset?

    Regards,

    Minyi Zhu 

  • 0 in reply to MINYI ZHU
    TI__Guru 53555 points

    Hi Minyi,

    MINYI ZHU said:
    1、Is CANINT set to 1 because the bus receives a message during power-on, which is considered as bus wake-up?

    Yes, this sounds like the correct explanation. Because there is CAN traffic while the transceiver is in standby mode (right after power on), this will set the CANINT flag.

    MINYI ZHU said:
    2、Does the TCAN chip have a wake up enable register and ignore the wake up source after the chip is reset?

    In order to ignore the WUP on the CAN bus, TCAN1145 will need to be configured for partial networking. This will not be possible right after a POR, so the MCU should be programmed to ignore the CANINT flag if the PWRON flag is also set if it is desired to move back to a low power mode in this case. 

    Regards, 
    Eric Schott