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李奂善

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[问答]

请问CSM解密过程中的伪读(dummy read)有什么作用?


请教一下,上述例子中dummy read的作用是什么?为什么叫dummy read呢?感觉好像有些多此一举? 还有如果将正确密码写入了解密寄存器,那么CSMSCR的最低位就应该自动清零了吧?   另外加密时,写入密码后,最后还要forcesec一下才能锁定?看了一些例子都没有添加这个,不知为何? 多谢指教!

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周静

2018-9-4 11:14:35
代码需要执行dummy read,手册TMS320x2833x, 2823x System Control and Interrupts Reference Guide第 4.3.2 Password Match Flow流程图比较清晰看到其作用,CSMSCR最低位仅可读取。通过对DSP2833x_CSMPasswords.asm写入密码,编译后烧录完成对芯片加密。
Even if a device is not protected with a password (all password locations all ones), the CSMwill lock at reset. Thus, a dummy read operation must still be performed on these devices prior to reading, writing, or programming secure memory if the code performing the access is executing from outside of the CSM protected memory region. The Boot ROM code does thisdummy read for convenience.
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李奂善

2018-9-4 11:29:41
引用: euagh1985 发表于 2018-9-4 18:00
代码需要执行dummy read,手册TMS320x2833x, 2823x System Control and Interrupts Reference Guide第 4.3.2 Password Match Flow流程图比较清晰看到其作用,CSMSCR最低位仅可读取。通过对DSP2833x_CSMPasswords.asm写入密码,编译后烧录完成对芯片加密。
Even if a device is not protected with a password (all passwor ...

非常感谢!
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