EETS4K 模块应用笔记（1）

9S12 系列单片机的通常包含4KB 的EEPROM。Freescale 将EEPROM 模块称之为 EETS4K。实际上，这里所谓的 EEPROM 其实是FLASH，只不过Freescale 特意将这里Flash 的 sector 做的很小（4Bytes），使得用户用起来像是在用 EEPROM。

EEPROM 是直接映射到9S12 单片机的地址空间的，如果程序中只是读取 EEPROM 中的内容，而不涉及到对 EEPROM 中数据的修改。那就不需要特殊的编程。就像读取RAM数据那样直接访问就可以了。

只有当需要在程序中更新EEPROM 中内容时，才需要学习下面的内容。

初始化EETS4K

在向EETS4K写入数据或擦除数据前要先配置EETS4K的时钟。EETS4K的时钟频率必须在150KHz——200KHz之间，为此需要配置 ECLKDIV 寄存器。

ECLKDIV 寄存器(EEPROM Clock Divider Register)

图 1ECLKDIV 寄存器

PRDIV8是预分频位：当PRDIV8=1时输入时钟被预分频为1/8。

EDIV5——EDIV8为分频除数寄存器，最多可以产生1/64 的分频比。简单的计算可知，当输入时钟大于12.8MHz 时需要将 PRDIV8 置位。

经过PRDIV8和EDIV两级分频最多可将时钟频率分为1/512。

擦除和写入和读取

这里不详细介绍每一个寄存器的用法。只对需要注意的地方加以说明。

EETS4K 模块的最小擦除单位是4Bytes，EETS4K 模块提供了两条相关命令，一条是擦除一个 sector，也就是 4 字节，并且要求是字节对其的双字。另一条命令擦除全部EEPROM 空间。

每次编程（写入）单位为两个字节。并且这两个字节要是对其字。

当EETS4K 模块正在进行擦除或编程操作时是不能同时读取EEPROM中内容的。

有了这些介绍就够了。下面给出一个具体的例子。

/*EETS4K.h*/
#ifndef NVM_H
#define NVM_H
/*
* CONSTANTS
*/
#define NVM_NO_ERR (1)
#define NVM_ODD_ACCESS_ERR (-1)
#define NVM_ACCESS_ERR (-2)
#define NVM_PROTECTION_ERR (-3)
/*
* FUNCTION PROTOTYPES
*/
void EEPROM_Init(unsigned long sysclk);
char EEPROM_Write_Word(unsigned int address, unsigned int data);
char EEPROM_Erase_Sector(unsigned int address);
char EEPROM_Erase_All (void);
unsigned int EEPROM_Read_Word(unsigned int address);
#endif /* End of file */

