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|=======================
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|=======================
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| Hardware source file(s): | neorv32_boot_rom.vhd |
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| Hardware source file(s): | neorv32_boot_rom.vhd |
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| Software driver file(s): | none | _implicitly used_
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| Software driver file(s): | none | _implicitly used_
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| Top entity port: | none |
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| Top entity port: | none |
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| Configuration generics: | _BOOTLOADER_EN_ | implement processor-internal bootloader when _true_
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| Configuration generics: | _INT_BOOTLOADER_EN_ | implement processor-internal bootloader when _true_
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| CPU interrupts: | none |
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| CPU interrupts: | none |
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|=======================
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|=======================
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As the name already suggests, the boot ROM contains the read-only bootloader image. When the bootloader
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[NOTE]
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is enabled via the _BOOTLOADER_EN_ generic it is directly executed after system reset.
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The default `neorv32_boot_rom.vhd` HDL source file provides a _generic_ memory design that infers embedded
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memory for _larger_ memory configurations. You might need to replace/modify the source file in order to use
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platform-specific features (like advanced memory resources) or to improve technology mapping and/or timing.
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This HDL modules provides a read-only memory that contain the executable code image of the bootloader.
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If the <<_int_bootloader_en>> generic is _true_ this module will be implemented and the CPU boot address
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is modified to directly execute the code from the bootloader ROM after reset.
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The bootloader ROM is located at address `0xFFFF0000` and can occupy a address space of up to 32kB. The base
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address as well as the maximum address space size are fixed and cannot (should not!) be modified as this
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might address collision with other processor modules.
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The bootloader memory is _read-only_ and is automatically initialized with the bootloader executable image
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`rtl/core/neorv32_bootloader_image.vhd` during synthesis. The actual _physical_ size of the ROM is also
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determined via synthesis and expanded to the next power of two. For example, if the bootloader code requires
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10kB of storage, a ROM with 16kB will be generated. The maximum size must not exceed 32kB.
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The bootloader ROM is located at address 0xFFFF0000. This location is fixed and the bootloader ROM size
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.Bootloader - Software
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must not exceed 32kB. The bootloader read-only memory is automatically initialized during synthesis via the
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[TIP]
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`rtl/core/neorv32_bootloader_image.vhd` file, which is generated when compiling and installing the
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See section <<_bootloader>> for more information regarding the actual bootloader software/executable itself.
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bootloader sources.
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The bootloader ROM address space cannot be used for other applications even when the bootloader is not
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implemented.
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**Boot Configuration**
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If the bootloader is implemented, the CPU starts execution after reset right at the beginning of the boot
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ROM. If the bootloader is not implemented, the CPU starts execution at the beginning of the instruction
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memory space (defined via `ispace_base_c` constant in the `neorv32_package.vhd` VHDL package file,
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default `ispace_base_c` = 0x00000000). In this case, the instruction memory has to contain a valid
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executable – either by using the internal IMEM with an initialization during synthesis or by a user-defined
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initialization process.
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.Boot Configuration
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[TIP]
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[TIP]
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See section <<_bootloader>> for more information regarding the bootloader's boot process and configuration options.
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See section <<_boot_configuration>> for more information regarding the processor's different boot scenarios.
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See section <<_boot_configuration>> for more information regarding the processor's different boot scenarios.
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See section <<_boot_configuration>> for more information regarding the processor's different boot scenarios.
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