Marvell GT-64260A, Руководство по конструкции

Страница: 36 / 163

GT-64260A Design Guide
Doc. No. MV-S300165-00, Rev. A
CONFIDENTIAL
Copyright © 2002 Marvell
Page 36 Document Classification: Proprietary Information May 21, 2002, Preliminary
Table 8 describes different address pins during the RAS* and CAS* cycles. This indicates that when using a
"wider" (more data lines) device, less devices are needed, in total, to achieve the 64-bit data width. For example,
to use a 64 MB SDRAM device with a 8-bits wide configuration, connect eight devices in parallel to get 64-bits
data width
è 64 MB-memory space. Or, when using the same device in 16-bits wide configuration, connect four
devices in parallel in order to get 64-bits data width
è
32 MB-memory space. The example shows that the widest
SDRAM device provides the smallest memory space (for a given SDRAM density) because less devices are used.
Table 9 describes the SDRAM memory space for various SDRAM devices:
128 Mb
(4 virtual banks) Row A0 - A11 A0 - A11 A0 - A11 A0 - A11
Column A0 - A9, A11 A0 - A9 A0 - A8 A0 - A7
256 Mb
(4 virtual banks) Row A0 - A12 A0 - A12 A0 - A12 A0 - A12
Column A0 - A9, A11 A0 - A9 A0 - A8 A0 - A7
512 Mb
(4 virtual banks) Row A0 - A12 A0 - A12 A0 - A12 NA
Column A0 - A9, A11, A12 A0 - A9, A11 A0 - A9 NA
Table 9: SDRAM Memory Space
Device
Density Device
Width Memory Space per SCS* Total Memory Space
SCS*[3:0]
16 Mb X4 16 Mbit x 16 devices = 32 MB 32 MB x 4 = 128 MB
16 Mb X8 16 Mbit x 8 devices = 16 MB 16 MB x 4 = 64 MB
64 Mb X4 64 MB x 16 devices = 128 MB 128 MB x 4 = 512 MB
64 Mb X8 64 MB x 8 devices = 64 MB 64 MB x 4 = 256 MB
64 Mb X16 64 MB x 4 devices = 32 MB 32 MB x 4 = 128 MB
64 Mb X32 64 MB x 2 devices = 16 MB 16 MB x 4 = 64 MB
128 Mb X4 128 MB x 16 devices = 256 MB 256 MB x 4 = 1024 MB (1 GB)
128 Mb X8 128 MB x 8 devices = 128 MB 128 MB x 4 = 256 MB
128 Mb X16 128 MB x 4 devices = 64 MB 64 MB x 4 = 128 MB
128 Mb X32 128 MB x 2 devices = 32 MB 32 MB x 4 = 64 MB
256 Mb X4 256 MB x 16 devices = 512 MB 512 MB x 4 = 2048 MB (2 GB)
256 Mb X8 256 MB x 8 devices = 256 MB 256 MB x 4 = 1024 MB (1 GB)
256 Mb X16 256 MB x 4 devices = 128 MB 128 MB x 4 = 512 MB
256 Mb X32 256 MB x 2 devices = 64 MB 64 MB x 4 = 128 MB
512 Mb X4 512 MB x 16 devices = 1024 MB 1024 MB x 4 = 4096 MB (4 GB)
512 Mb X8 512 MB x 8 devices = 512 MB 512 MB x 4 = 2048 MB (2 GB)
Table 8: SDRAM Interface Pinout Description (Continued)
SDRAM Addressing x4 x8 x16 x32