/*EETS4K.C*/
#include /* common defines and macros */
#include "derivative.h" /* derivative-specific definitions */
#include "eets4k.h"
/** @brief This function initializes the Non Volatile EEPROM control registers
* and must be called before attempting to write or erase an EEPROM sector.
*
* @para sysclk the CPU clock frequency (SYSCLK) driven by the onboard oscillator or the PLL if enabled.
*/
void EEPROM_Init (unsigned long sysclk)
{
unsigned char eclk_val;
if (sysclk >= 12000) { /* If the SYSCLK is > 12MHz, then set FDIV8 bit */
eclk_val = (sysclk / (8*200)) - 1; /* Compute the correct divider value */
ECLKDIV |= ECLKDIV_PRDIV8_MASK | eclk_val; /* Write the ECLKDIV register with the correct settings */
} else {
eclk_val = (sysclk / 200) - 1; /* Compute the correct divider value */
ECLKDIV |= eclk_val; /* Write the ECLKDIV register with the correct settings */
}
ESTAT |= (ESTAT_PVIOL_MASK | ESTAT_ACCERR_MASK); /* Clear any error flags */
}
/** @brief This function writes a 16-bit word to EEPROM
* @param address, the destination EEPROM address to write the data
* @param data, the data to write to argument address.
* @return
* NVM_NO_ERR - EEPROM Write Success
* NVM_ODD_ACCESS_ERR - EEPROM Write Error, Address not on an even address boundry
* NVM_ACCESS_ERR - EEPROM Write Error, Access Violation
* NVM_PROTECTION_ERR - EEPROM Write Error, Attempted to write a protected sector
*/
char EEPROM_Write_Word (unsigned int address, unsigned int data)
{
while (!ESTAT_CBEIF) { /* Wait for EEPROM access controller to become ready */
;
}
ESTAT = (ESTAT_ACCERR_MASK | ESTAT_PVIOL_MASK); /* Clear existing error flags */
if (address & 0x0001) {
return (NVM_ODD_ACCESS_ERR); /* Address is NOT aligned on an even boundry? */
}
(*(unsigned int *)address) = data; /* Write the data to the specified address */
ECMD = ECMD_CMDB5_MASK; /* Store programming command in FCMD */
ESTAT_CBEIF = 1; /* Execute the command */
if (ESTAT_ACCERR) { /* Check if there has been an access error */
return (NVM_ACCESS_ERR); /* Return an Access Error code */
}
if (ESTAT_PVIOL) { /* Check if there has been a protection error */
return (NVM_PROTECTION_ERR); /* Return a Protection Error code */
}
return (NVM_NO_ERR); /* Return No Error */
}
/** @brief This function erases a 4-byte sector of EEPROM
* @param address, the start of the 4-byte sector to address
* @return
* NVM_NO_ERR - EEPROM Write Success
* NVM_ODD_ACCESS_ERR - EEPROM Write Error, Address not on an even address boundry
* NVM_ACCESS_ERR - EEPROM Write Error, Access Violation
* NVM_PROTECTION_ERR - EEPROM Write Error, Attempted to write a protected sector
*/
char EEPROM_Erase_Sector (unsigned int address)
{
while (!ESTAT_CBEIF) { /* Wait for EEPROM access controller to become ready */
;
}
ESTAT = (ESTAT_ACCERR_MASK | ESTAT_PVIOL_MASK); /* Clear existing error flags */
if (address & 0x0001) {
return (NVM_ODD_ACCESS_ERR); /* Address is NOT aligned on an even boundry? */
}
(*(unsigned int *)address) = 0xFFFF; /* Write the data to the specified address */
ECMD = ECMD_CMDB6_MASK; /* Store programming command in FCMD */
ESTAT_CBEIF = 1; /* Execute the command */
if (ESTAT_ACCERR) { /* Check if there has been an access error */
return (NVM_ACCESS_ERR); /* Return an Access Error code */
}
if (ESTAT_PVIOL) { /* Check if there has been a protection error */
return (NVM_PROTECTION_ERR); /* Return a Protection Error code */
}
return (NVM_NO_ERR); /* Return No Error */
}
char EEPROM_Erase_All (void)
{
while (!ESTAT_CBEIF) { /* Wait for EEPROM access controller to become ready */
;
}
ESTAT = (ESTAT_ACCERR_MASK | ESTAT_PVIOL_MASK); /* Clear existing error flags */
(*(unsigned int *)0x0400) = 0xFFFF; /* Write the data to the specified address */
ECMD = 0x41; /* Store programming command in FCMD */
ESTAT_CBEIF = 1; /* Execute the command */
if (ESTAT_ACCERR) { /* Check if there has been an access error */
return (NVM_ACCESS_ERR); /* Return an Access Error code */
}
if (ESTAT_PVIOL) { /* Check if there has been a protection error */
return (NVM_PROTECTION_ERR); /* Return a Protection Error code */
}
return (NVM_NO_ERR); /* Return No Error */
}
/** @brief This function reads a 16-bit word from the specified address in EEPROM
* @param address, the start of the 16-bit data to read
* @return The 16-bit word stored in location 'address'
*/
unsigned int EEPROM_Read_Word (unsigned int address)
{
unsigned int data;
while (!ESTAT_CBEIF) { /* Wait for EEPROM access controller to become ready */
;
}
data = (*(unsigned int *)address); /* Read the data at location 'address' */
return (data); /* Return the data*/
}