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author | Amar Takhar <amar@rtems.org> | 2016-01-16 19:08:48 -0500 |
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committer | Amar Takhar <verm@darkbeer.org> | 2016-05-02 20:51:23 -0400 |
commit | 6733466adf26030f781c2779747472150238cadd (patch) | |
tree | 3d04d21658ddf18562cefa4d9c8f18dd1d6b4459 /porting/cpu_init.rst | |
parent | Fix markup (diff) | |
download | rtems-docs-6733466adf26030f781c2779747472150238cadd.tar.bz2 |
Split document into seperate files by section.
Diffstat (limited to 'porting/cpu_init.rst')
-rw-r--r-- | porting/cpu_init.rst | 51 |
1 files changed, 51 insertions, 0 deletions
diff --git a/porting/cpu_init.rst b/porting/cpu_init.rst new file mode 100644 index 0000000..0406c35 --- /dev/null +++ b/porting/cpu_init.rst @@ -0,0 +1,51 @@ +CPU Initialization +################## + +This section describes the general CPU and system initialization sequence +as it pertains to the CPU dependent code. + +Introduction +============ + +XXX general startup sequence description rewritten to make it more +applicable to CPU depdent code in executive + +Initializing the CPU +==================== + +The _CPU_Initialize routine performs processor dependent initialization. +.. code:: c + + void _CPU_Initialize( + void (\*thread_dispatch) /* may be ignored \*/ + ) + +The thread_dispatch argument is the address of the entry point for the +routine called at the end of an ISR once it has been decided a context +switch is necessary. On some compilation systems it is difficult to call +a high-level language routine from assembly. Providing the address of the +_Thread_ISR_Dispatch routine allows the porter an easy way to obtain this +critical address and thus provides an easy way to work around this +limitation on these systems. + +If you encounter this problem save the entry point in a CPU dependent +variable as shown below: +.. code:: c + + _CPU_Thread_dispatch_pointer = thread_dispatch; + +During the initialization of the context for tasks with floating point, +the CPU dependent code is responsible for initializing the floating point +context. If there is not an easy way to initialize the FP context during +Context_Initialize, then it is usually easier to save an "uninitialized" +FP context here and copy it to the task’s during Context_Initialize. If +this technique is used to initialize the FP contexts, then it is important +to ensure that the state of the floating point unit is in a coherent, +initialized state. + +.. COMMENT: COPYRIGHT (c) 1988-2002. + +.. COMMENT: On-Line Applications Research Corporation (OAR). + +.. COMMENT: All rights reserved. + |