RTEMS 4.5.0 On-Line Library

Initialization Code Start Code - Assembly Language Initialization

BSP and Device Driver Development Guide

7.3.1: Start Code - Assembly Language Initialization

The assembly language code in the directory start is the first part of the application to execute. It is responsible for initializing the processor and board enough to execute the rest of the BSP. This includes:

initializing the stack
zeroing out the uninitialized data section .bss
disabling external interrupts
copy the initialized data from ROM to RAM

The general rule of thumb is that the start code in assembly should do the minimum necessary to allow C code to execute to complete the initialization sequence.

The initial assembly language start code completes its execution by invoking the shared routine boot_card().

The label (symbolic name) associated with the starting address of the program is typically called start. The start object file is the first object file linked into the program image so it is insured that the start code is at offset 0 in the .text section. It is the responsibility of the linker script in conjunction with the compiler specifications file to put the start code in the correct location in the application image.

BSP and Device Driver Development Guide