RAM 6.0 BUX II Series Guia do Utilizador descarregar pdf (Página 16)

VxWorks

BSP Developer’s Guide, 6.0

2.2.1 Sequence Overview

Minimally, initializing a processor consists of providing a portion of code, and

possibly some tables, that are located at the specific location in memory that the

processor “jumps” to upon reset or power-up of the target system. This code sets

the processor to a specific state, initializes memory and memory addressing,

disables interrupts, and then passes control to additional bootstrapping code.

Upon power-up or reset, the processor first jumps to the entry point in ROM,

_romInit( ). The assembly code at the jump destination sets up memory, initializes

the processor status word, and creates a temporary stack. The processor then

jumps to a C routine (romStart( ) in target/config/all/bootInit.c). A parameter in a

(cold start) and then copies the appropriate sections of ROM into RAM. If the code

in ROM is compressed, it is decompressed during the copy. Next, the processor

jumps to the VxWorks entry point in RAM.

The VxWorks entry point is _sysInit( ) in sysALib.s. This assembly routine sets the

initial hardware state (much the same as _romInit( ) does) and then jumps to

usrInit( ) in usrConfig.c. usrInit( ) is the first C routine that runs from a VxWorks

image. This routine initializes the cache, clears the block storage segment (bss) to

zero, initializes the vector table, performs board-specific initialization, and then

starts the multitasking kernel with a user-booting task.

Figure 2-1 provides an overview of the boot sequence when VxWorks is booted

from an image.

1 2 ... 11 12 13 14 15 16 17 18 19 20 21 ... 188 189

Sem comentários

RAM 6.0 BUX II Series Guia do Utilizador Página 16