Hello @nirmal_masilamani,
But when i flash the code in debug flash, its running properly. With power on reset, core 0 is hanging.
This is most likely caused by ECC RAM error. Usually, debuggers initialize the ECC on volatile memories, however, when powering on and off, debugger does not initialize RAM, and hardfault occurs when trying to access memory.
This is usually done in the startup code, before main.
The section should be also configured as non-cacheable.
Regarding your second issue: but when i try to access it from timer ISR or OS task, core 0 going to hardfault.
You can try to trace back your hardfault. Halt the core in the HardFault_Handler(), and find the SP value in the core registers: How To Debug A Fault Exception On ARM Cortex-M(V7M) MCU(S32K3XX).
Best regards,
Julián