I have a question about AVR-LIBC FAQ #27:
http://www.nongnu.org/avr-libc/user-manual/FAQ.html#faq_spman
"Why are interrupts re-enabled in the middle of writing the stack pointer?"
I understand that when the SEI instruction is used,
"The instruction following SEI will be executed before any pending
interrupts".
I'm fine with that. So using out __SP_H_,r29 SEI, out __SP_L_,r28 would
always be safe. Might not be what you wanted if interrupts where off.
However I have missed any Atmel documentation that says a 'out' to SREG
applies that same protection? Does that mean all 'out' instructions
delay pending interrupts, or just 'out' instructions to SREG?
What document did I miss reading?
in __tmp_reg__,__SREG__
cli
out __SP_H__,r29
out __SREG__,__tmp_reg__
out __SP_L__,r28
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