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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
598
Order Number: 306262-004US
11.2.2.7
DDRI SDRAM Commands
The MCU issues specific commands to the DDRI SDRAM devices by encoding them on
the DDRI_CS_N[1:0], DDRI_RAS_N, DDRI_CAS_N, and DDRI_WE_N inputs.
lists all of the DDRI SDRAM commands understood by DDRI SDRAM devices. The MCU
supports a subset of these commands.
DDRI SDRAM commands are synchronous to the clock so the MCU sets up the above
conditions prior to the DDRI_CK[2:0] rising edge.
11.2.2.8
DDRI SDRAM Initialization
Since DDRI SDRAM devices contain a controller within the device, the MCU must
initialize them specifically. Upon the deassertion of RESET_IN_N, software initializes the
DDRI SDRAM devices with the sequence described below and illustrated in
1. The MCU applies the clock DDRI_CK[2:0] at power up along with system power
(clock frequency unknown).
2. The MCU must stabilize DDRI_CK[2:0] within 100 µs after power stabilizes.
3. The MCU holds the following control inputs inactive:
DDRI_RAS_N, DDRI_CAS_N, DDRI_WE_N, DDRI_CS_N[1:0]
Table 211.
DDRI SDRAM Commands
Command
1,2
1. This table copied from New DRAM Technologies by Steven Przybylski.
2. Shaded boxes indicate commands not supported by IXP45X/IXP46X network processors. They are included for completeness.
Conditions
Comments
DDRI_
CS_N[1:0
]
DDRI_
RAS_N
DDRI_
CAS_N
DDRI_
WE_N
Other
NOP
0
1
1
1
No Operation
Mode Register Set
0
0
0
0
DDRI_BA[0]
= Sel
3
DDRI_BA[1] = 0
3. During a Mode Register Set command, DDRI_BA[1:0] = 00
2
selects the Mode Register, DDRI_BA[1:0] = 01
2
selects the
Extended Mode Register, all others are served.
Load the (Extended) Mode
Register from DDRI_MA[13:0]
Row Activate
0
0
1
1
DDRI_BA[1:0] = Leaf Activate a row specified on
DDRI_MA[13:0]
Read
0
1
0
1
DDRI_BA[1:0] = Leaf
DDRI_MA[10] = 0
Column burst read
Column address on
DDRI_MA[13:0]
Read w/ Auto-
Precharge
0
1
0
1
DDRI_BA[1:0] = Leaf
DDRI_MA[10] = 1
Column burst read with row
precharge at the end of the
transfer
Write
0
1
0
0
DDRI_BA[1:0] = Leaf
DDRI_MA[10] = 0
Column burst write
Column address on
DDRI_MA[13:0]
Write w/ Auto-
Precharge
0
1
0
0
DDRI_BA[1:0] = Leaf
DDRI_MA[10] = 1
Column burst write with row
precharge at the end of the
transfer
Precharge
0
0
1
0
DDRI_BA[1:0] = Leaf
DDRI_MA[10] = 0
Precharge a single leaf
Precharge All
0
0
1
0
DDRI_MA[10] = 1
Precharge all leaves
Auto-Refresh
0
0
0
1
Refresh both banks from on-chip
refresh counter
Self-Refresh
0
0
0
1
CKE = 0
Refresh autonomously while CKE
= 0
Power Down
X
X
X
X
CKE = 0
Power down if both banks
precharged when CKE = 0
Stop
0
1
1
0
Interrupt a read or write burst.