®
IS42S32400B
ISSI
Initialization
FUNCTIONAL DESCRIPTION
SDRAMs must be powered up and initialized in a
predefinedmanner.
The128MbSDRAMsarequad-bankDRAMswhichoperate
at3.3Vandincludeasynchronousinterface(allsignalsare
registered on the positive edge of the clock signal, CLK).
Each of the 33,554,432-bit banks is organized as 4,096
rows by 256 columns by 32 bits.
The128MSDRAMisinitializedafterthepowerisappliedto
VDD and VDDQ (simultaneously) and the clock is stable with
DQM High and CKE High.
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
A 100µs delay is required prior to issuing any command
other than a COMMAND INHIBIT or aNOP. The COMMAND
INHIBITorNOPmaybeappliedduringthe100µsperiodand
should continue at least through the end of the period.
With at least one COMMAND INHIBIT or NOP command
havingbeenapplied,aPRECHARGEcommandshouldbe
appliedoncethe100µsdelayhasbeensatisfied. Allbanks
mustbeprecharged. Thiswillleaveallbanksinanidlestate
after which at least two AUTO REFRESH cycles must be
performed. After the AUTO REFRESH cycles are complete,
the SDRAM is then ready for mode register programming.
beaccessed(BA0andBA1selectthebank,A0-A11selecttherow)
.
The address bits A0-A7 registered coincident with the READ
orWRITEcommandareusedtoselectthestartingcolumn
location for the burst access.
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.
The mode register should be loaded prior to applying any
operational command because it will power up in an un-
known state.
Integrated Silicon Solution, Inc. — www.issi.com — 1-800-379-4774
19
PRELIMINARYINFORMATION Rev. 00G
06/15/06
ISSI [ INTEGRATED SILICON SOLUTION, INC ]
