DSP2812的FLASH虽然很大，但是程序在这个FLASH区域运行的速度与在RAM中运行速度相比要慢很多，为此通常的做法是将需要快速运行的程序copy到ram中运行，通常将中断子程序以及中断中调用的其他子程序copy到RAM中运行，对于一些不需要太快速度处理的程序可以不管，让其在FLASH中运行。
将FLASH中程序copy到RAM中的运行的RAM需要连续地址区域，而最大的连续区域仅8k，对于一些大软件来说就不够用了；扩充可用RAM区间分两个阶段，通常例程中cmd文件中的分配并未将单个8k都用起来，所以第一个阶段是将可用最大的8k RAM连起来作为一个连续区间，如下：RAML0 : origin = 0x008000, length = 0x002000 /* on-chip RAM block L0 */
同时将与其相邻的另外段RAML01屏蔽，如下：
// RAML1 : origin = 0x00A000, length = 0x000000 /* on-chip RAM block L1 */
通过以上修改可以将RAML0调整到最大的8k，这样对应着可copy子程序的ramfuncs就是8k：ramfuncs : LOAD = FLASHD, RUN = RAML0, LOAD_START(_RamfuncsLoadStart), LOAD_END(_RamfuncsLoadEnd), RUN_START(_RamfuncsRunStart), PAGE = 0
第二阶段，是将RAMH0的8k也作为可拷贝程序的区间，有一些采用了将.test拆分的方法(http://blog.sina.com.cn/s/blog_c82fc4020102wdms.html)，个人觉得太麻烦，实际上可以再定义一个ramfuncs2，采用和 ramfuncs同样的定义方式，将RUN = RAML0改为RUN = RAMH0岂不是更简单？ramfuncs : LOAD = FLASHD, RUN = RAML0, LOAD_START(_RamfuncsLoadStart), LOAD_END(_RamfuncsLoadEnd), RUN_START(_RamfuncsRunStart), PAGE = 0 ramfuncs2 : LOAD = FLASHB, /* 与RAMH0同属PAGE1区 */ RUN = RAMH0, LOAD_START(_RamfuncsLoadStart2), LOAD_END(_RamfuncsLoadEnd2), RUN_START(_RamfuncsRunStart2), PAGE = 1
改成上面的代码后会首先报错，找不到RamfuncsLoadStart2、_RamfuncsLoadEnd2和_RamfuncsRunStart2，仍采用复制的方法，首先找到_RamfuncsLoadStart定义的位置(DSP281x_GlobalPrototypes.h)，改后如下：
extern Uint16 RamfuncsLoadStart; extern Uint16 RamfuncsLoadEnd; extern Uint16 RamfuncsRunStart;
//以下为新增加 extern Uint16 RamfuncsLoadStart2; extern Uint16 RamfuncsLoadEnd2; extern Uint16 RamfuncsRunStart2;
定义好之后，就是在主程序中将程序从FLASH中copy到RAM的部分再复制一次，如：
InitSysCtrl();
MemCopy(&RamfuncsLoadStart, &RamfuncsLoadEnd, &RamfuncsRunStart);//将定义在ramfuncs段中的数据从FLASH拷贝到RAM中MemCopy(&RamfuncsLoadStart2, &RamfuncsLoadEnd2, &RamfuncsRunStart2);//将定义在ramfuncs2段中的数据从FLASH 拷贝到RAM中(新增加)
InitFlash();
经过以上更改后，就可以将子程序放到ramfuncs2中了，如下：#pragma CODE_SECTION(delay, “ramfuncs”); #pragma CODE_SECTION(delay3, “ramfuncs”); #pragma CODE_SECTION(SQRT_FPGA, “ramfuncs”);
#pragma CODE_SECTION(CTR_PRAM_CAL, “ramfuncs2”); //ramfuncs2为新增加数据段 #pragma CODE_SECTION(CTR_PRAM_CAL3, “ramfuncs2”); #pragma CODE_SECTION(CTR_PRAM_CAL4, “ramfuncs2”);
经过以上的两个步骤，可以充分利用DSP2812中总共18k RAM中的16k，剩下的2k可用于存储全局变量或者局部变量，完整的 cmd文件如下(可直接复制替换)：
MEMORY { PAGE 0: /* Program Memory / / Memory (RAM/FLASH/OTP) blocks can be moved to PAGE1 for data allocation */
ZONE0 : origin = 0x002000, length = 0x002000 /* XINTF zone 0 / ZONE1 : origin = 0x004000, length = 0x002000 / XINTF zone 1 / RAML0 : origin = 0x008000, length = 0x002000 / on-chip RAM block L0 / //0x001000 ZONE2 : origin = 0x080000, length = 0x080000 / XINTF zone 2 / ZONE6 : origin = 0x100000, length = 0x080000 / XINTF zone 6 / OTP : origin = 0x3D7800, length = 0x000800 / on-chip OTP / FLASHJ : origin = 0x3D8000, length = 0x002000 / on-chip FLASH / FLASHI : origin = 0x3DA000, length = 0x002000 / on-chip FLASH / FLASHH : origin = 0x3DC000, length = 0x004000 / on-chip FLASH / FLASHG : origin = 0x3E0000, length = 0x004000 / on-chip FLASH / FLASHF : origin = 0x3E4000, length = 0x004000 / on-chip FLASH / FLASHE : origin = 0x3E8000, length = 0x004000 / on-chip FLASH / FLASHD : origin = 0x3EC000, length = 0x004000 / on-chip FLASH / FLASHC : origin = 0x3F0000, length = 0x004000 / on-chip FLASH / FLASHA : origin = 0x3F6000, length = 0x001F80 / on-chip FLASH / CSM_RSVD : origin = 0x3F7F80, length = 0x000076 / Part of FLASHA. Program with all 0x0000 when CSM is in use. / BEGIN : origin = 0x3F7FF6, length = 0x000002 / Part of FLASHA. Used for “boot to Flash” bootloader mode. / CSM_PWL : origin = 0x3F7FF8, length = 0x000008 / Part of FLASHA. CSM password locations in FLASHA */
