AVR-Chat

Thanks a lot for everyone's input on the DRE interrupt.   I'll probably use
it at some point.   Steve

 

From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com] On Behalf
Of Clark Martin
Sent: Friday, May 18, 2012 9:01 AM
To: AVR-Chat@yahoogroups.com
Subject: Re: [AVR-Chat] Re: USART Interrupts

 

  



Sent from an iPhone, but is it mine?

On May 18, 2012, at 6:47 AM, "Steven Hodge" <steve@terrafirma.us
<mailto:steve%40terrafirma.us> > wrote:

> This is somewhat of an aside. I just finished porting my USART ISR's from
> mega to xmega. They only use the Receive Complete (RXC) and Transmit
> Complete (TXC) interrupts. I've always been curious as to when one would
> use the "Data Register Empty" (DRE) interrupt. Can somebody give a brief
> reason when and why to use this one? Thanks, Steve
Normally you use the DRE for sending out serial data. This gives you the
highest data rate. Using TxC adds a short space between characters. 

In my RS-485 code I use DRE to send the data then TxC to switch the bus
transceiver to receive when the packet has been sent. 

One important point is that DRE will generate an interrupt any time the
buffer is empty. So you need to disable the DRE interrupt enable bit when
you have sent the last byte. Otherwise it will continue to call the service
routine. 
> 

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