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3 Porting a BSP to Custom Hardware

3.2 Getting a Minimal Kernel Running

ROM as early as possible and thus save download cycles. In this case, starting the

WDB agent before the kernel is desirable.

Keep in mind, there are several disadvantages to starting the agent before the

kernel. These are:

■

Once the hardware initialization code is written, bringing up the kernel takes

less time than bringing up the agent. Because most developers consider a

working kernel to be the more significant milestone, they usually start with the

kernel.

■

Starting the agent before the kernel is not a significant help to getting the basic

kernel working. This is because the basic kernel adds little to what you have

written already: the basic kernel adds only a timer driver and possibly an

interrupt controller, which are simple devices.

■

Starting the WDB agent before the kernel limits you to system-mode

debugging.

Starting the agent before the kernel is described in the Wind River Workbench User's

Guide for VxWorks: Setting Up Your Hardware and the VxWorks Kernel Programmer’s

Guide: Kernel. The following sections provide important additional information.

Caveats

Because the virtual I/O driver requires the kernel, add the following line to

config.h:

#undef INCLUDE_WDB_VIO

There is an important caveat if you are planning to use the target agent serial-line

communication path. When the kernel is first started, interrupts are enabled in the

processor, but driver interrupt handlers are not yet connected. You must ensure

that the serial device you use for agent communication does not generate an

interrupt. If your board has an interrupt controller, use it to mask serial interrupts

in sysHwInit( ). Be aware that the target agent attempts to use all drivers in an

“interrupt on first packet” mode. As a result, you should modify the serial driver

to refuse to go into interrupt mode, even if the agent requests that mode.

System-Mode Debugging Techniques

After you have the agent working, you can use it to debug the VxWorks image to

which it is linked. To save download time, link the VxWorks code you want to

test—driver code, in particular—into the ROM image. To avoid re-making ROMs,

consider adding hooks to your BSP and driver routines as follows:

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RAM 6.0 BUX II Series Guía de usuario Pagina 75