Subversion Repositories neorv32

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==== Bootloader ROM (BOOTROM)

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|=======================
| Hardware source file(s): | neorv32_boot_rom.vhd | 
| Software driver file(s): | none             | _implicitly used_
| Top entity port:         | none             | 
| Configuration generics:  | _BOOTLOADER_EN_ | implement processor-internal bootloader when _true_
| CPU interrupts:          | none             | 
|=======================

As the name already suggests, the boot ROM contains the read-only bootloader image. When the bootloader
is enabled via the _BOOTLOADER_EN_ generic it is directly executed after system reset.

The bootloader ROM is located at address 0xFFFF0000. This location is fixed and the bootloader ROM size
must not exceed 32kB. The bootloader read-only memory is automatically initialized during synthesis via the
`rtl/core/neorv32_bootloader_image.vhd` file, which is generated when compiling and installing the
bootloader sources.

The bootloader ROM address space cannot be used for other applications even when the bootloader is not
implemented.

**Boot Configuration**

If the bootloader is implemented, the CPU starts execution after reset right at the beginning of the boot
ROM. If the bootloader is not implemented, the CPU starts execution at the beginning of the instruction
memory space (defined via `ispace_base_c` constant in the `neorv32_package.vhd` VHDL package file,
default `ispace_base_c` = 0x00000000). In this case, the instruction memory has to contain a valid
executable – either by using the internal IMEM with an initialization during synthesis or by a user-defined
initialization process.

[TIP]
See section <<_bootloader>> for more information regarding the bootloader's boot process and configuration options.