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F28芯片下载加密软件后,硬件信号固定,无法连接解密。

F28035芯片,XDS100 V2或XDS510仿真器。

当下载加密软件后,用CCS8.3仿真连接或uniflash,都无法连接解密。

硬件是固定的,无法切换boot模式等。

请问如何解密下载软件?有的好的方法。谢谢。

Green Deng:

应该来说,解密的时候将boot模式切换到wait模式是必须的,F28035的TRM中有讲到:
This device does not support the hardware wait-in-reset mode that is available on other
C2000 parts. The "wait" boot mode can be used to emulate a wait-in-reset mode. The "wait"
mode is very important for debugging devices with the CSM password programmed (that is,
secured). When the device is powered up, the CPU will start running and may execute an
instruction that performs an access to an emulation code security logic (ECSL) protected
area. If this happens, the ECSL will trip and cause the emulator connection to be cut. The
"wait" mode keeps this from happening by looping within the boot ROM until an emulator is
connected.

Ccc Chen:

请问,如果JTAG的TRST引脚上拉到5V有没问题,上拉2K分压后2.5V连接到TRST引脚上。

Green Deng:

回复 Ccc Chen:

理论上不可以,接入芯片的电压不能超过3.3V。

Ccc Chen:

回复 Green Deng:

分压后,实际2.5V到TRST,也不可以?

Green Deng:

回复 Ccc Chen:

这么说吧,如果你实在没办法设置成3.3V,那2 ~ VDDIO+0.3 V的电压值都可以,但是会不会影响使用效果和使用期限,这个就没办法保证了

Ccc Chen:

回复 Green Deng:

使用效果和期限?你的意思是可能有损害MCU?

Green Deng:

回复 Ccc Chen:

对啊,不符合标准电压,肯定对芯片会有损害。当然具体会以什么样的情况出现,以及具体时间,这个都不好说

Ccc Chen:

回复 Green Deng:

谢谢,
我现在把仿真器拆进去,把XDS100V2仿真器板上的3.3V连接到TRST脚上,这样应该没什么问题吧。

Green Deng:

回复 Ccc Chen:

我认为可以,具体的你可以参考一下引脚说明:
JTAG test reset with internal pulldown. TRST, when driven high, gives the scan
system control of the operations of the device. If this signal is not connected or
driven low, the device operates in its functional mode, and the test reset signals
are ignored. NOTE: TRST is an active high test pin and must be maintained low
at all times during normal device operation. An external pulldown resistor is
required on this pin. The value of this resistor should be based on drive strength
of the debugger pods applicable to the design. A 2.2-kΩ resistor generally offers
adequate protection. Because this is application-specific, TI recommends
validating each target board for proper operation of the debugger and the
application. (↓)

Ccc Chen:

回复 Green Deng:

好的,谢谢!

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