SDRAM
Austin Semiconductor, Inc.
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.
The ordering of accesses within a burst is determined
by the burst length, the burst type and the starting column
address, as shown in Table 1.
Burst
Length
2
AS4SD4M16
Table 1
BURST DEFINITION
Starting Column
Address
A0
0
1
A0
A1
0
0
0
1
1
0
1
1
A0
A2
A1
0
0
0
0
0
1
0
1
0
0
1
1
1
0
0
1
0
1
1
1
0
1
1
1
n = A0 - A9
location 0 - y
Order of Access Within a Burst
Type = Sequential Type = Interleaved
0-1
1-0
0,1,2,3
1,2,3,0
2,3,0,1
3,0,1,2
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
Cn, Cn+1, Cn+2,
Cn+3, Cn+4…
…Cn-1,
Cn…
0-1
1-0
0,1,2,3
1,0,3,2
2,3,0,1
3,2,1,0
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
Not Supported
4
8
Full Page
(y)
A11
A10
A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
Address Bus
Mode Register(Mx)
11
10
Reserved*
9
WB
8
7
Op Mode
6
5
4
CAS Latency
3
BT
2
1
0
Burst Length
* Should program M11,
M10=0,0 to ensure
compatibility with future
devices.
M2
0
0
0
0
1
1
1
1
M1
0
0
1
1
0
0
1
1
M0
0
1
0
1
0
1
0
1
Burst Length
M3=0
M3=1
1
1
2
2
4
4
8
8
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Full Page
Reserved
M3
0
1
Burst Type
Sequential
Interleave
M6
0
0
0
0
1
1
1
1
M5
0
0
1
1
0
0
1
1
M4
0
1
0
1
0
1
0
1
CAS Latency
Reserved
Reserved
2
3
Reserved
Reserved
Reserved
Reserved
M8
0
-
M7
0
-
M6 - M0
Defined
-
Operating Mode
Standard Operation
All other states reserved
M9
0
1
Write Burst Mode
Programmed Burst Length
Single Location Access
FIGURE 1
MODE REGISTER DEFINITION
NOTE:
1. For full-page accesses: y = 256 (x16).
2. For a burst length of two, A1-A7 (x16)
select the block-of-two burst; A0 selects
the starting column within the block.
3. For a burst length of four, A2-A7 (x16)
select the block-of-four burst; A0-A1
select the starting column within the
block.
4. For a burst length of eight, A3-A7 (x16)
select the clock-of-eight burst; A0-A2
select the starting column within the
block.
5. For a full-page burst, the full row is
selected and A0-A7 (x16) select the
starting column.
6. Whenever a boundary of the block is
reached within a given sequence above,
the following access wraps within the
block.
7. For a burst length of one, A0-A7 (x16)
select the unique column to be accessed,
and Mode Register bit M3 is ignored.
AS4SD4M16
Rev. 1.5 10/01
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
7
AUSTIN [ AUSTIN SEMICONDUCTOR ]
