Atmel CAVR-4 Manual De Usuario

CAVR-4

Part 2. Compiler reference

#pragma bitfields

#pragma bitfields={reversed|default}

The 

#pragma

 

bitfields

 directive controls the order of bitfield members. 

By default, the AVR IAR C/C++ Compiler places bitfield members from the least 
significant bit to the most significant bit in the container type. Use the 

#pragma bitfields=reversed

 directive to place the bitfield members from the 

most significant to the least significant bit. This setting remains active until you turn it 
off again with the 

#pragma

 

bitfields=default

 directive.

#pragma constseg

The 

#pragma

 

constseg

 directive places constant variables in a named segment. Use 

the following syntax:

#pragma constseg=MY_CONSTANTS

const int factorySettings[] = {42, 15, -128, 0};

#pragma constseg=default

The segment name cannot be a predefined segment; see the chapter Segment reference 
for more information. 

The memory in which the segment resides is optionally specified using the following 
syntax:

#pragma constseg=_ _huge MyOtherSeg

All constants defined following this directive will be placed in the segment 

MyOtherSeg

 and accessed using huge addressing.

 #pragma data_alignment

#pragma data_alignment=expression

Use this pragma directive to give a variable a higher (more strict) alignment than it 
would otherwise have. It can be used on variables with static and automatic storage 
duration.

The value of the constant 

 must be a power of two (1, 2, 4, etc.).

When you use 

#pragma

 

data_alignment

 on variables with automatic storage 

duration, there is an upper limit on the allowed alignment for each function, determined 
by the calling convention used.

#pragma dataseg

The 

#pragma

 

dataseg

 directive places variables in a named segment. Use the 

following syntax:

#pragma dataseg=MY_SEGMENT 

_ _no_init char myBuffer[1000];

#pragma dataseg=default