uboot内使用mmc read命令读取emmc错误

bonoy0328

在学习I.MX6U嵌入式开发第三十章30.4.5 EMMC和SD卡操作命令，第717页的mmc read命令时出错。首先板子是可以正常启动，官方的系统没有修改
进入uboot后操作如下：
=> mmc list
FSL_SDHC: 0
FSL_SDHC: 1 (eMMC)

=> mmc dev 1 0
switch to partitions #0, OK
mmc1(part 0) is current device

=> mmc read 80800000 600 10

MMC read: dev # 1, block # 1536, count 16 ... 16 blocks read: OK

=> md.b 80800000 2000
80800000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ...........
80800010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ...........
80800020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ...........
80800030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ...........

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省略中间部分
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80801fd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ...........
80801fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ...........
80801ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ...........

和实验中的结果不同，全都是0，请问为什么呢？谢谢各位大佬