freescale飞思卡尔 HC9S12 系列单片机 Flash擦写详解（三）之Flash控制器指令执行

　　前面我们介绍了Flash主要的几个寄存器，如果还有其他的疑问可以再返回去看看或者直接查阅S12系列单片机的手册中相关的内容。这一节我将介绍Flash控制器指令执行的过程，并举出相关的例子，希望能够起到举一反三的效果。

　　在手册中FCCOB寄存器下面，介绍了Flash寄存器执行指令的过程是这样的：

　　我们解释下：NVM执行指令时将通过FCCOB寄存器向存储控制器提供一个指令码还有其相关的参数，也就是说先根据指令码对FCCOB寄存器进行设置，然后通过对FSTAT寄存器中的CCIF位写入1从而使Flash控制器开始执行FCCOB中的指令（当向CCIF写1后，读取CCIF时其值将为0）。当用户向CCIF中写1后，FCCOB指令寄存器内的内容将被锁定直到此次指令执行结束。如果该指令码有返回值，则返回信息将会在FCCOB寄存器内。

　　我们稍微总结下Flash寄存器执行指令的过程：

　　1. 先通过调整FCCOBIX寄存器向FCCOB寄存器各个word中写入指令码与相关的参数

　　2. 向FSTAT的CCIF位中写入1，开始指令执行

　　3. 读取CCIF的值直到指令执行结束，若指令码有返回值则读取并返回（还有FSTAT中的其他位可能表示了写入过程中的错误信息）

　　这样就可以让Flashi控制器完成一次指令的执行了。下面我们看一下一个手册中的典型FCCOB寄存器的用法：

　　在上面的典型用法表中我们可以看到向Flash中写入8个Byte的过程应该如下方程序所示:

unsigned long address  = 0x020000 //将要在Flash中写入的数据首地址(全局地址)
unsigned int *ptr  = data     // word长度的数据指针
byte i

// 读取CCIF的值来判断Flash
while ((FSTAT & FSTAT_CCIF_MASK) == 0);
    
    
// 按照格式要求选择0x00
FCCOBIX = 0x00; // choose the 000 FCCOB
    
    /* 000 FCCOB  HI is 8 bits commands and LO is physical address Highest byte*/
    /* command 0x06 means program flash */
    /* warning: before program, the area must be erased*/
FCCOB = 0x0600 | ((address & 0x00030000) >> 16);
    
FCCOBIX = 0x01; //choose the 001 FCCOB
/* 001 FCCOB is the least 16bits physical address*/
 FCCOB = (address & 0x0000FFFF);
    
/* 0x02 - 0x05 FCCOB are 4x2 bytes write data*/
for (i = 2; i < 6; i++)
{
      FCCOBIX = i;
      FCCOB = *ptr; /* 2 bytes data each FCCOB */
      ptr ++; /* next 2 bytes */
}
  
FSTAT = 0x80; /* set CCIF to clear CCIF and launch command */
while ((FSTAT & FSTAT_CCIF_MASK) == 0); /* wait command done */
    

　　请仔细阅读上方的代码，在代码中我使用了向Flash中写入8个Byte的指令码0x06，完成的效果就是将上方表格所示的FCCOB中的内容设置满，然后启动并执行指令，直到指令被完全执行成功。

　　这里有四点需要强调，

　　首先是不同的指令码对应着FCCOB中不同的内容要求，具体设置情况根据需要，参照手册中对每个指令码的要求来编写。

　　其次是Flash的操作地址模式为全局地址，也就是上面表格中Global address，先把全局地址与分页地址的关系搞清楚了再做Flash的操作。

　　第三是Flash的擦写程序必须要复制到RAM中执行才可以执行，复制代码到RAM中执行前要在prm文件中使用RELOCATE_TO关键词，将代码拷贝至内存中运行（在bootloader详解教程中有写如何将ROM中的代码拷贝至RAM中），这是因为Flash的操作不能读写同步的，当Flash控制器在执行指令时，单片机无法从Flash读出指令，一定要先将Flash擦写的代码拷贝至RAM中运行才可以。

　　第四是，在写入Flash之前，务必要确定该片Flash区域已经被擦除了，否则会出现写入错误。

　　后面我还会展示一点代码，对于初学者，将下面的代码每一句都弄懂，对照着器件手册理解了，基本上Flash这部分内容就算是勉强出师了。其间涉及到了错误信息的处理，在手册里查一查都有的。

