第一步：atmega128的片内flash分区描述
在atmega128 datasheet的275页中有分区描述

对应的在284页中，有具体的应用区与boot区的大小设置

注意：Byte address = word address * 2
这里的BOOT区首地址，$F000 = 0x1E000

根据手册中的描述，我们使用JTAG MKII 烧写器通过软件 Avr Studio 4，配置熔丝位 BOOTSZ为00

注意：这里面的4096 words = 8K bytes

第二步：说明一下linker(.xcl)文件的作用
好了，怎么让我们的程序烧写到flash中是在指定的0x1E000处呢？这就需要在link文件中指定CODE区的位置了。
适用于atmega128 bootloader程序的.xcl文件如下：

/*                      - lnkm128.xcl -

 *

 *   XLINK command file for the ICCAVR C-compiler using the --cpu=m128, -ms

 *   options. Segments are defined for an ATmega128 whithout external

 *   memory. It is also possible to "add" external SRAM, EPROM and EEPROM.

 *

 *   Usage: xlink your_file(s) -f lnkm128

 *

 *   File version:   $Name: $

 */

/*========================================================================*/

/* NOTE: This file has been modified to be used with the code example in: */

/*    AVR106: C functions for reading and writing to Flash memory         */

/* Se comments further down in this file, and the application note for    */

/* more information.                                                      */

/*========================================================================*/

/*====================================================*/

/* 

 * Constants used down below, 

 * Do not change these lines, 

 * if it is not stated otherwise 

 */

/* Code (flash) segments */

-D_..X_INTVEC_SIZE=8C   /* 4 bytes * 35 vectors */

-D_..X_FLASH_TEND=FF    /* End of tiny flash memory */

-D_..X_FLASH_NEND=FFFF  /* End of near flash memory */

-D_..X_FLASH_END=1FFFF  /* End of flash memory */

/* Internal data memory */

/* 

 * Change the two lines below to 60(BASE) and FF(TEND) 

 * if you are running in "mega103 mode" 

 */

-D_..X_SRAM_BASE=100    /* Start of ram memory */

-D_..X_SRAM_TEND=100    /* End of tiny ram memory */

-D_..X_SRAM_END=10FF    /* End of ram memory */

/* Internal EEPROM */

-D_..X_EEPROM_END=FFF   /* End of eeprom memory */

/*====================================================*/

/*

 * Modify the lines below to alter the size of the RSTACK, CSTACK and HEAP

 * segments. These need to be fine tuned to suit your specific application.

 * The '_..X_' prefix is used by C-SPY as an indication that the label should

 * not be displayed in the dissassembly window.

 */

//-D_..X_CSTACK_SIZE=200  /* 512 bytes for auto variables and saved registers. */

//-D_..X_RSTACK_SIZE=40   /* 64 bytes for return addresses, equivalent to 32 */

                        /* levels of calls, including interrupts. */

//-D_..X_HEAP_SIZE=100    /* 256 bytes of heap. */

-D_..X_CSTACK_SIZE=300  /* 512 bytes for auto variables and saved registers. */

-D_..X_RSTACK_SIZE=40   /* 64 bytes for return addresses, equivalent to 32 */

                        /* levels of calls, including interrupts. */

-D_..X_HEAP_SIZE=100    /* 256 bytes of heap. */

/*

 * Modify these lines if you have an external SRAM connected to the system.

 *

 * Note: Remember to turn on the external data and address busses in

 *       __low_level_init if external memory is used.

 */

-D_..X_EXT_SRAM_BASE=_..X_SRAM_BASE

-D_..X_EXT_SRAM_END=_..X_SRAM_END

/*

 * Modify these lines if you have an external EPROM connected to the system.

 *

 * Note: Remember to turn on the external data and address busses in

 *       __low_level_init if external memory is used.

 */

-D_..X_EXT_EPROM_BASE=_..X_SRAM_BASE

-D_..X_EXT_EPROM_END=_..X_SRAM_END

/*

 * Modify these lines if you have an external EEPROM connected to the system.

 *

 * Note: Remember to turn on the external data and address busses in

 *       __low_level_init if external memory is used.

 */

-D_..X_EXT_EEPROM_BASE=_..X_SRAM_BASE

-D_..X_EXT_EEPROM_END=_..X_SRAM_END

/*

 * The following segments are located in the internal memory of

 * the ATmega128. Do not change these lines.

