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ICCAVR port

Posted by Nobody/Anonymous on November 9, 2006
I've tried to make a FreeRTOS port for imagecraft's ICCAVR compiler, but i can't it get to work in avrstudio simulator. I don't understand, what should functions portENTER_CRITICAL() and portEXIT_CRITICAL() to do, because in both ports are they quite different.
Has anyone already done port to iccavr?
Please help me
pbr(@)pobox(.)sk

RE: ICCAVR port

Posted by Nobody/Anonymous on November 9, 2006
Enter and exit critical should always do the same thing or at least have the same effect. Which two ports are you comparing?

RE: ICCAVR port

Posted by Nobody/Anonymous on November 10, 2006
the IAR port has this:
void vPortEnterCritical( void )
{
portDISABLE_INTERRUPTS();
uxCriticalNesting++;
}

void vPortExitCritical( void )
{
uxCriticalNesting--;
if( uxCriticalNesting == portNO_CRITICAL_NESTING )
{
portENABLE_INTERRUPTS();
}
}

and the GCC port:
#define portENTER_CRITICAL()
asm ( "in__tmp_reg__, 0x3F" );\
asm ( "cli" );\
asm ( "push__tmp_reg__" )

#define portEXIT_CRITICAL()
asm ( "pop__tmp_reg__" );\
asm ( "out0x3F, __tmp_reg__" )



RE: ICCAVR port

Posted by Nobody/Anonymous on November 10, 2006
These effectively do the same thing.

The idea is not to nest calls. In other words if you call:

portENTER_CRITICAL();
portENTER_CRITICAL();
portEXIT_CRITICAL();
portEXIT_CRITICAL();

interrupts are not reenabled until the second call to portEXIT_CRITICAL().

The GCC port does this by pushing the status flags onto the stack within each call to portENTER_CRITICAL(). A second or third call to portENTER_CRITICAL() will already have interrupts disabled when the flags are pushed, so popping the flags will not re enable interrupts again until the first push is popped.

The IAR port simply keeps a count of the number of time portENTER_CRITICAL() is called, and does not re-enable interrupts until the count reaches zero. The count has to be stored as part of the task context as each task has its own count.

RE: ICCAVR port

Posted by Nobody/Anonymous on November 11, 2006
OK,thank you for explaining.
I've found in meantime, that a port to iccavr exists. This is at http://www.dragonsgate.net/icc_forums/showthread.php?t=3&highlight=freertos,
but i cant download it. I've registered there, but i'm still not able to download it. Deos anyone have that file?


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