一. EMIF介绍
CE空间：
dsp的存储空间分为片内和片外两种，片外空间分成四个部分，分别用于映射不同的片外设备，即ce空间 。
The remainder of the memory map is external space that is divided into four spaces. Each space has a chip enable decode signal (called CE) that indicates an access to the selected space.
内存映射的其余部分是被划分为四个空间的外部空间。每个空间都有一个可芯片解码信号(称为CE)，表示对所选空间的访问。
EMIF就是外部存储器接口，知识DSP上的引脚，用于外接存储器设备。CPU与外部存储器的连接口。在芯片上的位置如下图。
它的结构框图如下：
接口位的作用及配置参考: https://blog.csdn.net/app_12062011/article/details/7869589
EMIF支持的存储器：
1 异步存储器，包括ROM,FLASH,异步SRAM
2 同步突发静态存储器（SBSRAM）
3 同步动态存储器（SDRAM）
二. EMIF设计
EMIF的设计要针对不同的存储器，C55x设置了4个片选信号CE0~CE3，直接作为外部存储器的选通信号。
三. EMIF编程实验
最重要的是配置寄存器
对于与SDRAM连接的配置过程：
配置开始->全局控制寄存器配置EMIF时钟->CE空间寄存器配置SDRAM空间->SDCTL配置SDRAM工作模式->SDTIM配置刷新模式->配置扩展功能->配置结束
(就是通过EMIF的寄存器去控制SDRAM的接口?)
总的程序
/******************************************************************************/ /******************************************************************************/ /*----------------------------------------------------------------------------*/ /* MODULE NAME... EMIF */ /* FILENAME...... emif.c */ /* DATE CREATED.. Wed 2/4/2004 */ /* PROJECT....... write and read data between the CPU and SDRAM */ /* COMPONENT..... */ /* PREREQUISITS.. */ /*----------------------------------------------------------------------------*/ /*----------------------------------------------------------------------------*/ /* DESCRIPTION: */ /* */ /* This is an example for EMIF of C5509 */ /*----------------------------------------------------------------------------*/ #include <csl.h> #include <csl_pll.h> #include <csl_emif.h> #include <csl_chip.h> #include <stdio.h> Uint16 x; Uint32 y; CSLBool b; unsigned int datacount = 0; int databuffer[1000] ={0}; int *souraddr,*deminaddr; /*锁相环的设置*/ PLL_Config myConfig = { 0, //IAI: the PLL locks using the same process that was underway //before the idle mode was entered 1, //IOB: If the PLL indicates a break in the phase lock, //it switches to its bypass mode and restarts the PLL phase-locking //sequence 20, //PLL multiply value; multiply 24 times 1 //Divide by 2 PLL divide value; it can be either PLL divide value //(when PLL is enabled), or Bypass-mode divide value //(PLL in bypass mode, if PLL multiply value is set to 1) }; /*SDRAM的EMIF设置*/ EMIF_Config emiffig = { 0x221, //EGCR : the MEMFREQ = 00,the clock for the memory is equal to cpu frequence // the WPE = 0 ,forbiden the writing posting when we debug the EMIF // the MEMCEN = 1,the memory clock is reflected on the CLKMEM pin // the NOHOLD = 1,HOLD requests are not recognized by the EMIF 0xFFFF, //EMI_RST: any write to this register resets the EMIF state machine 0x3FFF, //CE0_1: CE0 space control register 1 // MTYPE = 011,Synchronous DRAM(SDRAM),16-bit data bus width 0xFFFF, //CE0_2: CE0 space control register 2 0x00FF, //CE0_3: CE0 space control register 3 // TIMEOUT = 0xFF; 0x7FFF, //CE1_1: CE0 space control register 1 0xFFFF, //CE1_2: CE0 space control register 2 0x00FF, //CE1_3: CE0 space control register 3 0x7FFF, //CE2_1: CE0 space control register 1 0xFFFF, //CE2_2: CE0 space control register 2 0x00FF, //CE2_3: CE0 space control register 3 0x7FFF, //CE3_1: CE0 space control register 1 0xFFFF, //CE3_2: CE0 space control register 2 0x00FF, //CE3_3: CE0 space control register 3 0x2911, //SDC1: SDRAM control register 1 // TRC = 8 // SDSIZE = 0;SDWID = 0 // RFEN = 1 // TRCD = 2 // TRP = 2 0x0410, //SDPER : SDRAM period register // 7ns *4096 0x07FF, //SDINIT: SDRAM initialization register // any write to this register to init the all CE spaces, // do it after hardware reset or power up the C55x device 0x0131 //SDC2: SDRAM control register 2 // SDACC = 0; // TMRD = 01; // TRAS = 0101; // TACTV2ACTV = 0001; }; main() { unsigned int error=0; /*初始化CSL库*/ CSL_init(); /*EMIF为全EMIF接口*/ CHIP_RSET(XBSR,0x0a01); /*设置系统的运行速度为120MHz*/ PLL_config(&myConfig); /*初始化DSP的外部SDRAM*/ EMIF_config(&emiffig); /*向SDRAM中写入数据*/ souraddr = (int *)0x40000; deminaddr = (int *)0x41000; while(souraddr<deminaddr) { *souraddr++ = datacount; //address : 40000-41000 write in : 0-1000 datacount++ ; } /*读出SDRAM中的数据*/ souraddr = (int *)0x40000; datacount = 0; while(souraddr<deminaddr) { databuffer[datacount++] = *souraddr++; printf("%d\n",databuffer[datacount-1]); if(databuffer[datacount-1]!=(datacount-1)) error++; //printf("%d",datacount-1); } if(error==0) { printf("SDRAM test completed! No Error!"); } while(1); } /******************************************************************************\ * End of pll2.c \******************************************************************************/四.参考博客
https://blog.csdn.net/app_12062011/article/details/7869589
