Atmel CAVR-4 Manual De Usuario

CAVR-4

Part 1. Using the compiler

In the linker command file it can look like this:

-Z(CODE)CODE=0-1FFF

If you create your own segments—see Controlling data and function placement, page 
47—these must also be defined in the linker command file using the 

-Z

 or 

-P

 segment 

control directives. In the linker command file it can look like this:

-Z(CODE)MYSEGMENT=100-2FF

The compiler uses a set of internally generated segments, which are used for storing 
information that is vital to the operation of the program.

●

The 

SWITCH

 segment which contains data statements used in the switch library 

routines. These tables are encoded in such a way as to use as little space as possible.

●

The 

INITTAB

 segment contains the segment initialization description blocks that 

are used by the 

_ _segment_init

 function which is called by 

CSTARTUP

. This table 

consist of a number of 

SegmentInitBlock_Type

 objects. This type is declared in 

the 

segment_init.h

 file which is located in the 

avr\src\lib

 directory.

●

The 

DIFUNCT

 segment is only used when a source file has been compiled in C++ 

mode and the file contains global objects (class instances). The segment will then 
contain a number of function pointers that point to constructor code that should be 
performed for each object.

In the linker command file it can look like this:

-Z(CODE)SWITCH,INITTAB,DIFUNCT=0-1FFF

This section lists several features and methods to help you manage memory and 
segments. 

The 

@

 operator, alternatively the 

#pragma location

 directive, can be used for placing 

global and static variables at absolute addresses. The syntax can also be used for placing 
variables or functions in named segments. The variables must be declared either 

_ _no_init

 or 

const

. If declared 

const

, it is legal for them to have initializers. The 

named segment can either be a predefined segment, or a user-defined segment.