　　还想说一下本人写这个教程的初衷，因为首先自己搞的时候确实很头大，这样把过程写出来十分畅快，其次就是在下目前在下的环境，完全不参与什么行业竞争，这些只是需要读一读器件手册就能完成的事情，发出来对大家有用就好。下面贴代码，代码包括prm文件设置，Flash擦写头文件与实现，还有个将ROM中程序复制到RAM中运行的程序。要是根据我这个教程将Flash调通的，在教程下评论下吧，并不是要推荐，只是想看看帮到了多少人。

prm文件设置

NAMES END

SEGMENTS 
/* Register space  */
/*    IO_SEG        = PAGED         0x0000 TO   0x03FF; intentionally not defined */

/* RAM */
      RAM           = READ_WRITE    0x2000 TO   0x3BFF;
      CODE_RAM      = READ_WRITE    0x3C00 TO   0x3FFF; /*1 kB for flash read and write*/

/* D-Flash */
      DFLASH        = READ_ONLY   0x000400 TO 0x0013FF;

/* non-paged FLASHs */
      ROM_1400      = READ_ONLY     0x1400 TO   0x1FFF;
      
      ROM_BOOT      = READ_ONLY     0x4000 TO   0x43FF;   // 1KB for boot loader
      ROM_FLASH     = READ_ONLY     0X4400 TO   0x47FF RELOCATE_TO 0x3C00;  // 1KB for necessary flash operation 
      
      ROM_C000      = READ_ONLY     0xC000 TO   0xFEFF; 
 /*   VECTORS       = READ_ONLY     0xFF00 TO   0xFFFF; intentionally not defined: used for VECTOR commands below */
   //OSVECTORS      = READ_ONLY     0xFF80 TO   0xFFFF;   /* OSEK interrupt vectors (use your vector.o) */

/* paged FLASH:                     0x8000 TO   0xBFFF; addressed through PPAGE */
      PAGE_08       = READ_ONLY   0x088000 TO 0x08BFFF;
      PAGE_09       = READ_ONLY   0x098000 TO 0x09BFFF;
      PAGE_0A       = READ_ONLY   0x0A8000 TO 0x0ABFFF;
      PAGE_0B       = READ_ONLY   0x0B8000 TO 0x0BBFFF;
      PAGE_0C       = READ_ONLY   0x0C8000 TO 0x0C93FF;
      PAGE_0C_A000  = READ_ONLY   0x0CA000 TO 0x0CBFFF;
      PAGE_0E       = READ_ONLY   0x0E8000 TO 0x0EBFFF;
/*    PAGE_0D       = READ_ONLY   0x0D8000 TO 0x0DBFFF; not used: equivalent to ROM_4000 */
/*    PAGE_0F       = READ_ONLY   0x0F8000 TO 0x0FBEFF; not used: equivalent to ROM_C000 */
END

PLACEMENT /* here all predefined and user segments are placed into the SEGMENTS defined above. */
      _PRESTART,              /* Used in HIWARE format: jump to _Startup at the code start */
      STARTUP,                /* startup data structures */
      ROM_VAR,                /* constant variables */
      STRINGS,                /* string literals */
      VIRTUAL_TABLE_SEGMENT,  /* C++ virtual table segment */
    //.ostext,                /* OSEK */
      NON_BANKED,             /* runtime routines which must not be banked */
      COPY                    /* copy down information: how to initialize variables */
                              /* in case you want to use ROM_4000 here as well, make sure
                                 that all files (incl. library files) are compiled with the
                                 option: -OnB=b */
                        INTO  ROM_C000/*, ROM_1400, ROM_4000*/;
                        
      BOOTLOADER        INTO  ROM_BOOT;
      FLASH_CODE        INTO  ROM_FLASH;
                        
      
      USER_APP          INTO  PAGE_08;
      TEST_AREA         INTO  PAGE_09;  /* physical address from 0x2_4000 */
      DEFAULT_ROM       INTO  PAGE_0A, PAGE_0B, PAGE_0C, PAGE_0C_A000, PAGE_0E                  ;

    //.stackstart,            /* eventually used for OSEK kernel awareness: Main-Stack Start */
      SSTACK,                 /* allocate stack first to avoid overwriting variables on overflow */
    //.stackend,              /* eventually used for OSEK kernel awareness: Main-Stack End */
    DEFAULT_RAM         INTO  RAM;

  //.vectors            INTO  OSVECTORS; /* OSEK */
END

ENTRIES /* keep the following unreferenced variables */
    /* OSEK: always allocate the vector table and all dependent objects */
  //_vectab OsBuildNumber _OsOrtiStackStart _OsOrtiStart
END

STACKSIZE 0x100

VECTOR 0 _Startup /* reset vector: this is the default entry point for a C/C++ application. */
//VECTOR 0 Entry  /* reset vector: this is the default entry point for an Assembly application. */
//INIT Entry      /* for assembly applications: that this is as well the initialization entry point */

