IS46DR16640C datasheet(33/49 Pages) ISSI

33 / 49 page

Integrated Silicon Solution, Inc. — www.issi.com

Rev. 00A

6/4/2013

IS43/46DR81280C, IS43/46DR16640C

Power-up and Initialization Sequence (cont'd)

f) Issue an EMRS command to EMR(3).

g) Issue EMRS to enable DLL.

h) Issue a Mode Register Set command for DLL reset.

i) Issue a precharge all command.

j) Issue 2 or more auto-refresh commands.

k) Issue a MRS command with LOW to A8 to initialize device operation. (i.e. to program operating parameters without

resetting the DLL.)

l) At least 200 clocks after step h, execute OCD Calibration. This is done by EMRS to EMR(1) to set OCD Calibration

Default (A9=A8=A7=HIGH) followed by EMRS to EMR(1) to exit OCD Calibration Mode (A9=A8=A7=LOW) must be

issued with other operating parameters of EMR(1).

m) The DDR2 SDRAM is now ready for normal operation.

Initialization Sequence after Power-Up

/CK

CKE

Command

PRE

ALL

PRE

ALL

EMRS

MRSREF

REF

MRSEMRS

EMRS

ANY

CMD

DLL

ENABLE

DLL

RESET

OCD

Default

OCD

CAL. MODE

EXIT

Follow OCD

Flowchart

400ns

tRFC

tRP

tMRD

tOIT

min 200 Cycle

NOP

ODT

tCL

tCH

tIS

Programming the Mode and Extended Mode Registers

For application flexibility, burst length, burst type, CAS latency, DLL reset function, write recovery time (WR) are user

defined variables and must be programmed with a Mode Register Set (MRS) command. Additionally, DLL disable

function, driver impedance, additive CAS latency, ODT (On Die Termination), single-ended strobe, and OCD (off chip

driver impedance adjustment) are also user defined variables and must be programmed with an Extended Mode

executing the MRS or EMRS Commands. Even if the user chooses to modify only a subset of the MR, or EMR(1),

EMR(2), or EMR(3) variables, all variables within the addressed register must be redefined when the MRS or EMRS

commands are issued.

MRS, EMRS and Reset DLL do not affect memory array contents, which means re-initialization including those can be

executed at any time after power-up without affecting memory array contents.

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