CRP for LPC2132

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#application #加密 #command #flash #dll #up

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本文针对J-Link无法识别ARM芯片的问题进行了分析，主要包括硬件连接不当及ARM芯片内部启用CRP功能两大原因，并提供了相应的解决方法。

SEGGER J-Link Commander V4.46a ('?' for help)
Compiled Apr 13 2012 19:32:19
DLL version V4.46a, compiled Apr 13 2012 19:32:02
Firmware: J-Link ARM V8 compiled Dec 1 2015 11:42:48
Hardware: V8.00
S/N: 20080643
Feature(s): RDI,FlashDL,FlashBP,JFlash,GDBFull
VTarget = 3.229V
Info: Could not measure total IR len. TDO is constant high.
Info: Could not measure total IR len. TDO is constant high.
No devices found on JTAG chain. Trying to find device on SWD.

WARNING: RESET (pin 15) high, but should be low. Please check target hardware.

WARNING: RESET (pin 15) high, but should be low. Please check target hardware.
No device found on SWD.
Did not find any core.
Info: Could not measure total IR len. TDO is constant high.
Info: Could not measure total IR len. TDO is constant high.
No devices found on JTAG chain. Trying to find device on SWD.

WARNING: RESET (pin 15) high, but should be low. Please check target hardware.

WARNING: RESET (pin 15) high, but should be low. Please check target hardware.
No device found on SWD.
Did not find any core.
J-Link>

出现上述问题的原因主要有以下几个方面：

【1】硬件连接,可以按照NXP官方提供的标准接法如下图

需要检查ARM芯片的JTAG定义的引脚和JLink接口定义的引脚一一对应(注，这里是10PIN接头)，如下图

如果硬件连接没有问题，需要检查各连线之间有没有虚焊，然后再JLink的命令窗口的"J-Link>"提示符后面键入"r"命令，用示波器分别测量TCK、TDI、TDO引脚的信号，如果正常，是可以测量到脉冲信号的。

【2】ARM芯片内部使能了CRP(Code Read Protection)功能

如果LPC系列的ARM芯片使能了CRP功能，JLink将无法读取ARM内部寄存器的内容，从而不能找到ARM core ID。
详细信息请参考LPC2100系列ARM7微控制器的加密方法和LPC2478加密设置（LPC）（加密）

If the CRP has been enabled, there is nothing J-Link can do to erase the device since the JTAG interfaceis disabled.
The LPC devices provide a so called ISP mode (UART communication) in which a device erase command can be sent to mass erase the device which also causes the CRP to be lifted.

If the CRP is disabled but there is a malfunctioning application in the flash memory which for example locks-up the device by incorrectly setting up the PLL or things like that
which also prevents a connection via JTAG and makes it impossible to identify the core,
you can force the device to boot in ISP mode which does not start the application but the JTAG interfaceis enabled.
In this mode the device can easily be erased via J-Flash, Flasher ARM etc.

此种情况，可以使用ISP清除CRP。