Intel
®
81341 and 81342—DDR SDRAM Memory Controller
Intel
®
81341 and 81342 I/O Processors
Developer’s Manual
December 2007
582
Order Number: 315037-002US
The Secondary Memory Window is setup using the
Table 379, “Secondary SDRAM Base
and bits [21:16] of the
. Note that the secondary memory window simply
provides a second decoding window to access part of the same SDRAM memory space.
For example, programming the DMCU to provide a secondary memory window does not
affect the way the DMCU does the internal bus address mapping to generate the Bank
Address/Row Address/Column Address as described in
and
Section 7.3.3.3, “DDR SDRAM Bank Sizes and
. If a 32-bit memory region is defined and a secondary
memory window is also defined and it overlaps the 32-bit memory region, then
transactions made via the secondary memory window that hit the 32-bit region will
occur as 32-bit transactions.
Warning:
When supporting both the Primary and Secondary Memory Windows, the Programmer
must always initialize and setup the DMCU with respect to the Primary Memory Window
first, as if the Secondary Memory Window does not exist. Only after setting up the
Primary Memory Window, the Programmer can setup and enable the Secondary
Memory Window as explained below. This is because the Secondary Memory Window is
used in conjunction with the Primary Memory Window.
Figure 82, “Secondary DDR SDRAM Window Memory Map” on page 582
shows how the
Secondary Memory Window is mapped relative to the entire SDRAM Memory space.
Note how the SDRAM Memory space is shown to be mapped in an upper 4-GByte of the
address space, and the secondary memory window is shown to be mapped in the
lowest 4-GByte of the address space.
illustrates an example where the
SDRAM Memory space is less than 4 GBytes. In this scenario, where the SDRAM space
is less than 4 GBytes, it is critical that the secondary memory window is defined so that
its address range in the lowest 4-GByte of the address space overlaps an address range
within the defined primary memory window.
Figure 82. Secondary DDR SDRAM Window Memory Map
Primary Window
(Bank 0)
32-bit
Region
SDBR[31:27] |
SDUBR[3:0]
Primary Window
(Bank 1)
SBSR[31:27]
SBSR[21:16]
Secondary Window
64-Bit
Region 0
64-Bit
Region 1
Any 4-Gbyte Address
Space
Lower 4-Gbyte Address
Space
Valid
Address
Range
for the
Secondary
Window
Note: Address Space shown are not to scale.
0
0
4GB
4GB
SSDBR
Entire
SDRAM
Space