40 Integrated Silicon Solution, Inc. — www.issi.com
Rev. B
05/12/2015
IS42/45R86400D/16320D/32160D, IS42/45S86400D/16320D/32160D
CLK
CKE
HIGH
COLUMN ADDRESS
AUTO PRECHARGE
BANK ADDRESS
CS
RAS
CAS
WE
A0-A9, A11
A10
BA0, BA1
NO PRECHARGE
A12
WRITE COMMAND
Thestartingcolumnandbankaddressesareprovidedwith
theWRITEcommand,andautoprechargeiseitherenabled
or disabled for that access. If auto precharge is enabled,
the row being accessed is precharged at the completion of
theburst.ForthegenericWRITEcommandsusedinthe
following illustrations, auto precharge is disabled.
DuringWRITEbursts,therstvalid
data-in
element will be
registered coincident
with the
WRITE
command.
Subsequent
data elements will be registered on each successive posi-
tiveclockedge.Uponcompletionofaxed-lengthburst,
assuming no other commands have been initiated, the
DQs will remain High-Z and any additional input data will
beignored(seeWRITEBurst).Afull-pageburstwillcon-
tinue until terminated. (At the end of the page, it will wrap
to column 0 and continue.)
DataforanyWRITEburstmaybetruncatedwithasubse-
quentWRITEcommand,anddataforaxed-lengthWRITE
burst may be immediately followed by data for a WRITE
command. The new WRITE command can be issued on
anyclockfollowingthepreviousWRITEcommand,andthe
data provided coincident with the new command applies to
the new command.
AnexampleisshowninWRITEtoWRITEdiagram.Data
n + 1 is either the last of a burst of two or the last desired
ofalongerburst.The512MbSDRAMusesapipelined
architecture and therefore does not require the 2n rule as-
sociatedwithaprefetcharchitecture.AWRITEcommand
can be initiated on any clock cycle following a previous
WRITEcommand.Full-speedrandomwriteaccesseswithin
a page can be performed to the same bank, as shown in
RandomWRITECycles,oreachsubsequentWRITEmay
be performed to a different bank.
DataforanyWRITEburstmaybetruncatedwithasubse-
quentREADcommand,anddataforaxed-lengthWRITE
burst may be immediately followed by a subsequent READ
command.OncetheREADcommandisregistered,the
datainputswillbeignored,andWRITEswillnotbeex-
ecuted.AnexampleisshowninWRITEtoREAD.Datan
+ 1 is either the last of a burst of two or the last desired
of a longer burst.
Data for a xed-length WRITE burst may be followed
by,ortruncatedwith,aPRECHARGEcommand tothe
same bank (provided that auto precharge was not acti-
vated), and a full-page WRITE burst may be truncated
withaPRECHARGE command tothesame bank.The
PRECHARGEcommandshouldbeissuedtdpl after the
clock edge at which the last desired input data element
isregistered.Theautoprechargemoderequiresatdpl of
at least one clock plus time, regardless of frequency. In
addition,whentruncatingaWRITEburst,theDQMsignal
must be used to mask input data for the clock edge prior
to,andtheclockedgecoincidentwith,thePRECHARGE
command.AnexampleisshownintheWRITEtoPRE-
CHARGEdiagram.Datan+1 is either the last of a burst
oftwoorthelastdesiredofalongerburst.Followingthe
PRECHARGEcommand,asubsequentcommandtothe
same bank cannot be issued until trp is met.
In the case of a fixed-length burst being executed to comple-
tion, a PRECHARGE command issued at the optimum
time
(as described above)
provides the same operation that
would result from the same fixed-length burst with auto
precharge.Thedisadvantageofthe
PRECHARGE
command
is that it requires that the command and address buses be
available at the appropriate time to issue the command; the
advantageofthePRECHARGEcommandisthatitcanbe
used to truncate fixed-length or full-page bursts.
Fixed-lengthorfull-pageWRITEburstscanbetruncated
withtheBURSTTERMINATEcommand.Whentruncat-
ingaWRITEburst,theinputdataappliedcoincidentwith
theBURSTTERMINATEcommandwillbeignored.The
lastdatawritten(providedthatDQMisLOWatthattime)
will be the input data applied one clock previous to the
BURSTTERMINATEcommand.ThisisshowninWRITE
BurstTermination,wheredatan is the last desired data
element of a longer burst.
WRITES
WRITEburstsareinitiatedwithaWRITEcommand,as
showninWRITECommanddiagram.
Note:
x32: A9 and A11 are "Don't Care"
x16: A11 is "Don't Care"