trouble interfacing 16MB SDRAM to AT91RM9200 :-(

Hi everyone,

ive been trying to interface a 16MB SDRAM (MT84LC8M16A2, 128Mbit,
2x16x4)with an AT91RM9200 con my custom board. As u might have guessed,
its not working. Ive checked and rechecked the continuity of all
connections, they seem to be okay. The SDRAM and the uC are placed
close to each other on the PCB (which me and my friend designed). The
following is the list of connections, please tell me if u think theyr
ok:

16-bit data bus (configured by writing 0x10 in the SDRAM controller`s
mode register on the uC)

uC`s pins           Pins on the SDRAM
----------          -----------------
A2-A11                A0-A9
SDA10                 A10
A16-A17(BA0-BA1)      BA0-BA1
SDCKE                 CKE
SDCK                  CLK
A0/NBS0               DQML
NBS1                  DQMH
CAS                   -CAS
RAS                   -RAS
SDWE                  -WE
SDCS                  -CS
D0-D15                DQ0-DQ15

two 1uf electrolytic and 0.1uf ceramic capacitor pairs are connected in
parallel between VDD and GND and VDDQ and GND.

Im at my wits end with this one, if anyone here has links to places
that carry a schematic or something of the same, kindly point me to
them. Its my senior undergrad project :-(

Thanx in anticipation,
Mayank

"Mayank Kaushik" <prehistorictoad2k@yahoo.com> wrote in message 
news:1114966918.124691.189630@f14g2000cwb.googlegroups.com...
> Hi everyone,
>
> ive been trying to interface a 16MB SDRAM (MT84LC8M16A2, 128Mbit,
> 2x16x4)with an AT91RM9200 con my custom board. As u might have guessed,
> its not working.

[SNIP]

> Im at my wits end with this one, if anyone here has links to places
> that carry a schematic or something of the same, kindly point me to
> them. Its my senior undergrad project :-(
>
> Thanx in anticipation,
> Mayank

Care to tell what the symptoms of 'not working' are? Can you store any data 
at all? Do you experience data corruption? Have you determined if there are 
bit- or address- faults? Did you properly initialize the SDRAM control 
registers to match your device? And last but not least, have you ruled out a 
faulty SDRAM chip?

Rob

On 2005-05-01, Mayank Kaushik <prehistorictoad2k@yahoo.com> wrote:
> 16-bit data bus (configured by writing 0x10 in the SDRAM controller`s
> mode register on the uC)
>
> uC`s pins           Pins on the SDRAM
> ----------          -----------------
> A2-A11                A0-A9
> SDA10                 A10
> A16-A17(BA0-BA1)      BA0-BA1
> SDCKE                 CKE
> SDCK                  CLK
> A0/NBS0               DQML
> NBS1                  DQMH
> CAS                   -CAS
> RAS                   -RAS
> SDWE                  -WE
> SDCS                  -CS
> D0-D15                DQ0-DQ15

These look exactly as one of our designs - except that you don't mention
A11 of the SDRAM chip.  Our design has two chips (for a 32-bit data bus)
though - I haven't checked if that affects the connections of the lower
SDRAM chip.

Do you configure the SDRAM controller and chip select properly in your
software?  I remember it wasn't a trivial task..

Also, your 1 &#4294967295;F electrolytic + 0.1 &#4294967295;F cerco doesn't sound too good -
we have 7 x 100 nF for each SDRAM chip on a 6-layer PCB.

  -jm

Rob Turk wrote:
> Care to tell what the symptoms of 'not working' are? Can you store
any data
> at all? Do you experience data corruption? Have you determined if
there are
> bit- or address- faults?

Whoops, i forgot to write that.
I tested it by writing 0s at all locations inside the chip, and then
reading them out. but i get 0xff at ALL locations..no data corruption,
just 0xff everywhere. i tried writing other values too, but all i got
was 0xff everywhere.

> Did you properly initialize the SDRAM control
> registers to match your device?
Yeah, i did..copied values from application notes on Atmel`s site, when
that didnt work, calculated values from the SDRAM`s datasheet. Didnt
work.

> And last but not least, have you ruled out a
> faulty SDRAM chip?
I think il blame it on the chip when every other attempt fails. Im also
concerned about the pin connections, if someone could veriy them..they
seem fine to me, but a second opinion is invited.


Thanx in anticipation,
Mayank

Hi,

> A11 of the SDRAM chip.
Sorry i forgot, its connected to A13 of the At91.
A1, NBS2, NBS3 (on the uC)have no-connection (they would be connected
on the 2nd chip in your 32-bit design)

> Our design has two chips (for a 32-bit data bus)
> though - I haven't checked if that affects the connections of the
lower
> SDRAM chip.

Could you please tell me what would be the difference in setting up a
32-bit data bus and a 16-bit bus? I think just the mode register (MR)
of the SDRAM controller on the uC needs to be altered.


> Do you configure the SDRAM controller and chip select properly in
your
> software?  I remember it wasn't a trivial task..
Yes, ive done that.


> Also, your 1 =B5F electrolytic + 0.1 =B5F cerco doesn't sound too good
-
> we have 7 x 100 nF for each SDRAM chip on a 6-layer PCB.
Mine is a 2 layer PCB..4 caps for the SDRAM: two 100nf ceramics and two
1uF electrolytics.

Thanks,
Mayank

Hi guys, i replaced the SDRAM chip, it seemed to work..but now i have
another problem, im pasting it under a new topic.