IS42S81600D, IS42S16800D
GENERAL DESCRIPTION
READ
The READ command selects the bank from BA0, BA1
inputs and starts a burst read access to an active row.
InputsA0-A9(x8);A0-A8(x16)providesthestartingcolumn
location. WhenA10isHIGH,thiscommandfunctionsasan
AUTOPRECHARGEcommand. Whentheautoprecharge
is selected, the row being accessed will be precharged at
the end of the READ burst. The row will remain open for
subsequent accesses when AUTO PRECHARGE is not
selected. DQ’sreaddataissubjectto thelogiclevel onthe
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-A9
(x8); A0-A8 (x16). Whether or not AUTO-PRECHARGE is
used is determined 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,
thenextcommandfortheselectedbank(s)isexecutedafter
passage of the period tRP, which is the period required for
bankprecharging. Onceabankhasbeenprecharged,itis
intheidlestateandmustbeactivatedpriortoanyREADor
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.
ACTIVE COMMAND
When the ACTIVE COMMAND is activated, BA0, BA1
inputs selects a bank to be accessed, and the address
inputs on A0-A11 selects the row. Until a PRECHARGE
command is issued to the bank, the row remains open for
accesses.
AUTO PRECHARGE
TheAUTOPRECHARGEfunctionensuresthattheprecharge
is initiated at the earliest valid stage within a burst. This
functionallowsforindividual-bankprechargewithoutrequir-
ing an explicit command. A10 to enable the AUTO
Integrated Silicon Solution, Inc. — www.issi.com
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Rev. E
07/28/08
ISSI [ INTEGRATED SILICON SOLUTION, INC ]
