DSP学习笔记----EMIF(外部存储器接口)
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.****.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