DDR SDRAM Initialization.

sivakumar sivakumar.subramani at wipro.com
Mon Jan 13 08:45:00 CET 2003


Thanks for the information.

I have gone through the code and have following query.
Following is the one of the step in Initialization of DDR SDRAM.

-Next a MODE REGISTER SET command should be issued for the Extended
 Mode Register to enable the DLL,

        /* 5. Issue EMRS to enable DLL */
        SET_RAM_COMMAND(RAM_COMMAND_EMRS)
        movl (0x0000<<MD_SHIFT), %eax
        DO_DELAY

First we are setting the Mode select bit of DRAM controller Mode
Register to Extended Mode Register Set Enable. 

>From DDR spec, it is given that zero bit of EMRS will enable the DLL.

Here I want to know how by moving the (0x0000 << MD_SHIFT) to eax
register, we are writting to Extended mode register.

Can any one explain this?

Thanks,
Siva

On Mon, 2003-01-13 at 05:07, Ronald G. Minnich wrote:
> On 12 Jan 2003, sivakumar wrote:
> 
> > I want to support DDR SDRAM in linuxbios. When was browsing the code, I
> > found only the SDRAM support. Also  I found from the specification that
> > Initialization sequence of DDR SDRAM and SDRAM are different.
> 
> DDR is in there, see the 7500 port.
> 
> kron
-- 
sivakumar <sivakumar.subramani at wipro.com>
wipro




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