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ATmegaxxxx - clarify initial stack setup

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This commit is contained in:
Phillip Stevens 2020-04-11 18:37:00 +10:00
parent 10fcd90af1
commit 62682ebe5b
1 changed files with 23 additions and 30 deletions
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23
portable/GCC/ATmegaxxxx/port.c
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@ -542,6 +542,14 @@ uint16_t usAddress;
/* The start of the task code will be popped off the stack last, so place /* The start of the task code will be popped off the stack last, so place
it on first. */ it on first. */
usAddress = ( uint16_t ) pxCode;
*pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
pxTopOfStack--;
usAddress >>= 8;
*pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
pxTopOfStack--;
#if defined(__AVR_3_BYTE_PC__) #if defined(__AVR_3_BYTE_PC__)
/* The AVR ATmega2560/ATmega2561 have 256KBytes of program memory and a 17-bit /* The AVR ATmega2560/ATmega2561 have 256KBytes of program memory and a 17-bit
* program counter. When a code address is stored on the stack, it takes 3 bytes * program counter. When a code address is stored on the stack, it takes 3 bytes
@ -553,24 +561,9 @@ uint16_t usAddress;
* In order to do this properly, we would need to get a full 3-byte pointer to * In order to do this properly, we would need to get a full 3-byte pointer to
* pxCode. That requires a change to GCC. Not likely to happen any time soon. * pxCode. That requires a change to GCC. Not likely to happen any time soon.
*/ */
usAddress = ( uint16_t ) pxCode;
*pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
pxTopOfStack--;
usAddress >>= 8;
*pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
pxTopOfStack--;
*pxTopOfStack = 0; *pxTopOfStack = 0;
pxTopOfStack--; pxTopOfStack--;
#else
usAddress = ( uint16_t ) pxCode;
*pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
pxTopOfStack--;
usAddress >>= 8;
*pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
pxTopOfStack--;
#endif #endif
/* Next simulate the stack as if after a call to portSAVE_CONTEXT(). /* Next simulate the stack as if after a call to portSAVE_CONTEXT().