diff options
Diffstat (limited to 'prog')
| -rw-r--r-- | prog/link.ld | 40 | ||||
| -rw-r--r-- | prog/src/startup.c | 54 |
2 files changed, 45 insertions, 49 deletions
diff --git a/prog/link.ld b/prog/link.ld index ae0988f..5c9926c 100644 --- a/prog/link.ld +++ b/prog/link.ld @@ -1,7 +1,7 @@ MEMORY { - ROM (rx) : ORIGIN = 0x00010000, LENGTH = 4K - RAM (rwx) : ORIGIN = 0x00100000, LENGTH = 4K + ROM (rx) : ORIGIN = 0x00010000, LENGTH = 4K /* (1024 words, 0x0001_0000 to 0x0001_FFFF) */ + RAM (rwx) : ORIGIN = 0x00100000, LENGTH = 4K /* (1024 words, 0x0010_0000 to 0x0010_FFFF) */ } ENTRY(_start) @@ -12,61 +12,61 @@ SECTIONS { _stext = .; . = ORIGIN(ROM); - _start = .; /* Entry point address */ - KEEP(*(.text.startup)) /* Ensure startup code is kept */ - *(.text) /* .text sections (code) */ + _start = .; /* entry point address */ + *(.text.startup) + *(.text) /* .text sections (code) */ *(.text.*) . = ALIGN(4); - _etext = .; /* End of code section, needed for copying .data */ + _etext = .; /* end of code section */ } > ROM .rodata : { - *(.rodata) /* Read-only data */ + *(.rodata) /* Read-only data */ *(.rodata.*) } > ROM .data : { - _sidata = LOADADDR(.data); /* Start address of .data section in ROM */ + _sidata = LOADADDR(.data); /* start address of .data section in ROM */ . = ALIGN(4); - _sdata = .; /* Start of .data section in RAM */ - *(.data) /* .data sections (initialized data) */ + _sdata = .; /* start of .data section in RAM */ + *(.data) /* .data sections (initialized data) */ *(.data.*) *(.sdata) /* .sdata sections (small initialized data) */ *(.sdata.*) . = ALIGN(4); - _edata = .; /* End of .data section in RAM */ + _edata = .; /* end of .data section in RAM */ } > RAM AT > ROM .bss : { . = ALIGN(4); - _sbss = .; /* Start of .bss section */ - *(.bss) /* .bss sections (zero-initialized data) */ + _sbss = .; /* start of .bss section */ + *(.bss) /* .bss sections (zero-initialized data) */ *(.bss.*) *(.sbss) /* .sbss sections (small zero-initialized data) */ *(.sbss.*) *(COMMON) . = ALIGN(4); - _ebss = .; /* End of .bss section */ + _ebss = .; /* end of .bss section */ } > RAM .heap (NOLOAD) : { . = ALIGN(4); - _sheap = .; /* Start of heap */ - . = . + 1K; /* Size of heap (adjust as needed) */ - _eheap = .; /* End of heap */ + _sheap = .; /* start of heap */ + . = . + 1K; /* size of heap */ + _eheap = .; /* end of heap */ . = ALIGN(4); } > RAM .stack (NOLOAD) : { . = ALIGN(4); - _sstack = .; /* Start of stack */ - . = . + 1K; /* Size of stack (adjust as needed) */ - _estack = .; /* End of stack */ + _sstack = .; /* start of stack */ + . = . + 1K; /* size of stack */ + _estack = .; /* end of stack */ . = ALIGN(4); } > RAM diff --git a/prog/src/startup.c b/prog/src/startup.c index 32aa131..c09f221 100644 --- a/prog/src/startup.c +++ b/prog/src/startup.c @@ -1,39 +1,35 @@ -extern unsigned int _sidata; /* Start address for the .data section in ROM */ -extern unsigned int _sdata; /* Start address for the .data section in RAM */ -extern unsigned int _edata; /* End address for the .data section in RAM */ -extern unsigned int _sbss; /* Start address for the .bss section */ -extern unsigned int _ebss; /* End address for the .bss section */ -extern unsigned int _estack; /* End address for the stack section */ +extern unsigned int _sidata; // start of .data section in ROM +extern unsigned int _sdata; // start of .data section in RAM +extern unsigned int _edata; // end of .data section in RAM +extern unsigned int _sbss; // start of .bss section +extern unsigned int _ebss; // end of .bss section +extern unsigned int _estack; // end of .stack section (stack top) -void main(void); /* The main function declaration */ -void _start(void) __attribute__((section(".text.startup"), naked)); /* The entry point */ +void main(void); // main function declaration + +void _start(void) __attribute__((section(".text.startup"), naked)); // entry point, cpu starts executing from here void _start(void) { - unsigned int *src, *dest; - - /* Copy .data section from ROM to RAM */ - src = &_sidata; /* ROM address of the .data section */ - for (dest = &_sdata; dest < &_edata;) - { - *dest++ = *src++; - } - - //while(1); + unsigned int *src, *dst; - /* Zero initialize .bss section */ - for (dest = &_sbss; dest < &_ebss;) - { - *dest++ = 0; - } + // copy .data section from ROM to RAM + src = &_sidata; + for (dst = &_sdata; dst < &_edata;) { + *dst++ = *src++; + } + // zero initialize .bss section + for (dst = &_sbss; dst < &_ebss;) { + *dst++ = 0; + } - /* Initialize stack pointer */ - asm volatile ("la sp, _estack"); + // initialize stack pointer + asm volatile ("la sp, _estack"); - /* Call the main function */ - main(); + // call main function + main(); - /* If main returns, loop forever */ - while (1); + // halt + while (1); } |