关于STM32存储器的疑问【悬赏问答】

honestapple 提问时间：2012-8-16 21:16 /

有没有大侠能够解释一下为什么STM32F0给每个外设分配了那么大的空间。
例如：SPI2编址范围：0x4000 3800 - 0x4000 3BFF
可是根据定义
typedef struct
{
__IO uint16_t CR1; /*!< SPI Control register 1 (not used in I2S mode), Address offset: 0x00 */
uint16_t RESERVED0; /*!< Reserved, 0x02 */
__IO uint16_t CR2; /*!< SPI Control register 2, Address offset: 0x04 */
uint16_t RESERVED1; /*!< Reserved, 0x06 */
__IO uint16_t SR; /*!< SPI Status register, Address offset: 0x08 */
uint16_t RESERVED2; /*!< Reserved, 0x0A */
__IO uint16_t DR; /*!< SPI data register, Address offset: 0x0C */
uint16_t RESERVED3; /*!< Reserved, 0x0E */
__IO uint16_t CRCPR; /*!< SPI CRC polynomial register (not used in I2S mode), Address offset: 0x10 */
uint16_t RESERVED4; /*!< Reserved, 0x12 */
__IO uint16_t RXCRCR; /*!< SPI Rx CRC register (not used in I2S mode), Address offset: 0x14 */
uint16_t RESERVED5; /*!< Reserved, 0x16 */
__IO uint16_t TXCRCR; /*!< SPI Tx CRC register (not used in I2S mode), Address offset: 0x18 */
uint16_t RESERVED6; /*!< Reserved, 0x1A */
__IO uint16_t I2SCFGR; /*!< SPI_I2S configuration register, Address offset: 0x1C */
uint16_t RESERVED7; /*!< Reserved, 0x1E */
__IO uint16_t I2SPR; /*!< SPI_I2S prescaler register, Address offset: 0x20 */
uint16_t RESERVED8; /*!< Reserved, 0x22 */
} SPI_TypeDef;

SPI2寄存器的实际寻址空间为：0x4000 3800 - 0x4000 3822（其中还有好多保留的）。那么剩下的空间都用来干嘛？