发现f407中自带的初始化外部ram函数有问题，gpio没有设置为上拉，而且fsmc使用的不是bank1第三个区，我改成了范例形式，大家一起讨论一下可不可以，多提意见
void SystemInit_ExtMemCtl(void)
{
/*-- GPIOs Configuration -----------------------------------------------------*/
/*
+-------------------+--------------------+------------------+--------------+
+                       SRAM pins assignment                               +
+-------------------+--------------------+------------------+--------------+
| PD0  <-> FMC_D2  | PE0  <-> FMC_NBL0 | PF0  <-> FMC_A0 | PG0 <-> FMC_A10 |
| PD1  <-> FMC_D3  | PE1  <-> FMC_NBL1 | PF1  <-> FMC_A1 | PG1 <-> FMC_A11 |
| PD4  <-> FMC_NOE | PE3  <-> FMC_A19  | PF2  <-> FMC_A2 | PG2 <-> FMC_A12 |
| PD5  <-> FMC_NWE | PE4  <-> FMC_A20  | PF3  <-> FMC_A3 | PG3 <-> FMC_A13 |
| PD8  <-> FMC_D13 | PE7  <-> FMC_D4   | PF4  <-> FMC_A4 | PG4 <-> FMC_A14 |
| PD9  <-> FMC_D14 | PE8  <-> FMC_D5   | PF5  <-> FMC_A5 | PG5 <-> FMC_A15 |
| PD10 <-> FMC_D15 | PE9  <-> FMC_D6   | PF12 <-> FMC_A6 | PG9 <-> FMC_NE2 |
| PD11 <-> FMC_A16 | PE10 <-> FMC_D7   | PF13 <-> FMC_A7 |-----------------+
| PD12 <-> FMC_A17 | PE11 <-> FMC_D8   | PF14 <-> FMC_A8 |
| PD13 <-> FMC_A18 | PE12 <-> FMC_D9   | PF15 <-> FMC_A9 |
| PD14 <-> FMC_D0  | PE13 <-> FMC_D10  |-----------------+
| PD15 <-> FMC_D1  | PE14 <-> FMC_D11  |
|                  | PE15 <-> FMC_D12  |
+------------------+------------------+
*/
   /* Enable GPIOD, GPIOE, GPIOF and GPIOG interface clock */
  RCC->AHB1ENR   |= 0x00000078;
  
  /* Connect PDx pins to FMC Alternate function */
  GPIOD->AFR[0]  = 0x00cc00cc;
  GPIOD->AFR[1]  = 0xcccccccc;
  /* Configure PDx pins in Alternate function mode */  
  GPIOD->MODER   = 0xaaaa0a0a;
  /* Configure PDx pins speed to 100 MHz */  
  GPIOD->OSPEEDR = 0xffff0f0f;
  /* Configure PDx pins Output type to push-pull */  
  GPIOD->OTYPER  = 0x00000000;
  /* No pull-up, pull-down for PDx pins */
GPIOD->PUPDR   = 0x55550505;
/* Connect PEx pins to FMC Alternate function */
  GPIOE->AFR[0]  = 0xc00000cc;
  GPIOE->AFR[1]  = 0xcccccccc;
  /* Configure PEx pins in Alternate function mode */
  GPIOE->MODER   = 0xaaaa800a;
  /* Configure PEx pins speed to 100 MHz */
  GPIOE->OSPEEDR = 0xffffc00f;
  /* Configure PEx pins Output type to push-pull */  
  GPIOE->OTYPER  = 0x00000000;
  /* No pull-up, pull-down for PEx pins */
  GPIOE->PUPDR   = 0x55554005;
  /* Connect PFx pins to FMC Alternate function */
  GPIOF->AFR[0]  = 0x00cccccc;
  GPIOF->AFR[1]  = 0xcccc0000;
  /* Configure PFx pins in Alternate function mode */   
  GPIOF->MODER   = 0xaa000aaa;
  /* Configure PFx pins speed to 100 MHz */
  GPIOF->OSPEEDR = 0xff000fff;
  /* Configure PFx pins Output type to push-pull */  
  GPIOF->OTYPER  = 0x00000000;
  /* No pull-up, pull-down for PFx pins */
  GPIOF->PUPDR   = 0x55000555;
  /* Connect PGx pins to FMC Alternate function */
  GPIOG->AFR[0]  = 0x00cccccc;
  GPIOG->AFR[1]  = 0x000000c0;
  /* Configure PGx pins in Alternate function mode */
  GPIOG->MODER   = 0x00080aaa;
  /* Configure PGx pins speed to 100 MHz */
  GPIOG->OSPEEDR = 0x000c0fff;
  /* Configure PGx pins Output type to push-pull */  
  GPIOG->OTYPER  = 0x00000000;
  /* No pull-up, pull-down for PGx pins */
  GPIOG->PUPDR   = 0x00040555;
  
/*-- FMC Configuration ------------------------------------------------------*/
  /* Enable the FMC/FSMC interface clock */
  RCC->AHB3ENR         |= 0x00000001;
  
FSMC_Bank1->BTCR[4]=0X00000000;
FSMC_Bank1->BTCR[5]=0X00000000;
FSMC_Bank1E->BWTR[4]=0X00000000;
//操作BCR寄存器 使用异步模式,模式A(读写共用一个时序寄存器)
//BTCR[偶数]:BCR寄存器;BTCR[奇数]:BTR寄存器
FSMC_Bank1->BTCR[4]|=1<<12;//存储器写使能
FSMC_Bank1->BTCR[4]|=1<<4; //存储器数据宽度为16bit      
//操作BTR寄存器   （HCLK=168M, 1个HCLK=6ns      
FSMC_Bank1->BTCR[5]|=8<<8; //数据保持时间（DATAST）为9个HCLK 6*9=54ns   
FSMC_Bank1->BTCR[5]|=0<<4; //地址保持时间（ADDHLD）未用到     
FSMC_Bank1->BTCR[5]|=0<<0; //地址建立时间（ADDSET）为0个HCLK 0ns   
//闪存写时序寄存器  
FSMC_Bank1E->BWTR[4]=0x0FFFFFFF;//默认值
//使能BANK1区域3
FSMC_Bank1->BTCR[4]|=1<<0;  
//#if defined (STM32F40_41xxx)
//  /* Configure and enable Bank1_SRAM2 */
//  FSMC_Bank1->BTCR[2]  = 0x00001011;
//  FSMC_Bank1->BTCR[3]  = 0x00000201;
//  FSMC_Bank1E->BWTR[2] = 0x0fffffff;
//#endif  /* STM32F40_41xxx */
}
#endif /* DATA_IN_ExtSRAM */