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MEMORY CONTROLLER
5.7.4 SDRAM COMMANDS
The SDRAM controller issues specific commands to the SDRAM devices by encoding the nSDCS, nSDRAS,
nSDCAS and nSDWE outputs. Table 5-23. Lists all of the SDRAM commands understood by SDRAM devices.
The controller supports a subset of these commands.
Command
Mode Register Set (MRS)
Refresh
Auto refresh
Self refresh
Row activate
Read
with auto
precharge
without auto
precharge
Write
with auto
precharge
without auto
precharge
Burst stop
Precharge Bank selection
All banks
Active power down
Precharge power down
No operation
NOTE: Shaded boxes indicate commands not supported by SDRAM controller. They are included for completeness.
X = Don't care
V = Valid value (H or L)
A10/AP = ADDR[10] /Auto Pre-charge
5-44
Table 5-23. SDRAM Commands
CKE
nSDCS
nSDRAS nSDCAS nSDWE
H
L
L
H
L
L
L
L
L
H
L
L
H
L
H
H
L
H
H
L
H
H
L
L
L
H
X
L
H
X
H
H
H
BA
L
L
OP code
L
H
L
H
H
H
V
L
H
V
L
L
V
H
L
H
L
V
X
X
X
X
X
H
H
S3C2500B
A10/AP Mnemonic
MRS
X
REF
SREF
X
ACT
H
RDA
L
RD
H
WRA
L
WR
X
BST
L
PRE
H
PALL
X
APWDN
PPWDN
NOP
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