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[docs] rework software/makefile/linker sections

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stnolting 2024-10-20 20:29:46 +02:00
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34
docs/datasheet/software.adoc
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@ -362,45 +362,39 @@ relevant for the executable itself; the remaining sections are just listed for c
| `io` | Address space for the processor-internal IO/peripheral devices
|=======================
[NOTE]
The `rom` section is automatically re-mapped to the processor-internal <<_bootloader_rom_bootrom>> when compiling the
bootloader sources.
Each section has two main attributes: `ORIGIN` and `LENGTH`. `ORIGIN` defines the base address of the according section
while `LENGTH` defines its size in bytes. For the `ram` and `rom` sections these attributes are configured indirectly
via variables that provide default values.
via variables that already provide _default values_:
.Linker script - section configuration
[source]
----
/* Default rom/ram (IMEM/DMEM) sizes */
__neorv32_rom_size = DEFINED(__neorv32_rom_size) ? __neorv32_rom_size : 2048M;
__neorv32_rom_size = DEFINED(__neorv32_rom_size) ? __neorv32_rom_size : 16k;
__neorv32_ram_size = DEFINED(__neorv32_ram_size) ? __neorv32_ram_size : 8K;
/* Default section base addresses */
/* Default rom/ram (IMEM/DMEM) base addresses */
__neorv32_rom_base = DEFINED(__neorv32_rom_base) ? __neorv32_rom_base : 0x00000000;
__neorv32_ram_base = DEFINED(__neorv32_ram_base) ? __neorv32_ram_base : 0x80000000;
----
The region size and base address configuration can be edited by the user - either by explicitly
changing the default values in the linker script or by overriding them when invoking `make`:
.Bootloader ROM
[NOTE]
The `rom` section is automatically re-mapped to the processor-internal <<_bootloader_rom_bootrom>> when compiling the
bootloader sources.
.Overriding default `rom` size configuration (configuring 4096 bytes)
The default region sizes (and base addresses) can be edited by the user when invoking `make`:
.Overriding default memory sizes (configuring 64kB IMEM and 32kB DMEM)
[source, bash]
----
$ make USER_FLAGS+="-Wl,--defsym,__neorv32_rom_size=4096" clean_all exe
$ make USER_FLAGS+="-Wl,--defsym,__neorv32_rom_size=64k -Wl,--defsym,__neorv32_ram_size=32k" clean_all exe
----
[IMPORTANT]
.Changing the default base addresses
[WARNING]
`__neorv32_rom_base` (= `ORIGIN` of the `rom` section) and `__neorv32_ram_base` (= `ORIGIN` of the `ram` section) have to
be sync to the actual memory layout configuration of the processor (see section <<_address_space>>).
[NOTE]
The default configuration for the `rom` section assumes a maximum of 2GB _logical_ memory address space. This size does not
have to reflect the _actual_ physical size of the entire instruction memory. It just provides a maximum limit. When uploading
a new executable via the bootloader, the bootloader itself checks if sufficient _physical_ instruction memory is available.
If a new executable is embedded right into the internal-IMEM the synthesis tool will check, if the configured instruction memory
size is sufficient.
be match the actual processor memory layout configuration of the processor (see section <<_address_space>>).
The linker maps all the regions from the compiled object files into five final sections: `.text`,
`.rodata`, `.data`, `.bss` and `.heap`: