42

Rev. 0A | October 2022

www.issi.com - dram@issi.com

IS43/46LR32320C

IS43/46LR16640C

Figure34 : Self refresh

Self refresh

This state retains data in the Mobile DDR, even if the rest of the system is powered down (even without external clocking). Note refresh

interval timing while in Self Refresh mode is scheduled internally in the Mobile DDR and may vary and may not meet tREFI time. "Don't

Care" except CKE, which must remain low. An internal refresh cycle is scheduled on Self Refresh entry. The procedure for exiting Self

Refresh mode requires a series of commands. First clock must be stable before CKE going high. NOP commands should be issued for the

duration of the refresh exit time (tXSR), because time is required for the completion of any internal refresh in progress. The use of SELF

REFRESH mode introduces the possibility that an internally timed event can be missed when CKE is raised for exit from self refresh mode.

Figure33 : Auto refresh

Auto refresh

The Auto refresh command is used during normal operation of the Mobile DDR. It is non persistent, so must be issued each time a refresh

is required. The refresh addressing is generated by the internal refresh controller. The Mobile DDR requires AUTO REFRESH commands at an

average periodic interval of tREFI. To allow for improved efficiency in scheduling and switching between tasks, some flexibility in the

absolute refresh interval is provided. A maximum of eight AUTO REFRESH commands can be posted to any given Mobile DDR, and the

maximum absolute interval between any AUTO REFRESH command and the next AUTO REFRESH command is 8*tREFI.

AREF

NOP

NOP

NOP

AREF

PCG

NOP

/CLK

CLK

CKE

T0

Command

T1

T3

tCH

tCL

DQS, DQ, DM

Tb0

tIS

tIH

A10

tCK

T2

T4

Ta0

tRP

Don’t care

VALID

A0~A9, A11-A13

All Banks

One Bank

BA

BA0, BA1

ACT

NOP

Tb0

RA

Ta2

BA

RA

NOP

VALID

tRFC

tRFC

tIS

tIH

VALID

NOP

AREF

NOP

/CLK

CLK

CKE

T0

Command

T1

Ta0

DQS, DQ, DM

Tb0

tIS

tIH

Ta1

tRP

Don’t care

Address

tXSR

tIS

tIH

tIS

tIS

VALID

Self-refresh mode entry

Self-refresh mode exit