/* ZONE7 : origin = 0x3FC000, length = 0x003FC0 /* XINTF zone 7 available if MP/MCn=1 / ROM : origin = 0x3FF000, length = 0x000FC0 / Boot ROM available if MP/MCn=0 / RESET : origin = 0x3FFFC0, length = 0x000002 / part of boot ROM (MP/MCn=0) or XINTF zone 7 (MP/MCn=1) / VECTORS : origin = 0x3FFFC2, length = 0x00003E / part of boot ROM (MP/MCn=0) or XINTF zone 7 (MP/MCn=1) */
PAGE 1 : /* Data Memory / / Memory (RAM/FLASH/OTP) blocks can be moved to PAGE0 for program allocation / / Registers remain on PAGE1 */
RAMM0 : origin = 0x000000, length = 0x000400 /* on-chip RAM block M0 / RAMM1 : origin = 0x000400, length = 0x000400 / on-chip RAM block M1 / // RAML1 : origin = 0x00A000, length = 0x000000 / on-chip RAM block L1 / FLASHB : origin = 0x3F4000, length = 0x002000 / on-chip FLASH / RAMH0 : origin = 0x3F8000, length = 0x002000 / on-chip RAM block H0 */ }
/* Allocate sections to memory blocks. Note: codestart user defined section in DSP28_CodeStartBranch.asm used to redirect code execution when booting to flash ramfuncs user defined section to store functions that will be copied from Flash into RAM */
SECTIONS {
/* Allocate program areas: */ .cinit : > FLASHC PAGE = 0//FLASHA .pinit : > FLASHC, PAGE = 0//FLASHA .text : > FLASHC PAGE = 0//FLASHA codestart : > BEGIN PAGE = 0 ramfuncs : LOAD = FLASHD, RUN = RAML0, LOAD_START(_RamfuncsLoadStart), LOAD_END(_RamfuncsLoadEnd), RUN_START(_RamfuncsRunStart), PAGE = 0 ramfuncs2 : LOAD = FLASHB, RUN = RAMH0, LOAD_START(_RamfuncsLoadStart2), LOAD_END(_RamfuncsLoadEnd2), RUN_START(_RamfuncsRunStart2), PAGE = 1
csmpasswds : > CSM_PWL PAGE = 0 csm_rsvd : > CSM_RSVD PAGE = 0
/* Allocate uninitalized data sections: */ .stack : > RAMM0 PAGE = 1 .ebss : > RAMM1 PAGE = 1 .esysmem : > RAMM1 PAGE = 1
/* Initalized sections go in Flash / / For SDFlash to program these, they must be allocated to page 0 */ .econst : > FLASHC PAGE = 0 //FLASHA .switch : > FLASHC PAGE = 0 //FLASHA
/* Allocate IQ math areas: / IQmath : > FLASHA PAGE = 0 //FLASHC / Math Code / IQmathTables : > ROM PAGE = 0, TYPE = NOLOAD / Math Tables In ROM */
/* .reset is a standard section used by the compiler. It contains the / / the address of the start of _c_int00 for C Code. /* /* When using the boot ROM this section and the CPU vector / / table is not needed. Thus the default type is set here to / / DSECT */ .reset : > RESET, PAGE = 0, TYPE = DSECT vectors : > VECTORS PAGE = 0, TYPE = DSECT
}
经过以上改动后，新扩展的RAM区实测可用！ 一些理解：LOAD_START(_RamfuncsLoadStart)表示告诉编译器将这一段编译之后产生的起始地址存入RamfuncsLoadStart变量中，其他的变量也类似，这样在主程序运行时的MemCopy()才会找到相应的数值，也就是说LOAD_START(_RamfuncsLoadStart)这句是赋值功能。文章转载自：https://www.cnblogs.com/liwei-chengdu/p/9407358.html
