SDRAM读取速度很慢

发布于 2024-09-05 21:52:37 浏览：177 订阅该版

stm32h750 运行频率400MHz，SDRAM 16bit 8MB，FMC时钟200MHz 二分频，使用rtthread带的sdram驱动，sdram读写速度测试，8MB写74ms，读240ms，cache不开启，读不做数据准确性判断，算下来写108MB/s，读33MB/s，看到网上32bit sdram都是写360MB左右，读180MB左右，按理16bit的应该有一半的速度吧，为何我的读取这么慢？

下面是sdram配置
```c
/* data width: 8, 16, 32 */
#define SDRAM_DATA_WIDTH                16
/* column bit numbers: 8, 9, 10, 11 */
#define SDRAM_COLUMN_BITS               8
/* row bit numbers: 11, 12, 13 */
#define SDRAM_ROW_BITS                  12
/* cas latency clock number: 1, 2, 3 */
#define SDRAM_CAS_LATENCY               3
/* read pipe delay: 0, 1, 2 */
#define SDRAM_RPIPE_DELAY               0
/* clock divid: 2, 3 */
#define SDCLOCK_PERIOD                  2
/* refresh rate counter */
#define SDRAM_REFRESH_COUNT             ((uint32_t)1543)
#define SDRAM_SIZE                      ((uint32_t)0x800000)  // W9825G6KH - 0x2000000, W9864G6KH - 0x800000,
	
#define LOADTOACTIVEDELAY               2
/* TXSR: 8x10ns */
#define EXITSELFREFRESHDELAY            8   //最小 72 ns, (120MHz)72/8.33 = 9, (100MHz)72/10 = 8
/* TRAS: 5x10ns */
#define SELFREFRESHTIME                 5   //最小 42 ns, (120MHz)42/8.33 = 6, (100MHz)42/10 = 5
/* TRC:  7x10ns */
#define ROWCYCLEDELAY                   6   //最小 60 ns, (120MHz)60/8.33 = 8, (100MHz)60/10 = 6
/* TWR:  2 Clock cycles */
#define WRITERECOVERYTIME               2   //最小 2 Tck
/* TRP:  2x10ns */
#define RPDELAY                         2   //最小 15 ns, 15/8.33 = 2
/* TRCD: 2x10ns */
#define RCDDELAY                        2   //最小 15 ns, 15/8.33 = 2	
	
	
```