RE: [avr-chat] UART TXC

[Schwichtenberg, Knut]

Hi,
you should think of half duplex connections like RS485. After the last
bit of the current transmission is out, the trsmitter has to be switched
of and the receiver to be activated! With a full duplex connection you
don't have this problem. There is a SPI to Serial converter from MAXIM
that gives you only a UDRE equivalent interrupt. There you need an extra
character to be send.

Cheers

Knut

> -----Original Message-----
> From: 
> address@hidden 
> [mailto:address@hidden
u.org] On Behalf Of Bjarne Laursen
> Sent: Tuesday, February 27, 2007 8:11 AM
> To: address@hidden
> Subject: Re: [avr-chat] UART TXC
> 
> Flemming Gram Christensen skrev:
> > Hi list.
> >  
> > What is the reason that the TXC bit is not cleared when you write a 
> > byte into UDR?
> > I am using a mega169, but the other devices do probably 
> behave similar.
> >  
> > The TXC bit is set when the last bit in the UART shift register is 
> > transmitted and UDR does not contain a byte to transmit. The bit is 
> > cleared then the transmit complete interrupts is executed 
> and can be 
> > cleared manually in software.
> > Why is it not cleared also when starting transmission of a new byte?
> I am guessing here, but:
> The TXC could be seen as a tx underflow indicator. If it was cleared 
> automatically you could loose this information. Normally when 
> transmitting continuously data you would want to use the UDRE 
> bit, that 
> tells that you can send more data.
> 
> -Bjarne Laursen, RoseTechnology A/S, Denmark
> 
> 
> _______________________________________________
> AVR-chat mailing list
> address@hidden
> http://lists.nongnu.org/mailman/listinfo/avr-chat
>