AVR-Chat

A hardware uart is almost always better unless you need some non-standard 
protocol. You use software uarts when you run out of hardware, or don't 
want to spend the money on an external uart chip.

Software uarts are not too bad if the baud rates you are dealing with are 
low enough.
  I have a mega8 project with 3 uarts. One hardware and two software. But 
the software uarts are only running at 4800 baud max.
   Need a Int0/1 pin and a timer for each uart. There are ways to 
oversample and use only a single timer for multiple channels, but now you 
are using quite a bit of software overhead.

    As David pointed out a very good case for interrupts.

  There is a thread about this with some links to applications notes on 
AVRfreaks. But as we know the freaks site is down due to some juvenile 
hacking. We'll see how long it takes them to plug the holes in the php 
forum code.



-carl


At 09:09 PM 7/31/2005, you wrote:

>Im working in a project with atemega8 and atemega32, for this work is
>necessary 3 serial ports, and I cant loose any data, but what happen if
>two or more ports have incoming data at the same time?, what can I do?,
>other question is what is the adventage for use usart hardware or usart
>software?.
>
>Sounds like a good case for using interrupts.
>Software uarts require a fair bit of software overhead to run, but if you
>need three uarts, you're pretty much stuck with that.
>
>OTOH, I seem to remember a data sheet for an AVR with four hardware uarts.