VECTOR ADDRESS 0xFFD6 SCI0_INT_receive

Flash擦写头文件

#ifndef  _FLASH_LIB_H
#define  _FLASH_LIB_H

#include <mc9s12g128.h>

typedef enum
{
    NoError           = 0,
    FlashProgramError = 1,
    FlashEraseError   = 2
} FlashMsg;

#pragma CODE_SEG  BOOTLOASER

void Init_Flash(void);

#pragma CODE_SEG  DEFAULT

#pragma CODE_SEG FLASH_CODE

FlashMsg Flash_Program(unsigned long address, unsigned int *ptr);

FlashMsg Flash_EraseSector(unsigned long address);


#pragma CODE_SEG DEFAULT

#endif

Flash擦写实现

#include "FLASH_LIB.h"

/* a sector contains 512 bytes */
#define FLASH_SECTOR_SIZE  0x200 
 

#pragma CODE_SEG  BOOTLOASER

void Init_Flash(void)
{
    // bus clock is  8MHz
    // read the manual reference get the respective value
    
    // check if the flash controller is busy or not
    while ((FSTAT & FSTAT_CCIF_MASK) == 0);
    
    // set the clock divider according to bus clock
    FCLKDIV = 0x07;
    
    // lock the divider
    FCLKDIV_FDIVLCK = 1;
     
}

#pragma CODE_SEG  DEFAULT


#pragma CODE_SEG FLASH_CODE

FlashMsg Flash_Program(unsigned long address, unsigned int *ptr)
{
    byte i;
    
    /*CCIF is the 7th bit of FSTAT
      CCIF is 0, the flash controller is busy
      wait until CCIF become 1*/
    while ((FSTAT & FSTAT_CCIF_MASK) == 0);
    
    /*clear ACCERR (flash access error) 5th bit
      clear PVIOL (protection violation error)  4th bit
      , or the CCIF cannot be cleared*/
    FSTAT = 0x30;
    
    /*write flash command, operation address and input parameters*/
    FCCOBIX = 0x00; // choose the 000 FCCOB
    
    /* 000 FCCOB  HI is 8 bits commands and LO is physical address Highest byte*/
    /* command 0x06 means program flash */
    /* warning: before program, the area must be erased*/
    FCCOB = 0x0600 | ((address & 0x00030000) >> 16);
    
    FCCOBIX = 0x01; //choose the 001 FCCOB
    /* 001 FCCOB is the least 16bits physical address*/
    FCCOB = (address & 0x0000FFFF);
    
    /* 0x02 - 0x05 FCCOB are 4x2 bytes write data*/
    for (i = 2; i < 6; i++)
    {
        FCCOBIX = i;
        FCCOB = *ptr; /* 2 bytes data each FCCOB */
        ptr ++; /* next 2 bytes */
    }
    
    FSTAT = 0x80; /* set CCIF to clear CCIF and launch command */
    while ((FSTAT & FSTAT_CCIF_MASK) == 0); /* wait command done */
    
    /*read the error flag and return error message*/
    if ((FSTAT & (FSTAT_ACCERR_MASK | FSTAT_FPVIOL_MASK)) != 0)
        return FlashProgramError;
    else
        return NoError;  
        
}

FlashMsg Flash_EraseSector(unsigned long address)
{
    while ((FSTAT & FSTAT_CCIF_MASK) == 0);
    FSTAT = 0x30;
    
    /* command 0x0A means erased all address in the sector*/
    FCCOBIX = 0x00;
    FCCOB = 0x0A00 | ((address & 0x00030000) >> 16); 
    
    FCCOBIX = 0x01;
    FCCOB = (address & 0x0000FFF8); /*get the sector*/
    
    FSTAT = 0x80; /* launch command*/
    while ((FSTAT & FSTAT_CCIF_MASK) == 0); /*wait for done*/

    if ((FSTAT & (FSTAT_ACCERR_MASK | FSTAT_FPVIOL_MASK | 
                  FSTAT_MGSTAT_MASK)) != 0)
        return FlashEraseError;
    else
        return NoError;
}


#pragma CODE_SEG DEFAULT

ROM中内容复制到RAM中函数

void MoveCodeIntoRam(byte *source, byte *dest, unsigned int size)
{
    while (size --)
    {
        *dest ++ = *source ++;
    }
}

对应本prm文件调用复制函数

MoveCodeIntoRam((byte *)0x4400, (byte *)0x3C00, 0x400);

 

 本节内容小结：

　　1. 通过实例展示了S12系列单片机通过Flash指令寄存器让Flash控制器执行操作的过程

　　2. 给出了在擦写Flash的四个重要问题

　　3. 给出了可以调用的实例程序

 

注： 本系列文章均为原创，如有转载引用请标明来源