Intel
®
81341 and 81342—DDR SDRAM Memory Controller
Intel
®
81341 and 81342 I/O Processors
Developer’s Manual
December 2007
600
Order Number: 315037-002US
illustrates the DDR SDRAM initialization sequence.
When the DDR SDRAM subsystem implements ECC (
Correction and Detection” on page 607
), then initialization software initializes the entire
memory array with the 81341 and 81342. It is important that every memory location has
a valid ECC byte. The Application DMA includes a memory block fill mode which can be
used to fill the memory array with a constant (
Section 5.7.8, “Memory Block Fill
), thereby initializing the associated ECC bytes in the process. A
small portion of memory must be initialized by the Intel XScale
®
microarchitecture
software to store the ADMA descriptor. When the memory array is not initialized, the
microarchitecture may attempt to read memory locations beyond the specified word(s).
In this case, the DMCU reports an ECC error even though software did not specifically
request the un-initialized data.
Figure 88. DDR SDRAM Initialization Sequence (controlled with software)
A7798-01
VDD
VDDQ
VTT
(System*)
CK
CK#
VREF
CKE
DM
A0-A9, A11
A10
BA0, BA1
DQS
DQ
Power-up:
VDD and CK stable
Command
200µs
t
CH
t
CL
t
CK
t
MRD
t
MRD
t
RFC
t
RFC
t
MRD
t
RP
t
IS
t
IH
t
IS
t
IH
NOP
PRE
EMRS
MRS
MRS
PRE
AR
AR
ACT
t
IS
t
IH
200 cycles of CK**
t
IS
t
IH
CODE
CODE
CODE
RA
t
IS
t
IH
CODE
All Banks
High-Z
High-Z
BA1=L
BA1=L
BA1=L
CODE
CODE
RA
t
IS
t
IH
BA0=
H
BA0=
L
BA0=
L
RA
t
IS
t
IH
All Banks
t
VTD
LVCMOS Low Level
Notes:
*
VTT is not applied directly to the device, however t
VTD
must be greater than or equal to zero to avoid device latchup.
**
t
MRD
is required before any command can be applied and 200 cycles of CK are required before a Read command
can be applied.
The two Autorefresh commands may be moved to follow the first MRS, but precede the second Precharge All
command.
= Don't Care
Extended Mode
Register Set
Load Mode
Register, Reset DLL
Load Mode
Register
(with A8=L)