Hi, DuKang,
The circuit in the red circle is downloading/debugging circuit, as you know that LPC8N04 has two pins PIO0_10/PIO0_11 as SWD port, with pin 2&4 closed for P7 and P8 jumper, the SWD signals of LPC8N04 is connected to the debugging chip LPC11U35, so you can download/debug the LPC8N04 with usb port of chip LPC11U35.
Hope it can help you
BR
XiangJun Rong
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