Unbuffered SDRAM [forwarded from Soban]

Salaam All,


PC Unbuffered SDRAM DIMM Specs specify many things like mechanical 
parameters, PCB track information...etc

But things important for us are:
The organisation of the SDRAM,configuration (how the SDRAMs are 
interconnected).

The SOPC mentions that it supports PC Unbuffered SDRAM DIMM 
Specification configurations 8 and 9.

In the PC SDRAM Unbuffered DIMM specs the configuration 8 and 9 
will give you following information.
(You'll find the specs at  
www.intel.com/technology/memory/UNB_001.htm )

+--------+-------------------------------------------------------
 
|Cfg#|DIMM  DIMM    SDRAM    SDRAM  # of    #Rows of # Banks in
|    |Capty Orgzn   density  Orgzn  SDRAMs  SDRAM      SDRAM
+----------------------------------------------------------------
 
|8   |64 MB 8M X 64  64 Mbit 4MX16  8       2          4
|9   |64 MB 8M X 64  64 Mbit  8MX8  8       1          4
+----+-----------------------------------------------------------
 

----+----------------+
Cfg#|# Address bits  |
     |  row/bank/col| |
----+----------------+
   8 |   12/2/8       |
   9 |   12/2/9       |
----+----------------+


And the block diagram for these configurations is also given.
I have drawn one of the pairs of Configuration #8.
similiarly there are 3 more pairs of SDRAMs for data lines 
(16-31), (32-47) and (48-63)

Here point to note is that both the SDRAMs are connected to same 
data lines and Data mask lines but diffe
erent Chip selects.

I hope now there is no confusion on the No.of Address lines and 
the memory size.
                              cs0        cs1
                               |           |
                             __|__       __|__
                     16     |     | 16  |     |
    (0-15) data -----/----->|     |--/->|     |
                            |     |     |     |
        data mask----/----->|  1  |---->| 2   |
                            |     |     |     |
                            |     |     |     |
                            |_____|     |_____|

We need to know which SDRAM DIMM is actually there on the SOPC 
board(I mean the device number and Vendor), bcoz many SDRAM DIMM 
will come under these specs and the specs don't tell anything 
about the timing and operation, commands which are important for 
us.



Also I agree with Jameel,SDRAM needs to be inintialised. 
Moreover,
many of them also have powerOn sequence.

Hope it helps.

Regards,
-Soban.



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