Content originally posted in LPCWare by NXP_USA on Wed Feb 17 16:43:54 MST 2010
Quote: richas
I tried disconnecting SWO, reset, and the pullup on reset. (These are R31, R32, and R33 on the LPCxpresso board)
Debug did not function. It will work without SWO (what IS SWO?) or the pullup on reset but not without the reset signal itself.
Rich
Which pins are needed depends on what debug functionality is required. It is possible to connect to the part with just SWD and ground, but not with the LPCXpresso free toolchain because it always resets the part and reprograms it when entering debug. If you wish to use Trace features which are in the full Red Suite/Red Probe tools but not the free LPCXpresso tool, then you would need to connect SWO as well.
-NXP