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50 lines
1.7 KiB
Perl
50 lines
1.7 KiB
Perl
@c
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@c COPYRIGHT (c) 1988-2002.
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@c On-Line Applications Research Corporation (OAR).
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@c All rights reserved.
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@chapter CPU Initialization
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This section describes the general CPU and system initialization sequence
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as it pertains to the CPU dependent code.
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@section Introduction
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XXX general startup sequence description rewritten to make it more
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applicable to CPU depdent code in executive
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@section Initializing the CPU
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The _CPU_Initialize routine performs processor dependent initialization.
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@example
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void _CPU_Initialize(
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void (*thread_dispatch) /* may be ignored */
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)
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@end example
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The thread_dispatch argument is the address of the entry point for the
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routine called at the end of an ISR once it has been decided a context
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switch is necessary. On some compilation systems it is difficult to call
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a high-level language routine from assembly. Providing the address of the
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_Thread_ISR_Dispatch routine allows the porter an easy way to obtain this
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critical address and thus provides an easy way to work around this
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limitation on these systems.
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If you encounter this problem save the entry point in a CPU dependent
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variable as shown below:
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@example
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_CPU_Thread_dispatch_pointer = thread_dispatch;
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@end example
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During the initialization of the context for tasks with floating point,
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the CPU dependent code is responsible for initializing the floating point
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context. If there is not an easy way to initialize the FP context during
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Context_Initialize, then it is usually easier to save an "uninitialized"
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FP context here and copy it to the task's during Context_Initialize. If
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this technique is used to initialize the FP contexts, then it is important
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to ensure that the state of the floating point unit is in a coherent,
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initialized state.
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