SDRAM
AS4SD4M16
Austin Semiconductor, Inc.
Fixed-length or full-page WRITE bursts can be
PRECHARGE
truncated with the BURST TERMINATE command. When
truncating a WRITE burst, the input data applied coincident
with the BURST TERMINATE command will be ignored. The
last data written (provided that DQM is LOW at that time) will
be the input data applied one clock previous to the BURST
TERMINATE command. This is shown in Figure 19, where data
n is the last desired data element of a longer burst.
The PRECHARGE command is used to deactivate the
open row in a particular bank or the open row in all banks. The
bank(s) will be available for a subsequent row access some
specified time (tRP) after the PRECHARGE command is issued.
Input A10 determines whether one or all banks are to be
precharged, and in the case where only one bank is to be
precharged, inputs BA0, BA1 select the bank. When all banks
are to be precharged, inputs BA0, BA1 are treated as “Don’t
Care.” Once a bank has been precharged, it is in the idle state
and must be activated prior to any READ or WRITE commands
being issued to that bank.
T0
T1
T2
CLK
POWER-DOWN
Power-down occurs if CKE is registered LOW
coincident with a NOP or COMMAND INHIBIT when no
accesses are in progress. If power-down occurs when all banks
are idle, this mode is referred to as precharge power-down; if
power-down occurs when there is a row active in either bank,
this mode is referred to as active power-down. Entering power-
down deactivates the input and output buffers, excluding CKE,
for maximum power savings while in standby. The device may
not remain in the power-down state longer than the refresh
period (64ms/16ms) since no refresh operations are performed
in this mode.
BURST
TERMI-
NATE
NEXT
COMMAND
WRITE
COMMAND
BANK,
COL n
(ADDRESS)
ADDRESS
DIN
n
(DATA)
DQ
NOTE: DQMs is LOW.
Figure 19
TERMINATING A WRITE BURST
The power-down state is exited by registering a NOP
or COMMAND INHIBIT and CKE HIGH at the desired clock
edge (meeting tCKS).
CLK
HIGH
CKE
CS\
CLK
RAS\
CAS\
t
>t
CKS
CKS
CKE
WE\
A0-A9
COMMAND
NOP
ALL BANKS
NOP
ACTIVE
A10
BA
All banks idle
BANK SELECTED
BANK ADDRESS
t
t
t
RCD
RAS
RC
Input buffers gated off
Enter power-down mode.
Exit power-down mode.
DON’T CARE
Figure 20
PRECHARGE COMMAND
Figure 21
POWER-DOWN
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
AS4SD4M16
Rev. 1.5 10/01
21
AUSTIN [ AUSTIN SEMICONDUCTOR ]
