C語言:如何在AVR@IAR中使用absolute address

C語言 : 如何在AVR@IAR中使用absolute address
C語言 : AVR@IAR中memory 如何分配

ABSOLUTE LOCATION
It is possible to specify the location of a variable (its absolute address)using either of the following two constructs:
1) The @ operator followed by a constant-expression.

    example: The following declaration locates PIND at address 10h

                 __no_init __io char PIND @ 0x10;

   The following declaration locates i at address 20 with the value 10:

               const int i@20=10;



2) The #pragma location directive followed by a constant-expression.

  example : The following declarations are equivalent to the previousdeclarations

               #pragma location=0x10
              __no_init __io char PIND;

             #pragma location=20
             const int i=10;


/********************************************************************************/
C語言 : AVR@IAR中memory 如何分配

舉一個實例 :

#include <ioavr.h>
__root char index_b=0x10;                           // NEAR_I   0x00000223

__root __no_init char index_c;                      // NEAR_N   0x0000028A

__root __no_init char index_d @0x100;       // ABSOLUTE 0x00000100
__root __no_init char index_e @0x101;       // ABSOLUTE 0x00000101
__root const char index_g @0x102=0x10;   // ABSOLUTE 0x00000102
                                                                        // 初始值＝0x10
__root char index_a=0x00;                            // NEAR_Z   0x00000224
__root char index_f;                                       // NEAR_Z   0x00000225
char array[100];                     // NEAR_Z   0x00000226 - 0x00000289

int main(void)
{
 int i;
    for(i=0;i<10;i++)
    {
        array[i] = 123;
    }
}

complier 完成後 segment map

                ****************************************
                *                                      *
                *      SEGMENTS IN ADDRESS ORDER       *
                *                                      *
                ****************************************


說明 :
--root : Use this option to apply the __root extended keyword to all global and static variables. This will make sure that the variables are not removed by the IAR XLINK Linker.(保證沒有使用的函數或者變數也能夠包含在目標代碼中, 不會被IAR XLINK Linker 移走)

__no_init : the keyword no_init is used for specifying that an object is not initialized. In ICCAVR __no_init can be used together with a keyword specifying any memory location,  for example:

 __near __no_init char buffer [1000];

ABSOLUTE 位址: 0X00000100 - 0X00000102
ABSOLUTE : Used for located variables. (指定的絕對位址)

NEAR_Z 位址: 0X00000224 - 0X00000289
NEAR_Z :  Holds static and global __near variables that have been declared without initial value or with zero initial values. (沒有初始值或具有"0"初始值)

NEAR_I 位址  :0X00000223          
NEAR_I  : Holds static and global __near variables that have been declared with non-zero initial values.(具有非"0"初始值)

NEAR_N 位址 : 0X0000028A        
NEAR_N : Holds static and global __near to be placed in non-volatile memory.  (存放具有非揮發性記憶體)

CSTACK 位址 :  0X00000103 - 0X00000202  //256 Bytes
CSTACK : CSTACK 資料堆疊，存放局部變數

RCSTACK位址 : 0X00000203 - 0X00000222     //32 Bytes
RCSTACK :  位址返回堆疊，堆疊函數和中斷的返回位址。

CSTACK/ RCSTACK設定

 

應用:
__root __no_init char index_d @0x100;       // ABSOLUTE 0x00000100
這種 ABSOLUTE addressing 可用于擴充I/O acceess, 亦可用于memory mapping I/O 用法。