我用的芯片是LPC2468，SDRAM是K4S561632H,在调试EMC模块（SDRAM）的时候碰到下面的问题，请教周工及高手帮忙
EMC_DYN_RP = 2; /* command period: 3(n+1) clock cycles */
EMC_DYN_RAS = 3; /* RAS command period: 4(n+1) clock cycles */
EMC_DYN_SREX = 7; /* Self-refresh period: 8(n+1) clock cycles */
EMC_DYN_APR = 2; /* Data out to active: 3(n+1) clock cycles */
EMC_DYN_DAL = 5; /* Data in to active: 5(n+1) clock cycles */
EMC_DYN_WR = 1; /* Write recovery: 2(n+1) clock cycles */
EMC_DYN_RC = 5; /* Active to Active cmd: 6(n+1) clock cycles */
EMC_DYN_RFC = 5; /* Auto-refresh: 6(n+1) clock cycles */
EMC_DYN_XSR = 7; /* Exit self-refresh: 8(n+1) clock cycles */
EMC_DYN_RRD = 1; /* Active bank A->B: 2(n+1) clock cycles */
EMC_DYN_MRD = 2; /* Load Mode to Active cmd: 3(n+1) clock cycles */
EMC_DYN_RD_CFG = 1; /* Command delayed strategy */
/* Default setting, RAS latency 3 CCLKs, CAS latenty 3 CCLKs. */
EMC_DYN_RASCAS0 = 0x00000303;
//#if ENG_BOARD_LPC24XX /* NXP engineering board */
/* 256MB, 16Mx16, 4 banks, row=12, column=9 */
//EMC_DYN_CFG0 = 0x00000480;
//#else /* Embedded Artists board */
/* 256MB, 16Mx16, 4 banks, row=13, column=9 */
EMC_DYN_CFG0 = 0x00000680;
//#endif
delayMs(1, 100); /* use timer 1 */
/* Mem clock enable, CLKOUT runs, send command: NOP */
EMC_DYN_CTRL = 0x00000183;
delayMs(1, 200); /* use timer 1 */
/* Send command: PRECHARGE-ALL, shortest possible refresh period */
EMC_DYN_CTRL = 0x00000103;
/* set 32 CCLKs between SDRAM refresh cycles */
EMC_DYN_RFSH = 0x00000002;
for(i = 0; i < 0x40; i++); /* wait 128 AHB clock cycles */
/* set 28 x 16CCLKs=448CCLK=7us between SDRAM refresh cycles */
EMC_DYN_RFSH = 28;
/* To set mode register in SDRAM, enter mode by issue
MODE command, after finishing, bailout and back to NORMAL mode. */
/* Mem clock enable, CLKOUT runs, send command: MODE */
EMC_DYN_CTRL = 0x00000083;
/* Set mode register in SDRAM */
/* Mode regitster table for Micron's MT48LCxx */
/* bit 9: Programmed burst length(0)
bit 8~7: Normal mode(0)
bit 6~4: CAS latency 3
bit 3: Sequential(0)
bit 2~0: Burst length is 8
row position is 12 */
dummy = *((volatile DWORD *)(SDRAM_BASE_ADDR | (0x33 << 12)));
EMC_DYN_CTRL = 0x00000000; /* Send command: NORMAL */
EMC_DYN_CFG0 |= 0x00080000; /* Enable buffer */
delayMs(1, 1); /* Use timer 1 */
return;
}
1。请问一下这条指令是为了实现什么功能？dummy = *((volatile DWORD *)(SDRAM_BASE_ADDR | (0x33 << 12)));
2。为何要写四个EMC_DYN_CTRL（红色部分）？一定要这样的顺序写吗？
3。我现在遇到了个问题，比如我第一次存入256个字节（1到256的数）到SDRAM，显示结果没问题，之后重新上电，看到SDRAM为全0，第二次写入10个字节(全为0)到SDRAM，显示结果确是低10个字节是全0，但是从第10个字节之后的数确是我第一次存入的那些数（两次存的起始地址是一样）怎么会这样？ |
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