EtronTech
EM636165-XXI
1M x 16 SDRAM
Commands
1
BankPrecharge command
(RAS# = "L", CAS# = "H", WE# = "L", A11 = “V”, A10 = "L", A0-A9 = Don't care)
The BankPrecharge command precharges the bank disignated by A11 signal. The precharged
bank is switched from the active state to the idle state. This command can be asserted anytime after
tRAS(min.) is satisfied from the BankActivate command in the desired bank. The maximum time any
bank can be active is specified by tRAS(max.). Therefore, the precharge function must be performed
in any active bank within tRAS(max.). At the end of precharge, the precharged bank is still in the idle
state and is ready to be activated again.
2
3
PrechargeAll command
(RAS# = "L", CAS# = "H", WE# = "L", A11 = Don't care, A10 = "H", A0-A9 = Don't care)
The PrechargeAll command precharges both banks simultaneously and can be issued even if
both banks are not in the active state. Both banks are then switched to the idle state.
Read command
(RAS# = "H", CAS# = "L", WE# = "H", A11= “V”, A9 = "L", A0-A7 = Column Address)
The Read command is used to read a burst of data on consecutive clock cycles from an active
row in an active bank. The bank must be active for at least tRCD(min.) before the Read command is
issued. During read bursts, the valid data-out element from the starting column address will be
available following the CAS# latency after the issue of the Read command. Each subsequent data-
out element will be valid by the next positive clock edge (refer to the following figure). The DQs go
into high-impedance at the end of the burst unless other command is initiated. The burst length,
burst sequence, and CAS# latency are determined by the mode register, which is already
programmed. A full-page burst will continue until terminated (at the end of the page it will wrap to
column 0 and continue).
T0
T1
T2
T3
T4
T5
T6
T7
T8
CLK
COMMAND
READ A
NOP
NOP
NOP
NOP
NOP
NOP
NOP
NOP
CAS# latency=1
DOUT A
DOUT A
DOUT A
DOUT A
3
0
1
2
t
, DQ's
CK1
CAS# latency=2
, DQ's
DOUT A
DOUT A
DOUT A
DOUT A
3
0
1
2
t
CK2
CAS# latency=3
, DQ's
DOUT A
DOUT A
1
DOUT A
DOUT A
3
0
2
t
CK3
Burst Read Operation
(Burst Length = 4, CAS# Latency = 1, 2, 3)
Preliminary
6
Rev. 1.1 Apr. 2005
ETRON [ ETRON TECHNOLOGY, INC. ]
