SDRAM Interface Functional Overview
SDRAM Address Control
Copyright © 2002 Marvell
CONFIDENTIAL
Doc. No. MV-S300165-00, Rev. A
May 21, 2002, Preliminary
Document Classification: Proprietary Information
Page 39
shows the ECC bank selection for each ECC bank per SCS* with various SDRAM configurations. The
guidelines for the ECC bank device selection are as follows:
•
ECC bank capacity must be at least 1:8 of SDRAM capacity.
•
ECC bank device type must be compatible to the SDRAM type. This means in the same group defined by the
SDRAM Bankx Parameters register’s
SDType
bits [15:14], at offsets 0x44c, 0x450, 0x454, 0x458.
4.3
SDRAM Address Control
The Address Control Register, at offset 0x47C, is a four-bit register that determines how address bits driven by the
CPU, PCI, or DMA to the SDRAM controller are translated to row and column address bits on DAdr[12:0] and
BankSel[1:0]. This flexibility allows the setting of the specific address decode setting which gives the software a
better chance of virtual banks interleaving and enhances overall system performance.
Note
The row and column address translation is different for 16 Mb, 64/128Mb, or 256/512 MB SDRAMs. For
more information, see the GT-64260A datasheet’s "SDRAM Density" section.
Table 10:
ECC Bank Selection
Device Density
Device Width
ECC Devices per SCS
16 Mb
X4
2 x 16 Mb (4-bit wide)
16 Mb
X8
1 x 16 Mb (8-bit wide)
64 Mb
X4
1 x 128 Mb (8-bit wide)
64 Mb
X8
1 x 64 Mb (8-bit wide)
64 Mb
X16
1 x 64 Mb (8-bit wide) – 50% used
64 Mb
X32
1 x 64 Mb (8-bit wide) – 25% used
128 Mb
X4
2 x 128 Mb (4-bit wide)
128 Mb
X8
1 x 128 Mb (8-bit wide)
128 Mb
X16
1 x 64 Mb (8-bit wide)
128 Mb
X32
1 x 64 Mb (8-bit wide) – 50% used
256 Mb
X4
1 x 512 Mb (8-bit wide)
256 Mb
X8
1 x 256 Mb (8-bit wide)
256 Mb
X16
1 x 256 Mb (8-bit wide) – 50% used
256 Mb
X32
1 x 256 Mb (8-bit wide) – 25% used
512 Mb
X4
2 x 512 Mb (4-bit wide)
512 Mb
X8
1 x 512 Mb (8-bit wide)
512 Mb
X16
1 x 256 Mb (8-bit wide)