Intel
®
81341 and 81342—DDR SDRAM Memory Controller
Intel
®
81341 and 81342 I/O Processors
Developer’s Manual
December 2007
594
Order Number: 315037-002US
7.3.3.7
DDR SDRAM Initialization
Since DDR SDRAM devices contain a controller within the device, the DMCU must
initialize them specifically. Upon the deassertion of internal bus reset, software
initializes the DDR SDRAM devices with the sequence illustrated with
.
However, before executing the DDR SDRAM initialization sequence provided below,
software must read the SPD (Serial Presence-Detect) data and then program the DMCU
parameters as explained in
Section 7.3.3.8, “DDR SDRAM Mode Programming” on
. The DMCU does
not
interact properly with the DDR SDRAM until these
parameters have been programmed.
1. The DMCU applies the clock (
M_CK[2:0]
) at power up along with system power
(clock frequency unknown).
2. The DMCU must stabilize
M_CK[2:0]
within 100 µs after power stabilizes.
3. The DMCU holds all the control inputs inactive (
RAS#
,
CAS#
,
WE#
,
SCE[1:0]# =
1
), places all data outputs and strobes in the High-Z state (
DQS[8:0]
,
DQS[8:0]#
,
DQ[71:0]
), and deasserts
CKE[1:0]
for a minimum of 200 us after
supply voltage reaches the desired level. Asserting
P_RST#
achieves this state.
4. Software disables the refresh counter by setting the RFR to zero.
5. Software issues one
NOP
cycle after the 200 us device deselect. A
NOP
is
accomplished by setting the SDIR to 0000_0070H. The DMCU asserts
CKE[1:0]
with the NOP.
6. Software issues a
precharge-all
command to the DDR SDRAM interface by setting
the SDIR to 0002_0020H.
7. Software issues an
extended-mode-register-set
2 (EMRS(2))
command by writing
0100_0000H to the SDIR.
8. Software issues an
extended-mode-register-set
3 (EMRS(3))
command by writing
0180_0000H to the SDIR.
9. Software issues an
extended-mode-register-set 1 (EMRS(1) )
command to enable DLL
by writing 0080_0000H
to SDIR. DMCU supports the following DDR and DDR2
SDRAM mode parameters:
a. DLL = Enable/Disable
b. Off-Chip Driver (OCD) Impedance Adjustment — applies to DDR2 SDRAM only.
c. Additive Latency (AL) is always zero for 81341 and 81342.
Figure 86. Supported DDR2 SDRAM Extended Mode Register Settings
0
0
A0
A12
The DDR SDRAM Extended
Mode Register resides in
the DDR SDRAM devices.
BA[1:0] must be 01
2
to select the Extended Mode Register.
A3
A6
0
Additive Latency
DLL Enable:
0 = Enable
1 = Disable
0
0
0
OCD Operation
RTT
Output Drive Strength
A10 A9
A7
B6260-01