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store it to external _data_ memory and transfers CPU control to that.
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store it to external _data_ memory and transfers CPU control to that.
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:sectnums!:
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:sectnums!:
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===== Indirect Boot
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===== Indirect Boot
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The _indirect_ boot scenarios **1a** and **1b** use the processor-internal <<_bootloader>>. This general setup is enabled
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The _indirect_ boot scenarios **1a** and **1b** use the processor-internal <<_bootloader>>. This boot setup is enabled
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by setting the <<_int_bootloader_en>> generic to true, which will implement the processor-internal <<_bootloader_rom_bootrom>>.
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by setting the <<_int_bootloader_en>> generic to _true_, which will implement the processor-internal <<_bootloader_rom_bootrom>>.
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This read-only memory is pre-initialized during synthesis with the default bootloader firmware.
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This read-only memory is pre-initialized during synthesis with the default bootloader firmware.
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The bootloader provides several options to upload an executable (via UART or from external SPI flash) and copies it to
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the beginning of the _instruction address space_ so the CPU can execute it.
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The bootloader provides several options to upload an executable (via UART or from external SPI flash) and store it to
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Boot scenario **1a** uses the processor-internal IMEM
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the _instruction address space_ so the CPU can execute it. Boot scenario **1a** uses the processor-internal IMEM
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(<<_mem_int_imem_en>> = _true_). This scenario implements the internal <<_instruction_memory_imem>> as non-initialized
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(<<_mem_int_imem_en>> = _true_). This scenario implements the internal <<_instruction_memory_imem>> as non-initialized
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RAM so the bootloader can write the actual executable to it.
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RAM so the bootloader can copy the actual executable to it.
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Boot scenario **1b** uses a processor-external IMEM (<<_mem_int_imem_en>> = _false_) that is connected via the processor's
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Boot scenario **1b** uses a processor-external IMEM (<<_mem_int_imem_en>> = _false_) that is connected via the processor's
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bus interface. In this scenario the internal <<_instruction_memory_imem>> is not implemented at all and the bootloader will
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bus interface. In this scenario the internal <<_instruction_memory_imem>> is not implemented at all and the bootloader will
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write the executable to the processor-external memory.
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copy the executable to the processor-external memory. Hence, the external memory has to be implemented as RAM.
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:sectnums!:
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:sectnums!:
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===== Direct Boot
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===== Direct Boot
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The _direct_ boot scenarios **2a** and **2b** do not use the processor-internal bootloader. Hence, the <<_int_bootloader_en>>
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The _direct_ boot scenarios **2a** and **2b** do not use the processor-internal bootloader since the <<_int_bootloader_en>>
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generic is set _false_. In this configuration the <<_bootloader_rom_bootrom>> is not implemented at all and the CPU will
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generic is set _false_. In this configuration the <<_bootloader_rom_bootrom>> is not implemented at all and the CPU will
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directly begin executing code from the instruction address space after reset. A "pre-initialization mechanism is required
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directly begin executing code from the beginning of the instruction address space after reset. An application-specific
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in order to provide an executable _in_ memory.
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"pre-initialization" mechanism is required in order to provide an executable _in_ memory.
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Boot scenario **2a** uses the processor-internal IMEM (<<_mem_int_imem_en>> = _true_) that is implemented as _read-only memory_
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Boot scenario **2a** uses the processor-internal IMEM (<<_mem_int_imem_en>> = _true_) that is implemented as _read-only memory_
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in this scenario. It is pre-initialized (by the bitstream) with the actual application executable.
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in this scenario. It is pre-initialized (by the bitstream) with the actual application executable during synthesis.
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In contrast, boot scenario **2b** uses a processor-external IMEM (<<_mem_int_imem_en>> = _false_). In this scenario the
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In contrast, boot scenario **2b** uses a processor-external IMEM (<<_mem_int_imem_en>> = _false_). In this scenario the
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system designer is responsible for providing a initialized external memory that contains the actual application to be executed.
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system designer is responsible for providing an initialized external memory that contains the actual application to be executed.
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If the external is not already initialized after reset, a simple ROM containing a "polling loop" can be implemented that is
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exited as soon as the application logic has finished initializing the memory with the acutal application code.
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// ####################################################################################################################
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// ####################################################################################################################
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