IS42S81600D, IS42S16800D
BURST LENGTH
ReadandwriteaccessestotheSDRAMareburstoriented,
with the burst length being programmable, as shown in
MODE REGISTER DEFINITION. The burst length deter-
mines the maximum number of column locations that can
be accessed for a given READ or WRITE command. Burst
lengths of 1, 2, 4 or 8 locations are available for both the
sequential and the interleaved burst types, and a full-page
burstisavailableforthesequentialtype.Thefull-pageburst
is used in conjunction with the BURST TERMINATE com-
mand to generate arbitrary burst lengths.
ing that the burst will wrap within the block if a boundary is
reached. The block is uniquely selected by A1-A8 (x16)
whentheburstlengthissettotwo;byA2-A8(x16)whenthe
burstlengthissettofour;andbyA3-A8(x16)whentheburst
length is set to eight. The remaining (least significant)
address bit(s) is (are) used to select the starting location
withintheblock.Full-pageburstswrapwithinthepageifthe
boundary is reached.
Burst Type
Accesses within a given burst may be programmed to be
either sequential or interleaved; this is referred to as the
burst type and is selected via bit M3.
Reservedstatesshouldnotbeused,asunknownoperation
or incompatibility with future versions may result.
When a READ or WRITE command is issued, a block of
columnsequaltotheburstlengthiseffectivelyselected.All
accesses for that burst take place within this block, mean-
Theorderingofaccesseswithinaburstisdeterminedbythe
burstlength,thebursttypeandthestartingcolumnaddress,
as shown in BURST DEFINITION table.
BURST DEFINITION
Burst
StartingColumn
Address
OrderofAccessesWithinaBurst
Length
Type=Sequential
Type=Interleaved
A 0
2
4
0
1
0-1
1-0
0-1
1-0
A 1
0
A 0
0
0-1-2-3
1-2-3-0
2-3-0-1
3-0-1-2
0-1-2-3
1-0-3-2
2-3-0-1
3-2-1-0
0
1
1
0
1
1
A 2
A 1
0
A 0
0
0
0-1-2-3-4-5-6-7
1-2-3-4-5-6-7-0
2-3-4-5-6-7-0-1
3-4-5-6-7-0-1-2
4-5-6-7-0-1-2-3
5-6-7-0-1-2-3-4
6-7-0-1-2-3-4-5
7-0-1-2-3-4-5-6
0-1-2-3-4-5-6-7
1-0-3-2-5-4-7-6
2-3-0-1-6-7-4-5
3-2-1-0-7-6-5-4
4-5-6-7-0-1-2-3
5-4-7-6-1-0-3-2
6-7-4-5-2-3-0-1
7-6-5-4-3-2-1-0
NotSupported
0
0
1
0
1
0
8
0
1
1
1
0
0
1
0
1
1
1
1
0
1
1
Full
Page
(y)
n=A0-A7
Cn, Cn + 1, Cn + 2
Cn + 3, Cn + 4...
…Cn-1,
(location0-y)
Cn…
Integrated Silicon Solution, Inc. — www.issi.com
25
Rev. E
07/28/08
ISSI [ INTEGRATED SILICON SOLUTION, INC ]