 */

/* Define CPU */

-ca90

/*========================================================================*/

/* How to move the complete project and interrupt table to a Boot Sector. */

/*========================================================================*/

/* This method can be used on any device with boot sectors.               */

/* It presumes these defines are predefined:                              */

/*     _..X_INTVEC_SIZE, _..X_FLASH_TEND,                                 */

/*     _..X_FLASH_NEND, _..X_FLASH_END                                    */

/*========================================================================*/

/* -1- Find and remove (/comment out) the following section from the      */

/*     original XCL file.                                                 */

/*========================================================================*/

/* Code memory */

//-Z(CODE)INTVEC=0-(_..X_INTVEC_SIZE-1)

/* Fill unused interrupt vector's with RETI */

/*

-H1895

-h(CODE)0-_..X_INTVEC_SIZE

-Z(CODE)TINY_F=_..X_INTVEC_SIZE-_..X_FLASH_TEND

-Z(CODE)NEAR_F,SWITCH,DIFUNCT=_..X_INTVEC_SIZE-_..X_FLASH_NEND

-Z(CODE)CODE=_..X_INTVEC_SIZE-_..X_FLASH_END

-Z(FARCODE)FAR_F=_..X_INTVEC_SIZE-_..X_FLASH_END

-Z(CODE)HUGE_F,INITTAB=_..X_INTVEC_SIZE-_..X_FLASH_END

-Z(CODE)TINY_ID,NEAR_ID,CHECKSUM=_..X_INTVEC_SIZE-_..X_FLASH_END

*/

/*========================================================================*/

/* -2- Paste in the following section as a replacement.                   */

/* -3- Remove the comment marking on the used Boot Sector Size            */

/*========================================================================*/

/* Boot Sector Size */

-D_..X_BOOTSEC_SIZE=2000  /* 4096 words  */

//-D_..X_BOOTSEC_SIZE=1000  /* 2048 words */

//-D_..X_BOOTSEC_SIZE= 800  /* 1024 words */

//-D_..X_BOOTSEC_SIZE= 400  /*  512 words */

//-D_..X_BOOTSEC_SIZE= 200  /*  256 words */

//-D_..X_BOOTSEC_SIZE= 100  /*  128 words */

-D_..X_DEFSEC_POS=1000

/* Code memory */

-Z(CODE)INTVEC=(_..X_FLASH_END-_..X_BOOTSEC_SIZE+1)-(_..X_FLASH_END-_..X_BOOTSEC_SIZE+_..X_INTVEC_SIZE) 

-Z(CODE)DEFSEC=(_..X_FLASH_END-_..X_BOOTSEC_SIZE+1+_..X_DEFSEC_POS)-_..X_FLASH_END

/* Fill unused interrupt vector's with RETI */

-H1895

-h(CODE)(_..X_FLASH_END-_..X_BOOTSEC_SIZE+1)-(_..X_FLASH_END-_..X_BOOTSEC_SIZE+_..X_INTVEC_SIZE) 

/*========================================================================*/

/* -4- If the flash size is 32kB or less then;                            */

/*     - Remove the comment marking on following line:                    */

/*========================================================================*/

//-Z(CODE)NEAR_F,SWITCH,DIFUNCT=(_..X_FLASH_END-_..X_BOOTSEC_SIZE+_..X_INTVEC_SIZE+1)-_..X_FLASH_NEND

/*========================================================================*/

/* -5- If the flash size is 32kB or less then;                            */

/*     - Remove the SWITCH segment from the following line:               */

/*========================================================================*/

-Z(CODE)CODE,SWITCH=(_..X_FLASH_END-_..X_BOOTSEC_SIZE+_..X_INTVEC_SIZE+1)-_..X_FLASH_END

-Z(FARCODE)FAR_F=(_..X_FLASH_END-_..X_BOOTSEC_SIZE+_..X_INTVEC_SIZE+1)-_..X_FLASH_END

-Z(CODE)HUGE_F,INITTAB=(_..X_FLASH_END-_..X_BOOTSEC_SIZE+_..X_INTVEC_SIZE+1)-_..X_FLASH_END

-Z(CODE)TINY_ID,NEAR_ID,CHECKSUM=(_..X_FLASH_END-_..X_BOOTSEC_SIZE+_..X_INTVEC_SIZE+1)-_..X_FLASH_END

/*========================================================================*/

/*========================================================================*/

/* Internal data memory */

-Z(DATA)TINY_I,TINY_Z,TINY_N=_..X_SRAM_BASE-_..X_SRAM_TEND

-Z(DATA)NEAR_I,NEAR_Z=_..X_SRAM_BASE-_..X_SRAM_END,_..X_EXT_SRAM_BASE-_..X_EXT_SRAM_END

/*

 * If external SRAM is available it is possible to place the stacks there.

 * However, the external memory is slower than the internal so moving the

 * stacks to the external memory will degrade the system performance.

 */

-Z(DATA)RSTACK+_..X_RSTACK_SIZE=_..X_SRAM_BASE-_..X_SRAM_END /* ,_..X_EXT_SRAM_BASE-_..X_EXT_SRAM_END */

-Z(DATA)CSTACK+_..X_CSTACK_SIZE=_..X_SRAM_BASE-_..X_SRAM_END /* ,_..X_EXT_SRAM_BASE-_..X_EXT_SRAM_END */

/*

 * If external SRAM is available it might be a good idea to move the

* heap segment there, i.e. rem