®
IS42S81600A, IS42S16800A, IS42S32400A
IS42LS81600A, IS42LS16800A, IS42LS32400A
ISSI
Initialization
FUNCTIONAL DESCRIPTION
SDRAMs must be powered up and initialized in a
predefinedmanner.
The128MbSDRAMsarequad-bankDRAMswhichoperate
at 2.5V or 3.3V and include a synchronous interface (all
signals are registered on the positive edge of the clock
signal,CLK).Eachofthe16,777,216-bitbanksisorganized
as 4,096 rows by 256 columns by 16 bits.
The128MSDRAMisinitializedafterthepowerisappliedto
VDD and Vddq (simultaneously) and the clock is stable.
A 200µs delay is required prior to issuing any command
other than a COMMAND INHIBIT or aNOP. The COMMAND
INHIBITorNOPmaybeappliedduringthe100usperiodand
should continue at least through the end of the period.
Read and write accesses to the SDRAM are burst oriented;
accesses start at a selected location and continue for a
programmed number of locations in a programmed
sequence. Accesses begin with the registration of an AC-
TIVEcommandwhichisthenfollowedbyaREADorWRITE
command. The address bits registered coincident with the
ACTIVE command are used to select the bank and row to
With at least one COMMAND INHIBIT or NOP command
havingbeenapplied,aPRECHARGEcommandshouldbe
appliedoncethe100µsdelayhasbeensatisfied. Allbanks
mustbeprecharged. Thiswillleaveallbanksinanidlestate
wheretwoAUTOREFRESHcyclesmustbeperformed. After
theAUTOREFRESHcyclesarecomplete,theSRDRAMisthen
readyformoderegisterprogramming.
beaccessed(BA0andBA1selectthebank,A0-A11selecttherow)
.
Theaddressbits(A0-A7)registeredcoincidentwiththeREAD
orWRITEcommandareusedtoselectthestartingcolumn
location for the burst access.
Themoderegisterandextendedmoderegistersshouldbe
loadedpriortoapplyinganyoperationalcommandbecause
it will power up in an unknown state.
Prior to normal operation, the SDRAM must be initialized.
The following sections provide detailed information covering
device initialization, register definition, command
descriptions and device operation.
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Integrated Silicon Solution, Inc. — www.issi.com — 1-800-379-4774
ADVANCEDINFORMATION Rev. 00A
06/01/02
ICSI [ INTEGRATED CIRCUIT SOLUTION INC ]
