Problems programming/starting debug session when placing custom tables at end of Flash (STM32H563)

[berait]

Hello,

I am working with an STM32H563VITx (2 MB Flash) and I am experiencing a repeatable issue when placing two custom sections (.param_defaults and .app_defaults) at the end of Flash.

The application runs as long as these sections are removed.
But when they are enabled, ST-LINK GDB server / STM32CubeProgrammer fails to erase/program the Flash during a debug session.

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Project setup

I have a bootloader located at 0x08000000 (32 KB) and the application starts at 0x08008000.
At the end of the application Flash, I place two small tables:

• .param_defaults (160 bytes)

• .app_defaults (96 bytes)

Both are aligned to 32 bytes.
My linker script computes their addresses like this:

FLASH_APP_END = FLASH_APP_START + FLASH_APP_LENGTH; FLASH_APP_TABLE_START = ((FLASH_APP_END - FLASH_APP_TABLE_LENGTH + 31) / 32) * 32; FLASH_PARAM_TABLE_START = ((FLASH_APP_TABLE_START - FLASH_PARAM_TABLE_LENGTH + 31) / 32) * 32;

These sections end up at:

.param_defaults : 0x081FFF00
.app_defaults : 0x081FFFA0

Here the sections from my List-File:

Idx Name Size VMA LMA File off Algn
0 .isr_vector 0000024c 08008000 08008000 00001000 2**0
CONTENTS, ALLOC, LOAD, READONLY, DATA
1 .text 00008ad8 0800824c 0800824c 0000124c 2**2
CONTENTS, ALLOC, LOAD, READONLY, CODE
2 .rodata 00000010 08010d24 08010d24 00009d24 2**2
CONTENTS, ALLOC, LOAD, READONLY, DATA
3 .ARM.extab 00000000 08010d34 08010d34 0000afe0 2**0
CONTENTS, READONLY
4 .ARM 00000000 08010d34 08010d34 0000afe0 2**0
CONTENTS, READONLY
5 .preinit_array 00000000 08010d34 08010d34 0000afe0 2**0
CONTENTS, ALLOC, LOAD, DATA
6 .init_array 00000004 08010d34 08010d34 00009d34 2**2
CONTENTS, ALLOC, LOAD, READONLY, DATA
7 .fini_array 00000004 08010d38 08010d38 00009d38 2**2
CONTENTS, ALLOC, LOAD, READONLY, DATA
8 .data 00000028 20000000 08010d3c 0000a000 2**2
CONTENTS, ALLOC, LOAD, DATA
9 .param_defaults 0000007c 081fff00 081fff00 0000af00 2**2
CONTENTS, ALLOC, LOAD, READONLY, DATA
10 .app_defaults 00000040 081fffa0 081fffa0 0000afa0 2**2
CONTENTS, ALLOC, LOAD, READONLY, DATA
11 .bss 00000458 20000028 20000028 0000b028 2**2
ALLOC

The  .param_defaults and .app_defaults are exactly at the very top of the 2 MB Flash.

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Observed problem

When starting a debug session in STM32CubeIDE, the ST-LINK GDB server starts programming the device but fails with:

Error: failed to download Sector[0]

Error: failed to download the File

After this, the debugging session aborts.

If I comment out the two custom sections (so nothing is placed at the Flash end), everything works normally.

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Questions

1. Is the last Flash sector of STM32H563 protected or reserved for system use?
   The error always appears when the .param_defaults and .app_defaults sections are placed in the highest Flash pages.

2. Does STM32CubeProgrammer or ST-LINK have limitations when programming data very close to the Flash upper boundary?

3. Is there an official recommended way to place application-specific data structures in the last Flash pages of the STM32H5/H56x series?
   Should a safety margin be kept from the very top of Flash?

4. Could the address rounding (ALIGN 32) cause segments to be generated beyond the real Flash limit?

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Additional information

• Device: STM32H563VITx

• Board: NUCLEO-H563ZI

• ST-LINK FW: V3J16M9

• STM32CubeIDE: 1.19.0

• TrustZone: Inactive

• Bootloader occupies first 32 KB, application starts at 0x08008000.

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What I would like to understand

I want to store persistent read-only data tables at the end of Flash.
Before I redesign the memory map, I need clarification whether:

• the very last Flash pages are writable by the user

• or they are reserved / protected / not programmable by default

• or whether this is a software limitation in CubeProgrammer / ST-LINK

Any official advice or documentation reference would be greatly appreciated.

Thank you!