Post by thread:[PIC]: CAS/RAS

Erm.. and now I've woken up.... ----- Original Message ----- From: "Jon Baker" <spam_OUTjonTakeThisOuTHAYSEED.NET> To: <.....PICLISTKILLspam@spam@MITVMA.MIT.EDU> Sent: Wednesday, May 01, 2002 9:02 AM Subject: Re: [PIC]: CAS/RAS > for cAS before RAS: > CAS low for counter=1 to n_rows RAS low wait RAS high next CAS high > > Does CAS go LOW, then RAS gets cycled for each ROM address, then CAS > > goes HIGH again? > > I think that is a hidden refresh, and not all dram supports it. Hidden refresh is a type of cas before ras refresh but differs in that it can take place immediately after a data transfer and before cas is returned high again. You can also pulse ras more than once before returning cas high to do a burst refresh- hidden refresh has the addvantage that the data presented on the bus after a read remains valid even though you are refreshing the dram. -- Jon Baker I'll be quiet now. -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestKILLspammitvma.mit.edu

Jon Baker wrote: > > Erm.. and now I've woken up.... Cough gag splutter...Me too [yawn] {Quote hidden}> > > for cAS before RAS: > > > CAS low > for counter=1 to n_rows > RAS low > wait > RAS high > next > CAS high I thought that may be the case. I used and modified the code that I found on the PIClist about SIMM interfacing. It has a loop like this, which I thought was a bit odd.. for anotherCounter=1 to 32 CAS low for counter=1 to 8 RAS low wait RAS high next CAS high next I guess it achieves the same thing though. Many thanks -- Best regards Tony mICros http://www.bubblesoftonline.com .....salesKILLspam.....bubblesoftonline.com -- http://www.piclist.com hint: To leave the PICList EraseMEpiclist-unsubscribe-requestspam_OUTTakeThisOuTmitvma.mit.edu

> Jon Baker wrote: > > > for cAS before RAS: > > > > > CAS low > > for counter=1 to n_rows > > RAS low > > wait > > RAS high > > next > > CAS high > "Tony Nixon" wrote: {Quote hidden}> I thought that may be the case. I used and modified the code that I > found on the PIClist about SIMM interfacing. It has a loop like this, > which I thought was a bit odd.. > > for anotherCounter=1 to 32 > CAS low > for counter=1 to 8 > RAS low > wait > RAS high > next > CAS high > next > > I guess it achieves the same thing though. I find that a bit strange, I thought that the action of lowering the CAS reset the internal address counter- so in your example ( if this is the case ) only the first 1/32 of the memory would get refreshed. I'll see if I can find a datasheet and get the definitive answer- but then, like Michael said.. if its working, then its probably right :) -- Jon Baker -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Jon Baker wrote: > > > > for anotherCounter=1 to 32 > > CAS low > > for counter=1 to 8 > > RAS low > > wait > > RAS high > > next > > CAS high > > next > > > > I guess it achieves the same thing though. > > I find that a bit strange, I thought that the action of lowering the CAS > reset the internal address counter- so in your example ( if this is the > case ) only the first 1/32 of the memory would get refreshed. I'll see if I > can find a datasheet and get the definitive answer- but then, like Michael > said.. if its working, then its probably right :) I looked fairly hard around the web for a data sheet on the M5M44100 chips from Mitsubishi and failed. I got these old 4Meg SIMMS for free which is why I'm using them. I've written to the SIMM and filled it with the alphabet repeating over and over. I've left the power on for over 24 hours and read back and compared the data and there were no errors reported, so I guess the code I am now using works. -- Best regards Tony mICros http://www.bubblesoftonline.com salesspam_OUTbubblesoftonline.com -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Tony, try to change the refresh algorythm to 512 consecutive (is that your page size) normal reads. It should refresh on read. Peter -- 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