®
IS42S81600A, IS42S16800A, IS42S32400A
IS42LS81600A, IS42LS16800A, IS42LS32400A
ISSI
GENERAL DESCRIPTION
READ
The READ command selects the bank from BA0, BA1
inputs and starts a burst read access to an active row.
Inputs A0-A7 provides the starting column location. When
A10 is HIGH, this command functions as an AUTO
PRECHARGE command. When the auto precharge is
selected, therowbeingaccessedwillbeprechargedatthe
end of the READ burst. The row will remain open for
subsequent accesses when AUTO PRECHARGE is not
selected. DQ’s read data is subject to the logic level on the
DQM inputs two clocks earlier. When a given DQM signal
wasregisteredHIGH,thecorrespondingDQ’swillbeHigh-
Z two clocks later. DQ’s will provide valid data when the
DQM signal was registered LOW.
PRECHARGEfunctioninconjunctionwithaspecificREAD
orWRITEcommand. ForeachindividualREADorWRITE
command, auto precharge is either enabled or disabled.
AUTO PRECHARGE does not apply except in full-page
burstmode.UponcompletionoftheREADorWRITEburst,
a precharge of the bank/row that is addressed is automati-
callyperformed.
AUTO REFRESH COMMAND
This command executes the AUTO REFRESH operation.
The row address and bank to be refreshed are automatically
generatedduringthisoperation. Thestipulatedperiod(tRC)is
required for a single refresh operation, and no other com-
mandscanbeexecutedduringthisperiod. Thiscommandis
executed at least 4096 times for every 64ms. During an
AUTOREFRESHcommand,addressbitsare“Don’tCare”.
This command corresponds to CBR Auto-refresh.
WRITE
A burst write access to an active row is initiated with the
WRITE command. BA0, BA1 inputs selects the bank, and
the starting column location is provided by inputs A0-A7.
WhetherornotAUTO-PRECHARGEisusedisdetermined
by A10.
BURST TERMINATE
TheBURSTTERMINATEcommandforciblyterminatesthe
burst read and write operations by truncating either fixed-
length or full-page bursts and the most recently registered
READ or WRITE command prior to the BURST TERMI-
NATE.
Therowbeingaccessedwillbeprechargedattheendofthe
WRITE burst, if AUTO PRECHARGE is selected. If AUTO
PRECHARGE is not selected, the row will remain open for
subsequent accesses.
Amemoryarrayiswrittenwithcorrespondinginputdataon
DQ’sandDQMinputlogiclevelappearingatthesametime.
Data will be written to memory when DQM signal is LOW.
When DQM is HIGH, the corresponding data inputs will be
ignored, and a WRITE will not be executed to that byte/
column location.
COMMAND INHIBIT
COMMAND INHIBIT prevents new commands from being
executed. Operations in progress are not affected, apart
from whether the CLK signal is enabled
NO OPERATION
When CS is low, the NOP command prevents unwanted
commandsfrombeingregisteredduringidleorwaitstates.
PRECHARGE
ThePRECHARGEcommandisusedtodeactivatetheopen
row in a particular bank or the open row in all banks. BA0,
BA1canbeusedtoselectwhichbankisprechargedorthey
aretreatedas“Don’tCare”. A10determinedwhetheroneor
all banks are precharged. After executing this command,
the next command for the selected banks(s) is executed
afterpassageoftheperiodtRP, whichistheperiodrequired
for bank precharging. Once a bank has been precharged,
itisintheidlestateandmustbeactivatedpriortoanyREAD
or WRITE commands being issued to that bank.
LOAD MODE REGISTER
During the LOAD MODE REGISTER command the mode
registerisloadedfromA0-A11. Thiscommandcanonlybe
issued when all banks are idle.
EXTENDED MODE REGISTER
The extended mode register defines low power functions.
During this command A0-A11 are data input pins. After
power on, the extended mode register set command must
be executed to fix low power functions. During tRSC
following this command, they can not accept any other
command.
AUTO PRECHARGE
TheAUTOPRECHARGEfunctionensuresthattheprecharge
is initiated at the earliest valid stage within a burst. This
functionallowsforindividual-bankprechargewithoutrequir-
ing an explicit command. A10 to enables the AUTO
Integrated Silicon Solution, Inc. — www.issi.com — 1-800-379-4774
ADVANCEDINFORMATION Rev. 00A
9
06/01/02
ICSI [ INTEGRATED CIRCUIT SOLUTION INC ]
