AS4C4M16SA - Automotive
The BankPrecharge/PrechargeAll command that interrupts a write burst without the auto precharge function
should be issued m cycles after the clock edge in which the last data-in element is registered, where m 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
T7
CLK
DQM
tRP
WRITE
NOP
NOP
Precharge
Bank (s)
NOP
NOP
Activate
NOP
COMMAND
ADDRESS
DQ
Bank
Col n
ROW
tWR
DIN
n
DIN
N+1
Don’t Care
Note: The LDQM/UDQM can remain low in this example if the length of the write burst is 1 or 2.
Figure 13. Write to Precharge
7
Write and AutoPrecharge command
(RAS# = "H", CAS# = "L", WE# = "L", BAs = Bank, A10 = "H", A0-A7 = Column Address)
The Write and AutoPrecharge command performs the precharge operation automatically after the write
operation. Once this command is given, any subsequent command can not occur within a time delay of
{(burst length -1) + tWR + tRP(min.)}. At full-page burst, only the write operation is performed in this
command and the auto precharge function is ignored.
T0
T1
T2
T3
T4
T5
T6
T7
T8
T9
CLK
Bank A
Activate
Bank A
Activate
WRITE A
Auto Precharge
NOP
NOP
NOP
NOP
NOP
NOP
NOP
COMMAND
tDAL
DIN A0
DIN A1
DQ
tDAL=tWR+tRP
Begin AutoPrecharge
Bank can be reactivated at
completion of tDAL
Figure 14. Burst Write with Auto-Precharge
(Burst Length = 2)
8
Mode Register Set command (RAS# = "L", CAS# = "L", WE# = "L", A0-A11 = Register Data)
The mode register stores the data for controlling the various operating modes of SDRAM. The Mode
Register Set command programs the values of CAS latency, Addressing Mode and Burst Length in the
Mode register to make SDRAM useful for a variety of different applications. The default values of the
Mode Register after power-up are undefined; therefore this command must be issued at the power-up
sequence. The state of pins A0~A9 and A11 in the same cycle is the data written to the mode register.
Two clock cycles are required to complete the write in the mode register (refer to the following figure). The
contents of the mode register can be changed using the same command and the clock cycle
requirements during operation as long as all banks are in the idle state.
Confidential
11
Rev. 1.0-63nm Mar. /2014
ALSC [ ALLIANCE SEMICONDUCTOR CORPORATION ]
