IS42S81600D, IS42S16800D
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 512 columns by 16 bits or 4,096 rows by 1,024
columns by 8 bits.
The128MSDRAMisinitializedafterthepowerisappliedto
VDD and VDDQ (simultaneously) and the clock is stable with
DQM High and CKE High.
A 100µs 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
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)
.
TheaddressbitsA0-A9 (x8);A0-A8(x16)registeredcoincident
with the READ or WRITE command are used to select the
starting column location for the burst access.
The mode register should be loaded prior to applying any
operational command because it will power up in an un-
known 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
Rev. E
07/28/08
ISSI [ INTEGRATED SILICON SOLUTION, INC ]
