LPC11E6x confusing data: U0_RXD and U0_TXD pins appear twice?

[accelmotion]

Reading the LPC11E6x datasheet shows two sets of U0_RXD and U0_TXD pins, one pair noting it works only for ISP and the other with no comment. The USART0 pin list doesn't comment on the two sets or what's different or the same between them, and neither does anything I could find in the User Guide. The 'ISP' pair are available for all sizes of package so you'd expect that to be the real global USART0 RXD and TXD... I'm confused, obviously. 

What's the deal on these two seemingly identical sets of U0_RXD and U0_TXD pins?

[Alice_Yang]

Hello David Smith ,

This means you can choose any one of them as  U0_RXD and U0_TXD using pin control register. 

There is sample code for UART, you can have a look at how to configure the UART pins, 

then you will know it well. 

https://www.nxp.com/downloads/en/lab-test-software/SC_LPC11XXLV_PERIPHERALS_USING_KEIL_MDK-ARM.ZIP

LPCopen:

LPCOpen Software for LPC11XX | NXP  

https://www.nxp.com/products/processors-and-microcontrollers/arm-microcontrollers/general-purpose-mc...

Have a great day,
TIC

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[accelmotion]

No, this does not make sense. Why create pins (in the case of the 100-pin part) 94 and 20 to do the same thing? I cannot tell if you have this answer right, or even if you understand my question. Your answer does not illuminate why there are two pins with the same name...

[Alice_Yang]

Hello David,

Each pin can used not only one function.

For example the pin94(100-pin part) (PIO0_18)you mentioned, you can configure it as U0_RXD function,

also can used to CT32B0_MAT0, or gpio PIO0_18.

For some customer, they may be used this pin as CT32B0_MAT0 function, then they only can use the pin20 as U0_RXD. If there is only one U0_RXD, how does customer use UART0 if the only pin has been used. 

Have a great day,
TIC

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