Jaap van Ganswijk wrote: > At 2004-07-15 16:48, docydoc wrote: > > >Jaap van Ganswijk wrote: > > > >You'll used DMA when you have a controller pushing your A/D-data > >directly into the main memory of the host system. > >Otherwise you'll have a driver or something similar that work with > >the CPU which is not DMA. > > A driver is software and can work with either interrupts > or DMA. Your sentence doesn't seem to make sense. >
I meant data transfer without the processor. If the driver (software)does (as you said by interrupt) - it's not DMA. IMHO DMA makes no sense if you transfer just a few byte because DMA needs to be set up. So memory needs to be installed on the AD board so it can be tranfered (per DMA) to the main processors memory. But at data rate of 390k/s I would not do it. Also the aquisition board must be able to do DMA. > >I would not worry about it too much. Don't mess around with DMA > >programming at these data rates except you want to buffer in your > >application, If big blocks of mem should be transferred DMA. If not no DMA I'd suggest. I already said it. > Of course he wants to buffer it in his application, because it's > not a steady stream he is handling. It's not? What are 400k samples of 8 bits data then? Samples as burst of 4M samples in a 10th of seconds and the silence? I don't know the exact application But how much buffering? 16 Bytes? I talk about big data blocks (16kB at least for a DMA). DMA needs bus arbitration and killing the time with it is not so nice :-O > Huh and now you start advocating a stand-alone board with a DSP? Hmpf. No I don't. Was just a thought. Some people may want to do this. Some people want to transfer a few bytes using a dma controller. I personally won't :-) I already programmed DMA in some nowadays anchient systems and fear a little doing that again. So if possible and not reall necessary I won't use DMA. > And to top it of, suddenly you think that DMA does make sense? It depends on the task to do. I just wanted to show a few pro and cons. > You even confuse me! Was not my intention . . . Pierre -- Author: docydoc INET: [EMAIL PROTECTED] Fat City Hosting, San Diego, California -- http://www.fatcity.com --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB CHIPDIR-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
