NT5CB256M8FN datasheet(21/163 Pages) NANYA

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DDR3(L) 2Gb SDRAM

NT5CB(C)256M8FN / NT5CB(C)128M16FP

Version 1.7

Nanya Technology Cooperation ©

04/2015

DLL Enable/Disable

The DLL must be enabled for normal operation. DLL enable is required during power up initialization, and upon returning to

normal operation after having the DLL disabled. During normal operation (DLL-on) with MR1 (A0=0), the DLL is

automatically disabled when entering Self-Refresh operation and is automatically re-enable upon exit of Self-Refresh

operation. Any time the DLL is enabled and subsequently reset, tDLLK clock cycles must occur before a Read or

synchronous ODT command can be issued to allow time for the internal clock to be synchronized with the external clock.

Failing to wait for synchronization to occur may result in a violation of the tDQSCK, tAON, or tAOF parameters. During

tDLLK, CKE must continuously be registered high. DDR3(L) SDRAM does not require DLL for any Write operation, expect

when RTT_WR is enabled and the DLL is required for proper ODT operation. For more detailed information on DLL Disable

operation in DLL-off Mode.

The direct ODT feature is not supported during DLL-off mode. The on-die termination resistors must be disabled by continu-

ously registering the ODT pin low and/or by programming the RTT_Nom bits MR1{A9,A6,A2} to {0,0,0} via a mode register

set command during DLL-off mode.

The dynamic ODT feature is not supported at DLL-off mode. User must use MRS command to set Rtt_WR, MR2 {A10, A9}

= {0, 0}, to disable Dynamic ODT externally.

Output Driver Impedance Control

The output driver impedance of the DDR3(L) SDRAM device is selected by MR1 (bit A1 and A5) as shown in MR1 definition

figure.

ODT Rtt Values

DDR3(L) SDRAM is capable of providing two different termination values (Rtt_Nom and Rtt_WR). The nominal termination

value Rtt_Nom is programmable in MR1. A separate value (Rtt_WR) may be programmable in MR2 to enable a unique Rtt

value when ODT is enabled during writes. The Rtt_WR value can be applied during writes even when Rtt_Nom is disabled.

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