Tornado

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Setup and Startup
2.5 Host-Target Communication Configuration
Tornado host tools such as the shell and debugger communicate with the target
system through a target server. A target server can be configured with a variety of
back ends, which provide for various modes of communication with the target
agent. On the target side, VxWorks can be configured and built with a variety of
target agent communication interfaces.
Your choice of target server back end and target agent communication interface is
based on the mode of communication that you establish between the host and
target (network, serial, and so on). In any case, the target server must be configured
with a back end that matches the target agent interface with which VxWorks has
been configured and built. See Figure 2-4 for a detailed diagram of host-target
communications.
The default configurations for both the VxWorks target agent and Tornado target
servers are for a network connection. If you are using a network connection, you
can proceed with booting your target (2.6 Booting VxWorks, p.45).
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! WARNING: If you are using a connection other than network (the default), you
must rebuild VxWorks with the appropriate target agent communication interface,
and configure a target server with the corresponding back end, before you can use
Tornado tools with your target. See 4.6 Configuring the Target-Host Communication
Interface, p.137 and 2.5 Host-Target Communication Configuration, p.31.
All of the standard back ends included with Tornado connect to the target through
the WDB target agent. Thus, in order to understand the features of each back end,
you must understand the modes in which the target agent can execute. These
modes are called task mode, system mode, and dual mode.
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In task mode, the agent runs as a VxWorks task. Debugging is performed on a
per-task basis: you can isolate the task or tasks of interest without affecting the
rest of the target system.
In system mode, the agent runs externally from VxWorks, almost like a ROM
monitor. This allows you to debug an application as if it and VxWorks were a
single thread of execution. In this mode, when the target run-time encounters
a breakpoint, VxWorks and the application are stopped and interrupts are
locked. One of the biggest advantages of this mode is that you can single-step
through ISRs; on the other hand, it is more difficult to manipulate individual
tasks. Another drawback is that this mode is more intrusive: it adds significant
interrupt latency to the system, because the agent runs with interrupts locked
when it takes control (for example, after a breakpoint).
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