SDRAM Controller
8-11
GMS30C7201 Data Sheet
8.6
SDRAM Memory Map
The SDRAM controller can interface with up to four SDRAMs. Three SDRAM sizes are
supported
—
16, 64 and 128Mbits
—
which may be organized in either two or four banks
but which must have a 16-bit data bus. A maximum of 64Mbytes of memory may be
addressed by the SDRAM controller, which is subdivided into four 16Mbyte blocks, one
for each of the external SDRAMs.
The mapping of the AMBA address bus to the SDRAM row and column addresses is
given in
Table 8-8: SDRAM row/column address map
. The first row of the diagram
indicates the SDRAM address bit (A[13:0]); the remaining numbers indicate the AMBA
address bits MBA[23:1]. Note that for 16Mbit devices, pins A[11,9] on the SDRAM
should be connected to pins A[13,12] on the GMS30C7201, and the pins A[11,9]
should not be connected.
Notes
(1) For the 16Mbit device, SDRAM address line A11 should be connected to the
GMS30C7201 pin SA[13](BS0), and the SDRAM address line A9 should be connected
to the GMS30C7201 pin SA[12](BS1). The GMS30C7201 address lines A11 and A9
should not be connected.
(2) Since all burst accesses commence on a word boundary, and SDRAM addresses
are non-incrementing (the address incrementer is internal to the device), column
address zero will always be driven to logic ‘0’.
*
An asterisk denotes the address lines that are used by the SDRAM.
The start addresses of each SDRAM is fixed to a 16Mbyte boundary. The memory
management unit will be used to map the actual banks that exist into contiguous
memory as seen by the ARM. Bits [25:24] of the AMBA address bus select the device
to be initialized, as described in
Table 8-9: SDRAM device selection
on page 8-12.
SDRAM
ADDR
13
(BS0)
12
(BS1)
11
10
9
8
7
6
5
4
3
2
1
0
Row 16Mbit
Device
10
*
9
*
Note
1
20
*
Note
1
19
*
18
*
17
*
16
*
15
*
14
*
13
*
12
*
11
*
Col 16Mbit
Device
10
9
Note
1
20
Note
1
23
8
*
7
*
6
*
5
*
4
*
3
*
2
*
Note
2
Row 64Mbit
Device
10
*
9
*
22
*
20
*
21
*
19
*
18
*
17
*
16
*
15
*
14
*
13
*
12
*
11
*
Col 64Mbit
Device
10
9
22
20
21
23
8
*
7
*
6
*
5
*
4
*
3
*
2
*
Note
2
Row
128Mbit
Device
10
*
9
*
22
*
20
*
21
*
19
*
18
*
17
*
16
*
15
*
14
*
13
*
12
*
11
*
Col
128Mbit
Device
10
9
22
20
21
23
*
8
*
7
*
6
*
5
*
4
*
3
*
2
*
Note
2
Mode Write
10
*
9
*
22
*
20
*
21
*
19
*
18
*
17
*
16
*
15
*
14
*
13
*
12
*
Note
2
Summary
10
9
22
20
21
19/23
18/8
17/7
16/6
15/5
14/4
13/3
12/2
11
Table 8-8: SDRAM row/column address map