Searching \ for '[PIC]: dynamic RAM' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/microchip/devices.htm?key=pic
Search entire site for: 'dynamic RAM'.

Exact match. Not showing close matches.
PICList Thread
'[PIC]: dynamic RAM'
2002\04\21@214355 by Tony Nixon

flavicon
picon face
Hi all,

Has anyone interfaced a PIC to RAM SIMM modules.

Any pointers?

--
Best regards

Tony

mICros
http://www.bubblesoftonline.com
spam_OUTsalesTakeThisOuTspambubblesoftonline.com

--
http://www.piclist.com hint: To leave the PICList
.....piclist-unsubscribe-requestKILLspamspam@spam@mitvma.mit.edu


2002\04\21@223845 by Herbert Graf

flavicon
face
> Hi all,
>
> Has anyone interfaced a PIC to RAM SIMM modules.
>
> Any pointers?

       I don't know of any off hand but dynamic memory is pretty easy to figure
out. Usually you just strobe in the row and column of what you want to
access and then you access it, it's a little more complicated then static
ram but you save a little on I/O pins. The real killer though is refresh,
which has to be done continuously. TTYL

--
http://www.piclist.com hint: To leave the PICList
piclist-unsubscribe-requestspamKILLspammitvma.mit.edu


2002\04\21@223901 by Vit

picon face
> Hi all,
>
> Has anyone interfaced a PIC to RAM SIMM modules.
>
> Any pointers?

Tony,

Have you tried searching Google or Piclist.com?  :)

http://www.piclist.com/techref/microchip/picsimm.htm

Sincerely,

Vitaliy

--
http://www.piclist.com hint: To leave the PICList
.....piclist-unsubscribe-requestKILLspamspam.....mitvma.mit.edu


2002\04\21@224034 by Vit

picon face
Also, check this out:  http://www.simmstick.com/

--
http://www.piclist.com hint: To leave the PICList
EraseMEpiclist-unsubscribe-requestspam_OUTspamTakeThisOuTmitvma.mit.edu


2002\04\22@010236 by Heinz Czychun

flavicon
face
Hi Tony,

       Have a look at http://www.tech-tools.com/hwt12.htm. This should be
extendable from a single chip to a SIMM. It also explains the refresh thing
fairly well. A good starting point.

Heinz


At 11:40 AM 4/22/2002, Tony Nixon wrote:
{Quote hidden}

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads



'[PIC]: dynamic RAM'
2002\05\07@200424 by Benjamin Bromilow
flavicon
face
>From:         Herbert Graf <KILLspammailinglistKILLspamspamFARCITE.NET>

>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!

Ben

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads


2002\05\07@211858 by Herbert Graf

flavicon
face
> >From:         Herbert Graf <RemoveMEmailinglistTakeThisOuTspamFARCITE.NET>
>
> >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!
>
> Ben

       You are right, it depends on the memory, it is most definately listed in
the datasheet of the memory in question. FWIW my experience has shown that
the refresh they recommend is not 100% necessary, I've gotten away with MUCH
longer times between refreshes, however if you need 100% data integrity use
the specified refresh. TTYL

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads


2002\05\07@220940 by Tony Nixon

flavicon
picon face
Benjamin Bromilow wrote:
>
> >From:         Herbert Graf <spamBeGonemailinglistspamBeGonespamFARCITE.NET>
>
> >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
TakeThisOuTsalesEraseMEspamspam_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


2002\05\08@021617 by Martin Buehler

flavicon
face
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 <RemoveMETony.NixonspamTakeThisOuTENG.MONASH.EDU.AU>
Gesendet von: pic microcontroller discussion list <PICLISTEraseMEspam.....MITVMA.MIT.EDU>
08.05.02 04:07
Bitte antworten an pic microcontroller discussion list


       An:     EraseMEPICLISTspamMITVMA.MIT.EDU
       Kopie:
       Thema:  Re: [PIC]: dynamic RAM


Benjamin Bromilow wrote:
>
> >From:         Herbert Graf <RemoveMEmailinglistEraseMEspamEraseMEFARCITE.NET>
>
> >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
RemoveMEsalesspam_OUTspamKILLspambubblesoftonline.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


2002\05\08@033017 by Alan B. Pearce

face picon face
>How often is this needed? Or does it
>depend upon the memory used??

It used to be that you needed to cycle through the 7 bit recycle address
range in 1mS with early dynamic chips. Later larger chips expanded this to
2mS for the 8 bit recycle address range. These all required the recycle
address to be externally generated, and some people went to the extent of
working out if a particular address had been accessed during the previous
recycle period for that address, and skipped that address refresh request so
that the CPU did not get held up on memory accesses.

The newer chips with built in recycle address counters I believe are set up
to require the same recycle request rate as the 256 in 2mS and the size of
the recycle address counter is invisible to the user. However as always
there is the caveat - read the data sheet for the chip! I would go as far as
to say that if you cannot find the data sheet for the particular
manufacturer that you have chips for, then finding a data sheet for an
equivalent chip from another manufacturer will give this figure accurately
enough for your purpose.

Depending on just what you are wanting to do, you may find it advantageous
to have external refresh hardware as it will take a reasonable number of
cycles of PIC processing to handle a timer interrupt to do the refresh.

--
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


More... (looser matching)
- Last day of these posts
- In 2002 , 2003 only
- Today
- New search...