topic Re: SJA1124EVB Resets Itself After 3 Seconds in Other NXP Products

SJA1124EVB Resets Itself After 3 Seconds

appplay — Sun, 21 Sep 2025 03:26:20 GMT

Dear NXP Support Team,

I am developing a system using the SJA1124EVB together with an ESP32-S3 microcontroller.
Communication with the SJA1124 over SPI works correctly and I am able to write to its registers.

As a test, I wrote the value 0x06 to the PLLCFG register because I am using an external clock frequency of 3 MHz. When I read the register back, I correctly get 0x06. However, after approximately 3 seconds the SJA1124 resets itself and the value read from PLLCFG reverts to 0x0A. (I am reading the PLLCFG register every 100 ms.)

I have checked the power supply and it is sufficient for the system. I have also attached the test results for your reference.

Could you please advise me on how to resolve this issue?

Thank you very much for your support.

Re: SJA1124EVB Resets Itself After 3 Seconds

TomasVaverka — Thu, 25 Sep 2025 07:05:23 GMT

Dear Apichat,

This behavior is likely due to the INITI idle timeout mechanism described in Section 6.2.3 of the datasheet.

After transitioning to Normal mode, the INITI interrupt is set and must be cleared before the INITI idle timeout (tto(idle)INITI) expires. If not cleared, the device switches to Low Power mode, which resets all registers.

From Table 47, tto(idle)INITI = 2.6 to 3.4 seconds. This matches your observation of the reset occurring after ~3 seconds.

To prevent the SJA1124 from resetting, clear the INITI interrupt after entering Normal mode. Write 0x80 to the INT1 register (address 0x10) to clear bit 7 (INITI). This must be done within 3 seconds of power-up or wake-up.

BRs, Tomas

Re: SJA1124EVB Resets Itself After 3 Seconds

appplay — Thu, 25 Sep 2025 11:02:19 GMT

Dear NXP TechSupport

Thank you very much for your reply. I will follow your recommendations.

At the moment, I am also receiving support from NXP Thailand (Mr. Surasak and Mr. Wittawat), who kindly lent me the FRDM-MCXX444 board to work with the SJA1124 EVB using the code from GitHub. This has helped me understand the operation of the SJA1124 much better.

Best regards,