Hi Haipeng,
Please try to download this lpcopen code for IAR and MDK:
http://www.nxp.com/assets/downloads/data/en/software/lpcopen_2_10_keil_iar_nxp_lpcxpresso_1769.zip
Then use your JLINK to download the code in the IAR or MDK project to the LPCXpresso LPC1769 board, whether that can be ok?
If yes, this problem maybe caused by the JLINK GDB, you need to contact with Segger, they may from the JLINKGDB side give more professional answer.
About the JLINK GDB, you can contact with Segger from this link:
Main Page - SEGGER Forum
Wish it helps you!
If you still have question about the LPC, please let me know!
Have a great day,
Kerry
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