[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Re(2): Re(2): External DMA interrupts



Hi  Arne,

No, you won't miss the interrupt unless you mask it off. The external
DMA interrupt is generated when the run bit *is* clear. If the complete
transfer is finished the run bit will be cleared, and the interrupt
will occur when you enable it.

Best regards

Per Zander

On Thu, 6 Mar 2003, Arne Bockholdt wrote:

> Hi Per.
> >
> >Do you get the data out on the external DMA channel as expected ?
> 
> Yes.
> >
> >
> >One reason could be if you enable the external DMA interrupt (in the 
> >interrupt mask) before you start the external DMA channel. Possibly there
> >is also a small latency after giving the start command to the external
> >DMA 
> >channel until it is actually started.
> 
> Yes, i had the external DMA interrupt enabled *before* I started the
> external DMA. I thought that the interrupt will be triggered when the run
> bit will be cleared, not when the run bit *is* clear. After this change in
> the code I receive only one interrupt, the expected one. 
> One final question : If I enable the interrupt after starting the channel,
> what happend when DREQ ist still high ? Is it possible to loose an
> interrupt because the transfer has been started/finished (e.g. burst mode,
> only one burst) before I enable the interrupt ? 
> >
> >I hope this helps
> 
> Yes, thanks a lot !
> 
> 	Arne Bockholdt
> >
> 
> Dipl. Inform. Arne Bockholdt
> REA Elektronik GmbH
> Teichwiesenstr. 1
> 64367 Mühltal-Waschenbach
> Tel. +49 (0) 6154 / 638-115, Fax -195
> ABockholdt@xxxxxxx.de
>