
Preliminary 
 A48P3616   
      8M X 16 Bit DDR DRAM
Preliminary (September 2005, Version 0.0) 
19
AMIC Technology, Corp.
Device Operations 
Deselect 
The Deselect function prevents new commands from being 
executed by the DDR SDRAM. The DDR SDRAM is 
effectively deselected. Operations already in progress are not 
affected. 
No Operation (NOP) 
The No Operation (NOP) command is used to perform a NOP 
to a DDR SDRAM. This prevents unwanted commands from 
being registered during idle or wait states. Operations already 
in progress are not affected. 
Mode Register Set 
The mode registers are loaded via inputs A0-A11, BA0 and 
BA1 while issuing the Mode Register Set Command. See 
mode register descriptions in the Register Definition section. 
The Mode Register Set command can only be issued when 
all banks are idle and no bursts are in progress. A subsequent 
executable command cannot be issued until t
MRD
is met. 
Active 
The Active command is used to open (or activate) a row in a 
particular bank for a subsequent access. The value on the 
BA0, BA1 inputs selects the bank, and the address provided 
on inputs A0-A11 selects the row. This row remains active (or 
open) for accesses until a Precharge (or Read or Write with 
Auto Precharge) is issued to that bank. A Precharge (or Read 
or Write with Auto Precharge) command must be issued and 
completed before opening a different row in the same bank. 
Read 
The Read command is used to initiate a burst read access to 
an active (open) row. The value on the BA0, BA1 inputs 
selects the bank, and the address provided on inputs A0-A8 
selects the starting column location. The value on input A10 
determines whether or not Auto Precharge is used. If Auto 
Precharge is selected, the row being accessed is precharged 
at the end of the Read burst; if Auto Precharge is not selected, 
the row remains open for subsequent accesses. 
Write 
The Write command is used to initiate a burst write access to 
an active (open) row. The value on the BA0, BA1 inputs 
selects the bank, and the address provided on inputs A0-A8 
selects the starting column location. The value on input A10 
determines whether or not Auto Precharge is used. If Auto 
Precharge is selected, the row being accessed is precharged 
at the end of the Write burst; if Auto Precharge is not selected, 
the row remains open for subsequent accesses. Input data 
appearing on the DQs is written to the memory array subject 
to the DM input logic level appearing coincident with the data. 
If a given DM signal is registered low, the corresponding data 
is written to memory; if the DM signal is registered high, the 
corresponding data inputs are ignored, and a Write is not 
executed to that byte/column location. 
Precharge 
The Precharge command is used to deactivate (close) the 
open row in a particular bank or the open row(s) in all banks. 
The bank(s) will be available for a subsequent row access a 
specified time (t
RP
) after the Precharge command is issued. 
Input A10 determines whether one or all banks are to be 
precharged, and in the case where only one bank is to be 
precharged, inputs BA0, BA1 select the bank. Otherwise BA0, 
BA1 are treated as “Don’t Care.” Once a bank has been 
precharged, it is in the idle state and must be activated prior 
to any Read or Write commands being issued to that bank. A 
precharge command is treated as a NOP if there is no open 
row in that bank, or if the previously open row is already in the 
process of precharging.
Auto Precharge 
Auto Precharge is a feature which performs the same 
individual-bank precharge function described above, but 
without requiring an explicit command. This is accomplished 
by using A10 to enable Auto Precharge in conjunction with a 
specific Read or Write command. A precharge of the 
bank/row that is addressed with the Read or Write command 
is automatically performed upon completion of the Read or 
Write burst. Auto Precharge is non-persistent in that it is 
either enabled or disabled for each individual 
Read or Write command. Auto Precharge ensures that the 
precharge is initiated at the earliest valid stage within a burst. 
This is determined as if an explicit Precharge command was 
issued at the earliest possible time without violating t
RAS(min)
. 
The user must not issue another command to the same bank 
until the precharge (t
RP
) is completed. 
The NTC DDR SDRAM devices supports the optional t
RAS
lockout feature. This feature allows a Read command with 
Auto Precharge to be issued to a bank that has been 
activated (opened) but has not yet satisfied the t
RAS(min)
specification. The t
RAS
lockout feature essentially delays the 
onset of the auto precharge operation until two conditions 
occur. One, the entire burst length of data has been 
successfully prefetched from the memory array; and two, 
t
RAS(min)
 has been satisfied. 
As a means to specify whether a DDR SDRAM device 
supports the t
RAS
lockout feature, a new parameter has been 
defined, t
RAP
(RAS Command to Read Command with Auto 
Precharge or better stated Bank Activate to Read Command 
with Auto Precharge). For devices that support the t
RAS
lockout feature, t
RAP
= t
RCD(min)
. This allows any Read 
Command (with or without Auto Precharge) to be issued to an 
open bank once t
RCD(min)
 is satisfied.
Burst Terminate 
The Burst Terminate command is used to truncate read 
bursts (with Auto Precharge disabled). The most re-cently 
registered Read command prior to the Burst Terminate 
command is truncated, as shown in the Operation section of 
this data sheet. Write burst cycles are not to be terminated 
with the Burst Terminate command.