Atmel CAVR-4 Manual De Usuario

CAVR-4

Part 1. Using the compiler

Note that the location of the pointer variable 

p

 is not affected by the keyword. In the 

following example, however, the pointer variable 

p2

 is placed in far memory. Like 

p

, 

p2

 

points to a character in EEPROM memory.

char _ _eeprom * _ _far p2; 

Storage can also be specified using type definitions. The following two declarations are 
equivalent:

typedef char _ _far Byte;

typedef Byte *BytePtr;

Byte b;

BytePtr bp; 

and

_ _far char b;

char _ _far *bp;

The AVR IAR C/C++ Compiler supports a number of memory models that can be used 
for applications with different data requirements.

Technically, the memory model specifies the default memory type attribute and default 
data pointer attribute. This means that the memory model controls the following:

●

The placement of static and global variables, as well as constant literals

●

Dynamically allocated data, for example data allocated with 

malloc

, or, in C++, 

the operator 

new

●

The default pointer type

●

The placement of the runtime stack.

The memory model only specifies the default memory type. It is possible to override this 
for individual variables and pointers. For information about how to specify a memory 
type for individual objects, see Using data memory attributes, page 19.

Three memory models are implemented: Tiny, Small, and Large. These models are 
controlled by the 

--memory_model

 option. Each memory model has a default memory 

type and a default pointer size. The code size will also be reduced somewhat if the Tiny 
or Small memory model is used.