RAM 6.0 BUX II Series Guía de usuario descargar pdf (Pagina 24)

VxWorks

BSP Developer’s Guide, 6.0

The purpose of this routine is to initialize the CPU and some portion of memory. It

does the absolute minimum amount of initialization—that is, the initialization of

essential hardware only—before jumping to romStart( ). If romInit( ) is working

correctly, the memory from

LOCAL_MEM_LOCAL_ADRS through

(

LOCAL_MEM_LOCAL_ADRS + LOCAL_MEM_SIZE) should be readable and

writable. If this is not the case, romInit( ) is not working properly.

In addition to initializing memory as described above, the romInit( ) routine must

also disable interrupts and clear caches. romInit( ) then configures the boot type

(cold or warm) to be a subroutine argument and branches to romStart( ) in

bootInit.c. For more information on configuring the boot type, see 2.3.7 Hardware

Considerations, p.42.

romInit( ) must do only as much device setup as is required to start executing C

code. Hardware initialization is the responsibility of the sysHwInit( ) routine in

target/config/sysLib.c, which is called later during the boot sequence.

Step 2: Execute romStart( )

The purpose of the romStart( ) routine is to move all further bootstrap code from

ROM into RAM and then, if necessary, jump to the VxWorks image. Because this

implementation depends only on the CPU architecture, the romStart( ) routine is

provided by Wind River and is located in the file bootInit.c. Typically, romStart( )

jumps to the usrInit( ) routine in RAM.

The required execution steps are as follows:

1. Copy the data segment from flash to ROM. Depending on the image type, you

may also need to copy the text segment. If necessary, decompress the data

during the copy.

2. Clear unused RAM.

3. The romStart( ) routine then jumps to the RAM entry point, sysInit( ), which

is located in sysALib.s. The boot type (cold or warm) is passed as an argument

to sysInit( ).

Step 3: Execute sysInit( )

The sysInit( ) routine is the RAM entry point. sysInit( )—which should be the first

routine defined in sysALib.s—invalidates caches if applicable, initializes the

system interrupt tables with default stubs, initializes the system fault tables with

default stubs, and initializes all processor registers to known default values. The

routine also enables tracing, clears all pending interrupts, and finally invokes

usrInit( ) with the argument bootType.

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RAM 6.0 BUX II Series Guía de usuario Pagina 24