mx51调试笔记（三）之sdram的初始化

   今天继续调试mx51板子，观察得到片内rom代码执行时未初始化内存sdram模块，故我在jlink里面初始化sdram模块，具体实现是。
   根据data sheet给出的实例代码：
  setmem ESDCTL0 = 0x83220000  // ESDCTL0: Enable controller
// Init DRAM on CS0
setmem ESDSCR = 0x04008008  // ESDSCR: Precharge command
setmem ESDSCR= 0x00008010  // ESDSCR: Refresh command
setmem ESDSCR= 0x00008010  // ESDSCR: Refresh command
setmem ESDSCR= 0x00338018  // ESDSCR: LMR with CAS=3 and BL=3 (Burst Length = 8)
setmem ESDSCR= 0x0020801a  // ESDSCR: EMR with half Drive strength
setmem ESDCTL0 = 0xC3220000  // ESDCTL0: 14 ROW, 10 COL, 32Bit, SREF=8
// ESDCFG0: tRFC:22clks, tXSR:28clks, tXP:2clks, tWTR:2clk, tRP:3clks, tMRD:2clks
//          tRAS:8clks, tRRD:2clks, tWR:3clks, tRCD:3clks, tRC:11clks
setmem ESDCFG0 = 0xC33574AA
setmem ESDMISC = 0x000a1700  // ESDMISC: AP=10, Bank interleaving on, MIF3 en, RALAT=2
setmem ESDCTL1 = 0x83220000  // ESDCTL1: Enable controller
//// Init DRAM on CS1
setmem ESDSCR = 0x0400800c  // ESDSCR: Precharge command
setmem ESDSCR= 0x00008014  // ESDSCR: Refresh command
setmem ESDSCR = 0x00008014  // ESDSCR: Refresh command
setmem ESDSCR = 0x0033801c  // ESDSCR: LMR with CAS=3 and BL=3 (Burst Length = 8)
setmem ESDSCR = 0x0020801e  // ESDSCR: EMR with half Drive strength
setmem ESDCTL1= 0xC3220000  // ESDCTL1: 14 ROW, 10 COL, 32Bit, SREF=8
//// ESDCFG1: tRFC:21clks, tXSR:28clks, tXP:2clks, tWTR:2clk, tRP:3clks, tMRD:2clks
////          tRAS:8clks, tRRD:2clks, tWR:3clks, tRCD:3clks, tRC:11clks
setmem ESDCFG1 = 0xC33574AA
setmem ESDSCR = 0x00000000 // ESDSCR - clear "configuration request" bit
  在jlink里面实现上面的操作命令如下：
  w4 0x83fd9000,0x83220000
w4 0x83fd9014,0x04008008
w4 0x83fd9014,0x00008010
w4 0x83fd9014,0x00008010
w4 0x83fd9014,0x00338018
w4 0x83fd9014,0x0020801a
w4 0x83fd9000,0xc3230000
w4 0x83fd9004,0xc33574aa
w4 0x83fd9010,0x000a1700
w4 0x83fd9014,0x0

   在linux下的汇编代码为：

#sdram_init.S
.global _start

_start:
        ldr r0,=0x83fd9000              //ESDCTL0: Enable controller
        ldr r1,=0x83220000
        str r0,[r1]

        ldr r0,=0x83fd9014              //ESDSCR: Precharge command
        ldr r1,=0x04008008
        str r0,[r1]

        ldr r0,=0x83fd9014              //ESDSCR: Refresh command
        ldr r1,=0x00008010
        str r0,[r1]

        ldr r0,=0x83fd9014              // ESDSCR: Refresh command
        ldr r1,=0x00008010
        str r0,[r1]

        ldr r0,=0x83fd9014              //ESDSCR: LMR with CAS=3 and BL=3 (Burst Length = 8)
        ldr r1,=0x00338018
        str r0,[r1]

        ldr r0,=0x83fd9014              //ESDSCR: EMR with half Drive strength
        ldr r1,=0x0020801a
        str r0,[r1]

        ldr r0,=0x83fd9000              // ESDCTL0: 14 ROW, 10 COL, 32Bit, SREF=8 ESDCFG0: tRFC:22clks, tXSR:28clks, tXP:2clks, tWTR:2clk, tRP:3clks, tMRD:2clks tRAS:8clks, tRRD:2clks, tWR:3clks, tRCD:3clks, tRC:11clks
        ldr r1,=0xc3230000     
        str r0,[r1]

        ldr r0,=0x83fd9004
        ldr r1,=0xc33574aa
        str r0,[r1]

        ldr r0,=0x83fd9010              // ESDMISC: AP=10, Bank interleaving on, MIF3 en, RALAT=2
        ldr r1,=0x000a1700
        str r0,[r1]

        ldr r0,=0x83fd9014
        ldr r1,=0x0
        str r0,[r1]

  编译成boot.bin文件，命令：

   arm-linux-gcc -c sdram_init.S

   arm-linux-ld -Ttext 0x90000000 sdram_init.o -Map boot.map -o boot.elf

   arm-linux-objcopy -O binary boot.elf boot.bin

 此后，sdram可以读写了。然后通过loadbin命令加载可执行的bin文件到sdram空间执行即可：loadbin u-boot.bin,0x90000000（sdram的起始地址是0x90000000），然后用g命令跳到地址处执行。
  下面我要观察串口是否初始化，是否有数据输出，继续看data sheet串口uart部分，写一段小代码，测试吧。。。。。