Discontinued (8/99 - last order; 12/99 - last ship)
IBM0364804 IBM0364164
IBM0364404 IBM03644B4
64Mb Synchronous DRAM - Die Revision B
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
CLK
DQM
NOP
READ A
NOP
NOP
NOP
NOP
NOP
NOP
NOP
COMMAND
DOUT A0
DQs
DOUT A1
A two clock delay before
the DQs become Hi-Z
: “H” or “L”
No Operation Command
The No Operation Command should be used in cases when the SDRAM is in a idle or a wait state. The pur-
pose 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 Command 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.
©IBM Corporation. All rights reserved.
Use is further subject to the provisions at the end of this document.
19L3264.E35855A
1/28/99
Page 30 of 72
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