User`s guide

2 Overview of a BSP
2.4 The Development Environment
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2
An in-circuit emulator provides all the advantages of an on-chip debugging (OCD)
device and may include additional features and abilities beyond the OCD
capabilities.
The disadvantages of an in-circuit emulator include cost and limited processor
support. However, for processors with no OCD interface capability, an in-circuit
emulator is sometimes the only viable solution for finding and fixing certain
problems.
Like a logic analyzer, an in-circuit emulator is generally not cost-effective for BSP
development alone.
2.4.2 WDB Debugging Interface
When no hardware debugger is available, try to minimize the amount of time
during which you do not have access to the Wind River development tools,
particularly the Wind debug target agent (WDB agent). Because the WDB agent is
linked to the kernel, it can share initialization code with the kernel. Thus, after the
initialization code has run, you can start either the WDB agent, the VxWorks
kernel, or both.
The VxWorks WDB agent provides a powerful debugging environment and, if an
OCD device is not available, it is possible to use the WDB agent for BSP debugging.
Using the WDB agent, you can debug the VxWorks image to which it is linked. The
target agent’s linked-in approach has several advantages over the older approach
of using a ROM monitor (see Native Debug ROMs, p.45). For example:
■
There is only one initialization code module to write. In a traditional
ROM-monitor approach, you must write two initialization code modules: one
for the monitor and one for the OS. In addition, the traditional approach
requires non-standard modifications to resolve contention issues over MMU,
vector table, and device initialization.
■
The code size is smaller because VxWorks and the target agent can share
generic library routines such as memcpy( ).
■
Traditional ROM monitors debug only in system mode. The entire OS is
debugged as a single thread. The WDB agent provides, in addition to system
mode, a fully VxWorks-aware tasking mode. This mode allows debugging
NOTE: Wind River BSP developers rarely use the WDB agent for debugging.
However, when no OCD device, ROM emulator, or in-circuit emulator is available,
the WDB agent is a good choice.