11e7b38f4b
it will work (so long as it is not too close to zero, and a 4 byte aligned address of course).
24 lines
1.2 KiB
Plaintext
24 lines
1.2 KiB
Plaintext
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See the top level README for information on where to find the
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schematic and programmers reference manual for the ARM processor
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on the raspberry pi. Also find information on how to load and run
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these programs.
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There are two programs here one is blinker05 and the other uart02.
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The difference from their originals is the boot code. In attempt
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to not care about where the gpu loads our program (so long as it is
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not really close to zero), the startup code looks to see if we booted
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at zero, if not, it copies the program from where it is to zero, then
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branches to zero. Some linker script items were required to make this
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work. First ram starts at 0x0000, that is where we are going to
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copy our file. Second, the size of .text is added as a variable.
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We can use this variable to connect to the startup code (vectors.s).
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The bootcode for blinker05 had another modification, since the linker
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is going to think that 0x0000 is the entry point it is going to make
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the reset_handler variable contain some number like 0x0040, so right after
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you start running that program it branches to zero which has who knows
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what code, and you are stuck. That first instruction needs to be a
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branch not an ldr pc of some linker filled in value.
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