UART Tx to Tx connecting issues

[mcschandru]

Hi,

1)I know we should connect Tx-Rx and Rx- tx. But I like to know What happens if Tx to Tx is connected accidentally?
Will it burn UART?
I came to know if you using resistor then the current flow will be low and the UART will not be spoiled.

2)What is USART?
Is it a communication protocol or it is a hardware that needs protocol for communication?

Any suggestion please?


Regards
Chandru

 

[internetuser2k12]

A in UART and USART stand for Asynchronous, S in USART stand for Synchronous.

 

[alexan_e]

Also U stands for universal, R for receiver and T for transmitter.
Did this reply any of the OP questions?

 

[mcschandru]

Hi,

Thankyou. That means both UART and USART are communication protocol. Rite?


Chandru.....

 

[alexan_e]

Note that the microcontrollers use a logic level Rx/Tx so a device like MAX232 should be used to translate it to the proper RS232 levels.
If you connect Tx with Tx (I assume you refer to max232) then the chips will overheat, they may not be damaged.
Normally the connection is made using a straight wire but if you want to use a resistor for testing purposes then you can do it and it can limit the current in case of a wrong connection.
Also note that apart form the Tx and Rx lines the ground should be connected too.
In order to use the USART you have to set up the internal registers of the peripheral (you are referring to a microcontroller right) to control the receive/transmit mode, data and rate.

 

[betwixt]

No they are not protocols, they are functional devices, available as integrated peripherals or discrete devices.

UART and USART are basiclly the same, they do the same job of converting serial data but the 'S' (synchronous) means it can also package and extract bits at a speed decided by an external cloock as well as an internal one. It's a confusing difference as most UARTS can also be used synchronously.

Connecting RX to RX will not cause any harm as they are both inputs and there is no source of power to damage them.
It is possible to cause damage by connecting TX to TX because one could be driving high while the other drives low and hence short out the power souce. However, this is unlikely to happen because most serial drivers these days have protection of some sort and those generating their own RS232/V24 voltages usually can't provide enough current to damage their output stages.

A protocol is the method used to prepare the data so it can be sent serially and recovered reliably at the other end of the link. Sometimes this is done in hardware, sometimes in software but it has nothing to do with the electrical signals present in the link.

Brian.

 

[mcschandru]

Hi Alexan & Betwix,

Thankyou very much. It really helps me to understand about UART. I read in some text book that " USCI (Universal serial Communication Interface) supports SPI, I2C and UART protocols" and moreover while refering the forum also.
https://www.edaboard.com/threads/69740/


Thanks
Chandru....