自制的28335板子与ccs3.3连接不上

我自己设计了三块28335控制板，有两块正常，有1块与ccs3.3连接不上。我用示波器测试了一下jtag，tclk信号正常，tdi有信号，tdo没有信号。ccs连接时间较长，然后出现Error connecting to the target:

Error 0x00001200/-1031

Error during: OCS, Target,

Device driver: Problem with the Emulation Controller.

It is recommended to RESET EMULATOR.  This will disconnect each

target from the emulator.  The targets should then be power cycled

or hard reset followed by an emureset and reconnect to each target.

I/O Port = 240

Board Name: F28335 XDS510 Emulator

Cpu Name: CPU_1

Abort: Close Code Composer Studio.

Retry: Try to connect to the target again.

Cancel: Remain disconnected from the target

Diagnostic: Run diagnostic utility.

这是怎么回事呢？难道是芯片坏了？另外，我设计的板子有时候后莫名其妙出现芯片的1.9V与地短路现象，我已考虑esd问题了，也加上esd保护芯片，这是怎么回事呢？