Content originally posted in LPCWare by nerd herd on Tue Jan 20 15:07:00 MST 2015
Hi vladimirro,
I can understand your confusion. The reason why two different sets of pins can function as UART0 is to give the user flexibility with multiplexed pins. The way we go about this is based on the value of certain bits in the IOCON register. That said, ISP programming happens after a reset, meaning the pins have a default state in what their function are upon reset. In this case, PIO0_1 and PIO_02 are the only UART0 pins you can use for ISP programming. If you look at the user's manual one more time, you will notice that those are the only UART0 pins that explicitly say they can be used for ISP programming.