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lpc 1768 data sheet doubt

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raman00084

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i am designing lpc1768 pcb, when looling at lpc1768 data sheet from nxp the uart are repeated uart1 is repeated two times, uart2 is repeated two times and finally uart3 is repeated 3 times
p0(0) - TXD3
p0(1) - RXD3

p0(25) - TXD3
p0(26) - RXD3

p4(28) - TXD3
p4(29) - RXD3

p0(10) - TXD2
p0(11) - RXD2

p2(8) - TXD2
p2(9) - RXD2


THE PWM IS ALSO REAPTED LIKE

P1(18)-PWM(1) CHANNEL1
P2(0)-PWM(1) CHANNEL1


KINDLY TEL WHICH I/O I MUST USE FOR THE FOLLOWING

UART1
UART2
UART3

PWM


THANK YOU


p0(15) - TXD1
p0(16) - RXD1

p2(0) - TXD1
p2(1) - RXD1
 

The reason for the multiple available pins for the UARTs are the sharing of functions. Each IO-pin has several possible functionalities, and you need to select the combination you want to use in your application.

Most pins have 2-4 different possible uses, and you have to go through your design and find which selection you want to use, and if it is possible to combine it with the available IO-combinations.
It's like at big puzzle, at least if you need many of the functions.

BTW P0(0) is not the pin number, but the IO port number, and the pin number is 37.
 
The usage of multiple UARTs depends on the PINSEL register.
Better to go for
UART1-->P2.0 & P2.1
UART2-->p2.8& p2.9
UART3-->P4.28 & P4.29

These are perfectly worked with my board.
 

The first thing you need to do, is to list all the functions you need in your design, like PWM, UARTs including control signals,CAN, analogue IO, timer/counters, USB, Ethernet.
Then you need to look through the pin/function list and see if this is possible to combine. Many times you will need to make a changes to solve the puzzle completely.

Sometimes there is not enough pins for the funtions you need, and then you'll need to redesign your needs, or change to a bigger processor/larger footprint, with the pins available. Most processor families have several variants of the same silicon, with more or less RAM/Flash/IO available.

This is also why we can't tell you which pins to select, since we only know a small part of your design.
 

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