Atmel CAVR-4 Manual De Usuario

CAVR-4

Part 2. Compiler reference

The AVR IAR C/C++ Compiler adheres to these rules for all 8-bit types.

The following object types are treated in a special way:

For all combinations of object types not listed, only rule number one applies.

In C++, all plain C data types are represented in the same way as described earlier in this 
chapter. However, if any Embedded C++ features are used for a type, no assumptions 
can be made concerning the data representation. This means, for example, that it is not 
legal to write assembler code that accesses class members.

Global register variables

Treated as a non-triggering volatile

_ _io

 declared variables located

in 0x–0x1F

An assignment to a bitfield always generates a write access, in 

some cases also a read access. If only one bit is updated—set 

or cleared—the sci/cbi instructions are executed.