EtronTech
EM638325
2Mega x 32 SDRAM
T0
T1
T2
T3
T4
T5
T6
T7
T8
CLK
NOP
NOP
NOP
COMMAND
NOP
WRITE A
WRITE B
NOP
NOP
NOP
1 Clk Interval
DIN DIN B
A
DIN B
DIN B
DIN B
3
DQ's
0
0
1
2
Write Interrupted by a Write (Burst Length = 4, CAS# Latency = 1, 2, 3)
The Read command that interrupts a write burst without auto precharge function should be
issued one cycle after the clock edge in which the last data-in element is registered. In order to avoid
data contention, input data must be removed from the DQs at least one clock cycle before the first
read data appears on the outputs (refer to the following figure). Once the Read command is
registered, the data inputs will be ignored and writes will not be executed.
T0
T 1
T2
T3
T4
T5
T6
T7
T8
CLK
NOP
NOP
NOP
COMMAND
CAS# latency=2
NOP
WRITE A
READ B
don't care
don't care
NOP
NOP
NOP
DOUT B
DOUT B
DIN A
0
DOUT B
DOUT B
2
3
0
1
t
, DQ's
CK2
CAS# latency=3
, DQ's
DOUT B
DOUT B
DOUT B
DOUT B
3
DIN A
0
don't care
t
0
1
2
CK3
Input data must be removed from the DQ's at least one clock
cycle before the Read data appears on the outputs to avoid
data contention.
Input data for the write is masked.
Write Interrupted by a Read (Burst Length = 4, CAS# Latency = 2, 3)
The BankPrecharge/PrechargeAll command that interrupts a write burst without the auto
m
precharge function should be issued cycles after the clock edge in which the last data-in element
m
is registered, where
equals tWR/tCK rounded up to the next whole number. In addition, the DQM
signals must be used to mask input data, starting with the clock edge following the last data-in
element and ending with the clock edge on which the BankPrecharge/PrechargeAll command is
entered (refer to the following figure).
T0
T1
T2
T3
T4
T5
T6
CLK
DQM
t
RP
COMMAND
WRITE
Precharge
BANK (S)
NOP
NOP
Activate
ROW
NOP
NOP
BANK
COL n
ADDRESS
DQ
t
WR
DIN
n
DIN
n + 1
: don't care
Note:
The DQMs can remain low in this example if the length of the write burst is 1 or 2.
Write to Precharge
Preliminary
10
Rev 1.4
Oct. 2005
ETRON [ ETRON TECHNOLOGY, INC. ]
