Using the 'reserved' keyword to prevent section placement

By default, the linker places sections according to the 'priority' value entered for the memory block. Memories with a higher priority value will be filled up first, and the memories will be loaded from lower to higher addresses.

Possible solution

If a certain memory range should not be used, you can apply the reserved keyword to prevent a section placement within that memory range. 

section_layout :vtc:linear
{
    group ( ordered, run_addr = mem:mpe:pflash0[0x100] )
    {
        reserved "MY_RESERVE" ( size = 16k );
    }
}

The above-listed LSL entry reserves 16 kB in pflash0 memory, starting at offset 0x100, within this memory range.

+ Space mpe:vtc:linear (MAU = 8bit)
+------------------------------------------------------------------------------------------------------------------------+
| Chip | Group | Section | Size (MAU) | Space addr | Chip addr | Alignment|
|========================================================================================================================|
|
...
| mpe:pflash0 | | MY_RESERVE (354) | 0x00004000 | 0x80000100 |0x00000100 |0x00000001|
...

If you need to place a section or some sections in a reserved range, you can add an alloc_allowed entry to the reserve group.

• To allow absolute-placed sections, use alloc_allowed=absolute.
• To allow placement of sections that are placed in a memory range, use alloc_allowed=ranged.

Here, the SPECIAL_FUNCTIONS group is placed at the absolute start address offset 0x110 in memory pflash0, which is within the reserved range.

section_layout :vtc:linear
{
    group ( ordered, run_addr = mem:mpe:pflash0[0x100] )
    {
        reserved "MY_RESERVE" ( alloc_allowed=absolute, size = 16k );
    }
    group SPECIAL_FUNCTIONS ( ordered, contiguous, run_addr = mem:mpe:pflash0[0x110] )
    {
        select ".text.file_1.func_1";
        select ".text.file_1.func_2";
    }
}

Here, the SPECIAL_FUNCTIONS group is placed in an address range, starting at offset 0x110 and ending at offset 0x200 in memory pflash0, which is within the reserved range.

section_layout :vtc:linear
{
    group ( ordered, run_addr = mem:mpe:pflash0[0x100] )
    {
        reserved "MY_RESERVE" ( alloc_allowed=ranged, size = 16k );
    }
    group SPECIAL_FUNCTIONS ( ordered, contiguous, run_addr =
    mem:mpe:pflash0[0x110..0x200] )
    {
        select ".text.file_1.func_1";
        select ".text.file_1.func_2";
    }
}

The linker-generated map file includes the following entries:

+ Space mpe:vtc:linear (MAU = 8bit)
+------------------------------------------------------------------------------------------------------------------------+
| Chip | Group | Section | Size (MAU) | Space addr | Chip addr | Alignment |
|========================================================================================================================|
...
| mpe:pflash0 | | MY_RESERVE (371) | 0x00004000 | 0x80000100 | 0x00000100 | 0x00000001 |
| mpe:pflash0 |SPECIAL_FUNCTIONS | .text.file_1.func_1 (168) | 0x00000008 | 0x80000110 | 0x00000110 | 0x00000002 |
| mpe:pflash0 |SPECIAL_FUNCTIONS | .text.file_1.func_2 (169) | 0x00000008 | 0x80000118 | 0x00000118 | 0x00000002 |
| mpe:pflash0 | |.text._c_init_entry.libcs_fpu (222)| 0x00000120 | 0x80004100 | 0x00004100 | 0x00000002 |

More resources

• TriCore Documentation - User Guide (PDF)
• TriCore Online Documentation - WebHelp
• Map File Viewer - Features - Webinar
• Linker Script Language (LSL) Tips & Tricks for TASKING TriCore Toolset - Application Note