Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors—Memory Controller
Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
Developer’s Manual
August 2006
590
Order Number: 306262-004US
11.2.2.2
DDRI SDRAM Bank Sizes and Configurations
The MCU supports a memory subsystem ranging from 32 Mbyte to 1 Gbyte for 32-bit
memory systems. An ECC or non-ECC system may be implemented using x8, or x16
devices.
illustrates the supported DDRI SDRAM configurations.
The 128/256/512-Mbit, 1-Gbit DDRI SDRAM devices comprise four internal leaves. The
MCU controls the leaf selects within 128/256/512 Mbit, 1 Gbit DDRI SDRAM by toggling
DDRI_BA[0] and DDRI_BA[1].
The two DDRI SDRAM chip enables DDRI_CS_N[1:0] support an DDRI SDRAM memory
subsystem consisting of two banks. The base address for the two contiguous banks are
programmed in the DDRI SDRAM Base Register (SDBR) and must be aligned to a
32 Mbyte boundary. The size of each DDRI SDRAM bank is programmed with the DDRI
SDRAM boundary registers (SBR0 and SBR1). Bank 0 is also configurable into multiple
regions.
Note:
Systems must implement memory devices of all the same bus width (x8, x16) due to
the single CAS address decode generated for a DDRI transaction. For example, systems
implementing ECC and using x16 devices for the 32 bit DDRI data bus must also use a
x16 device for the 8 bit ECC bus, even though 8 bits go unused.
Note:
For IXP45X/IXP46X network processors, the DDRI SDRAM 32-Bit Size Register (S32SR)
will not be used, since it will always be in 32-bit mode.
Table 203.
Supported DDRI SDRAM Configurations
DDRI
SDRAM
Technology
DDRI SDRAM
Arrangement
# Banks
Address Size
Leaf Select
Total
Memory
Size
1
1. Table indicates 32-bit wide memory subsystem sizes.
Page
Size
2
2. Table indicates 32-bit wide memory page sizes.
Row
Column DDRI_BA[1
]
DDRI_BA[0]
128 Mbit
3
3. Supported with DDRI SDRAM only
16 M x 8
1
12
10
ADDR[26]
ADDR[25]
64 M
4K
2
128 M
4K
8 M x 16
1
12
9
ADDR[25]
ADDR[24]
32 M
2K
2
64 M
2K
256 Mbit
32 M x 8
1
13
10
ADDR[27]
ADDR[26]
128 M
4K
2
256 M
4K
16 M x 16
1
13
9
ADDR[26]
ADDR[25]
64 M
2K
2
128 M
2K
512 Mbit
64 M x 8
1
13
11
ADDR[28]
ADDR[27]
256 M
8K
2
512 M
8K
32 M x 16
1
13
10
ADDR[27]
ADDR[26]
128 M
4K
2
256 M
4K
1 Gbit
4
4. Supported with DDRI SDRAM only
128 M x 8
1
14
11
ADDR[29]
ADDR[28]
512 M
8K
2
1 G
8K
64 M x 16
1
14
10
ADDR[28]
ADDR[27]
256 M
4K
2
512 M
4K
