Atmel CAVR-4 Manual De Usuario

CAVR-4

Memory types and memory attributes

Reference Guide

The keywords are only available if language extensions are enabled in the AVR IAR 
C/C++ Compiler.

In IAR Embedded Workbench, language extensions are enabled by default.

Use the 

-e

 compiler option to enable language extensions. See -e, page 179 for 

additional information.

For syntax information, see Extended keywords for data, page 16. For reference 
information about each keyword, see Descriptions of extended keywords, page 204.

Pointers are used for referring to the location of data. In general, a pointer has a type. 
For example, a pointer that has the type 

int

 

*

 points to an integer. 

In the AVR IAR C/C++ Compiler, a pointer also points to some type of memory. The 
memory type is specified using a keyword before the asterisk. 

For example, a pointer that points to an integer stored in farflash memory is declared by: 

int

 

_ _farflash *

 p;

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 tiny memory. Like 

p

, 

p2

 points to a character in farflash memory.

char _ _farflash * _ _tiny p2; 

Whenever possible, pointers should be declared without memory attributes. For 
example, the functions in the standard library are all declared without explicit memory 
types.

_ _generic

2 bytes

3 bytes

Data or Code

The most significant bit (MSB) 

determines whether this pointer 

points to code space (1) or data 

space (0). The small generic 

pointer is generated for the 

processor options -v0 and -v1.

32 Kbytes

8 Mbytes

_ _regvar

N/A

Data

0x4–0x0F

4 bytes