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[on:]

Hi all

The list of the ports on Mega page says "Serial: 0 (RX) and 1 (TX); Serial 1: 19 (RX) and 18 (TX); Serial 2: 17 (RX) and 16 (TX); Serial 3: 15 (RX) and 14 (TX)". But in the schematic there is atleast TX2/RX2 at pins 13 and 12. Are those pins serial ports, is there a reason they are missing from the text listing. What is the correct list.

By the way the Megas web page text is funny. It almost looks like the first serial port RX pin is connected to the pin #0. Quite a rare ic.

[Reply #1 on:]

Are those pins serial ports,

No. Not with the meaning of serial that you mean.

They are other forms of I/O, see the data sheet for what.

It almost looks like the first serial port RX pin is connected to the pin #0.

It is.

[Reply #2 on:]

I am LMI "at home".

No. Not with the meaning of serial that you mean.

They are other forms of I/O, see the data sheet for what.

What is the difference. They are marked as Usart on datasheet. And on the schematic diagram they look similar to other serial ports. But the list on the text does not mention them.

Are you perhaps saying that is an error on the Arduino web site.

[Reply #3 on:]

They are marked as Usart on datasheet.

Yes they are the pins for the USART, when you use serial data you are using a UART

UART ( Universal Asyncronous Receiver Transmitter )
USART (Universal Syncronous Asyncronous Receiver Transmitter )

The sort of serial data you use talking with computers, downloading code is an asyncronous code. This means that each byte is synchronised with a start bit at the beginning and a stop bit at the end.
With synchronous data no such information is sent and the data must be synchronised an other way, like transmitting a clock or framing packets of data with special patterns.