SPC58NH92: Intermittent Cold Boot Halt When Accessing Variable in Custom .noinit Section (DRAM2)

[VRodr.2]

Hello everyone,

I am working with an SPC58NH92C5RMI0X microcontroller using SPC5Studio v6.0 and the corresponding GCC toolchain.

Objective: I am trying to implement a persistent variable that survives warm resets (debugger or pin resets) but is initialized in a controlled manner on a cold boot (power-on). To achieve this, I have created a custom .noinit section in memory.

Symptoms: The system's behavior is inconsistent and depends on the boot type:

1. Under the Debugger (Warm Resets): The system works perfectly. I can write a value to my persistent variable, perform a reset via the debugger, and the correct value is read in the next session.

2. On Power-On (Cold Boot): The system behaves erratically. Sometimes it boots correctly, but most of the time it halts/crashes.

3. Point of Failure: When the system halts, the crash occurs precisely at the instruction that attempts to read the persisted variable for the first time in my main() function.

Implementation:

To isolate the variable from the standard RAM clearing routines (_sysraminit in boot.s and the BSS clear in crt0.s), I have modified my linker script to create a dedicated memory region at the end of dram2.

1. C Code Variable:

__attribute__((section(".noinit"), used))
volatile uint32_t persisted;

int main(void) {
    // ... initializations ...

    pal_lld_setpad(PORT_LED2_KIT, LED2_KIT); // Turn on LED to indicate main has started

    // >>> THE CODE CRASHES HERE ON COLD BOOT <<<
    if (persisted == 0xdeadbeef) {
        pal_lld_setpad(PORT_LED1_KIT, LED1_KIT); // Indicates the value was read successfully
    } else {
        pal_lld_setpad(PORT_LED3_KIT, LED3_KIT); // Indicates the value was different
    }
    
    // ...
}

2. Linker Script (user.ld):

MEMORY
{
    dataflash : org = 0x00800000, len = 256k
    flash     : org = 0x00FC0000, len = 10M 
    ram       : org = 0x40028000, len = 1376k - 288k
    iram0     : org = 0x50000000, len = 32k
    iram1     : org = 0x51000000, len = 32k
    iram2     : org = 0x52000000, len = 32k
    dram0     : org = 0x50800000, len = 64k
    dram1     : org = 0x51800000, len = 64k
    dram2     : org = 0x52800000, len = 64k - 4k
    noinit_ram : org = 0x52800000 + (64k - 4k), len = 4k
}

SECTIONS
{
    /* ... other sections ... */

    .noinit (NOLOAD):
    {
        . = ALIGN(4);
        __noinit_start__ = .;
        *(.noinit)
        *(.noinit.*)
        . = ALIGN(4);
        __noinit_end__ = .;
    } > noinit_ram

    __heap_base__   = __bss_end__;
    __heap_end__    = __ram_end__;
}

Any help or insight would be greatly appreciated. Thank you.