AVR linker scripts: why start data memory at 0x60?

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I don't have much experience with linker scripts, so maybe I'm just misunderstanding something here. The LD linker script for the ATmega32u4 (avr5.x) specifies that data memory (SRAM) starts at 0x800060. I know that 0x800000 is just a special offset that the compiler uses for SRAM pointers, but why use 0x60 as the base of RAM? The ATmega32u4 datasheet shows that 0x60 is the start of external I/O registers and that SRAM actually starts at 0x100. Doesn't that mean the external I/O registers will be clobbered when the .data section is copied into SRAM?

1
linkerldavratmegalinker-scripts

1 Answers

0
votes

Apparently, this is something GCC accounts for if you invoke avr-ld through it. GCC overrides the virtual address of the .data section depending on what you passed to -mmcu=. If you link with avr-ld directly, the .data section is at the default 0x800060.