sdram control register

Hi all,

 Does anyone know how to enable the bit "mode_en" in SDRAM Control
Register (MBAR + 0x0104) ... I have been struggling for that .. 

Just briefly about this register..

writing is not allowed to this register when mode_en bit = '0',

to unlock it we should write mode_en = '1', trying to do this directly
makes the core restart , i think this should be enabled VIA some command
or s0mething.. any help please ...


Thanks for the reply in Advance ..
        nSr