求教：5509A读取SD卡阻塞

SD卡是1G的FAT32格式的
我是调用CSL库函数进行操作的，在例程中加入MMC_read函数程序貌似就卡住了，查看了下网上的资料感觉像是阻塞，具体现象如下：正常现象：
MMC Controller setup test...
SD card found
Asking SD card for its RCA...
RCA sent is 0xb368
Initialized card successfully
TEST PASSED
加了MMC_read函数的现象
MMC Controller setup test...
SD card found
Asking SD card for its RCA...
RCA sent is 0x
程序代码：
void main()
{
  Uint16 mybuf[256],i,mybuf1[256];
  CSL_init();
  PLL_config(&myConfig);
  printf ("MMC Controller setup test...\n");
  mmc0 = MMC_open(MMC_DEV1);
  MMC_setupNative(mmc0,&Init); //initialize the MMC controller
//  MMC_getConfig(mmc0,&test);
  MMC_sendGoIdle(mmc0); //Sends a broadcast GO_IDLE command
  for (count=0;count<4016;count++)
  asm("        NOP");
  cardtype = MMC_sendOpCond(mmc0,0x00100000); //Sets the operating voltage window while in Native mode
  if (cardtype == 0xFFFF){
     printf ("Card not recognized\n");
     exit(0);
  }
  //MMC_setCardType(card, cardtype);
  if (cardtype == MMC_CARD){
     printf ("Setting 10 as RCA value\n");
     cid = &cardid;
     /* Instruct all cards to send their Card Identification Data    */
     MMC_sendAllCID(mmc0,cid); // get the CID structure for all cards.
     card = &cardalloc;
     //retVal = MMC_setRca(mmc0,card,0x8DAB);
     retVal = MMC_setRca(mmc0,card,2);
     /* The host can request for the CSD in the standby state. This   *
      * structure contains the data outlined below                    */
     printf ("Reading CSD structure for MMC card\n");
     csd = &cardcsd;
     retVal=MMC_sendCSD(mmc0);
     MMC_getCardCsd(mmc0, csd);
  } else {
     printf ("SD card found\n");
     cid = &cardid;
     /* Instruct all cards to send their Card Identification Data    */
     SD_sendAllCID(mmc0,cid);
//     printf ("The values in the CID of the SD card are:\n");
     printf ("Asking SD card for its RCA...\n");
     card = &cardalloc;
     rca = SD_sendRca(mmc0,card);
     printf ("RCA sent is 0x%x\n", rca);
     /* The host can request for the CSD in the standby state. This   *
      * structure contains the data outlined below                    */
     retVal = MMC_sendCSD(mmc0);
//     sdcsd = &sdcardcsd;
//     SD_getCardCsd(mmc0, sdcsd);
  }
  retVal = MMC_selectCard(mmc0,card);
  MMC_read(mmc0,0x238200,mybuf,256);
  for(i=0;i<6000;i++);
  printf ("Initialized card successfully\n");
  printf ("TEST PASSED\n");
  while(1);
}