NT5SV64M4AT Datasheet, PDF (27/65 Pages) List of Unclassifed Manufacturers – 256Mb Synchronous DRAM

NT5SV64M4AT(L)
NT5SV32M8AT(L)
NT5SV16M16AT(L)
256Mb Synchronous DRAM
Data Mask
The SDRAM has a Data Mask function that can be used in conjunction with data read and write cycles. When the Data Mask is
activated (DQM high) during a write cycle, the write operation is prohibited immediately (zero clock latency). If the Data Mask is
activated during a read cycle, the data outputs are disabled and become high impedance after a two-clock delay, independent
of CAS latency.
Data Mask Activated during a Read Cycle
(Burst Length = 4, CAS Latency = 2)
T0
T1
T2
T3
T4
T5
T6
T7
T8
CK
DQM
COMMAND ^NOP
READ A
NOP
NOP
NOP
NOP
NOP
NOP
NOP
DQs
: “H” or “L”
DOUT A₀
DOUT A ₁
A two-clock delay before
the DQs become Hi-Z
No Operation Command
The No Operation Command should be used in cases when the SDRAM is in an idle or a wait state. The purpose of the No
Operation Command is to prevent the SDRAM from registering any unwanted commands between operations. A No Operation
Command is registered when CS is low with RAS, CAS, and WE held high at the rising edge of the clock. A No Operation Com-
mand will not terminate a previous operation that is still executing, such as a burst read or write cycle.
Deselect Command
The Deselect Command performs the same function as a No Operation Command. Deselect Command occurs when CS is
brought high, the RAS, CAS, and WE signals become don’t cares.
REV 1.0
May, 2001
27
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