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VxWorks

BSP Developer’s Guide, 6.0

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Initializing Interrupt Vectors—The exception vectors must be initialized before

enabling interrupts and starting the kernel. First, intVecBaseSet( ) is called to

establish the vector table base address.

After intVecBaseSet( ) is called, the routine excVecInit( ) initializes all

exception vectors to default handlers. These handlers safely trap and report

exceptions caused by program errors or unexpected hardware interrupts.

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Initializing System Hardware to a Quiescent State—Calling the

system-dependent routine sysHwInit( ) initializes the system hardware.

Initialization mainly consists of resetting and disabling hardware devices.

Otherwise, when the kernel is started and interrupts are enabled, these devices

can cause unexpected interrupts.

In VxWorks, ISRs (for I/O devices, system clocks, and so on) are not connected

to their interrupt vectors until system initialization is completed by the

usrRoot( ) task. This is a requirement because the memory pool is not yet

initialized. You must not connect an interrupt handler to an interrupt during

the sysHwInit( ) call—doing so requires memory allocation, which is not

available at this time. Most interrupt connection occurs later in the

sysHwInit2( ) routine located in sysLib.c.

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Calling kernelInit( )—The VxWorks libraries contain the code for

kernelInit( ). Therefore, it is not normally available to BSP developers in

source form. The kernelInit( ) routine initiates the multitasking environment

and never returns. It takes the following parameters:

– the address of the routine to be spawned as the “root” task, typically

usrRoot( )

– the stack size

– the start of usable memory; that is, the memory after the main text, data,

and bss segments of the VxWorks image. All memory after this area is

NOTE: The intVecBaseSet( ) routine is not called first on all architectures. For

more information, see the appropriate VxWorks Architecture Supplement.

NOTE: Take care to ensure that all interrupts are disabled. A typical problem

during BSP development is that an interrupt is not correctly disabled in

sysHwInit( ). When this happens, the system can hang once interrupts are

enabled in usrInit( ) and it can be difficult to determine the cause of the

problem.

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RAM 6.0 BUX II Series Guía de usuario Pagina 26