maybe you could use a separate sdram controller. i remember i once did a design for a processor running at 17mhz. the external sdram controller and the sdram were running at 34mhz. so the processor was able to access the sdram like static ram, without taking care of any refresh cycles, which were automatically handled every 32ms. tino Tony Nixon Gesendet von: pic microcontroller discussion list 08.05.02 04:07 Bitte antworten an pic microcontroller discussion list An: PICLIST@MITVMA.MIT.EDU Kopie: Thema: Re: [PIC]: dynamic RAM Benjamin Bromilow wrote: > > >From: Herbert Graf > > >Yhe real killer though is refresh, which has to be done continuously. TTYL > > How continuous is continuous? It would appear to be impossible to refresh > all the bits of data simultaneously. How often is this needed? Or does it > depend upon the memory used?? > I'm curious because it looks like I'm going to have to use some seriously > big, fast memory chips in my next PIC based project and I'm a bit wary. > I've read the PIClist simm source code but I still lack total enlightenment! My code could be optimised further I suppose, but it took 2 minutes for the code to completely write to a 4 Meg SIMM with a full refresh every 4mS. The refresh is using about 25% of processor time. It's murder downloading that much RAM back to the PC serial port. About an hour at 19200 baud. :-(( Definitely a job for USB or parallel port. -- Best regards Tony mICros http://www.bubblesoftonline.com mailto:sales@bubblesoftonline.com -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics