MT48LC16M4A2 查看數據表（PDF） - Micron Technology

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MT48LC16M4A2

64Mb: x4, x8, x16 SDRAM

Micron Technology 

64Mb: x4, x8, x16

SDRAM

COMMAND INHIBIT

The COMMAND INHIBIT function prevents new

commands from being executed by the SDRAM, re-

gardless of whether the CLK signal is enabled. The

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 an SDRAM which is selected (CS# is

LOW). This prevents unwanted commands from being

registered during idle or wait states. Operations already

in progress are not affected.

LOAD MODE REGISTER

The mode register is loaded via inputs A0-A11. See

mode register heading in the Register Definition section.

The LOAD MODE REGISTER command can only be is-

sued when all banks are idle, and a subsequent execut-

able command cannot be issued until tMRD 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 command is issued to that bank.

A PRECHARGE command must be issued before open-

ing a different row in the same bank.

READ

The READ command is used to initiate a burst read

access to an active row. The value on the BA0, BA1

inputs selects the bank, and the address provided on

inputs A0-A9 (x4), A0-A8 (x8), or A0-A7 (x16) selects the

starting column location. The value on input A10 de-

termines whether or not auto precharge is used. If auto

precharge is selected, the row being accessed will be

precharged at the end of the READ burst; if auto

precharge is not selected, the row will remain open for

subsequent accesses. Read data appears on the DQs

subject to the logic level on the DQM inputs two clocks

earlier. If a given DQM signal was registered HIGH, the

corresponding DQs will be High-Z two clocks later; if

the DQM signal was registered LOW, the DQs will pro-

vide valid data.

precharge is selected, the row being accessed will be

precharged at the end of the WRITE burst; if auto

precharge is not selected, the row will remain open for

subsequent accesses. Input data appearing on the DQs

is written to the memory array subject to the DQM in-

put logic level appearing coincident with the data. If a

given DQM signal is registered LOW, the correspond-

ing data will be written to memory; if the DQM signal is

registered HIGH, the corresponding data inputs will

be ignored, and a WRITE will not be executed to that

byte/column location.

PRECHARGE

The PRECHARGE command is used to deactivate

the open row in a particular bank or the open row in all

banks. The bank(s) will be available for a subsequent

row access a specified time (tRP) 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.

AUTO PRECHARGE

Auto precharge is a feature which performs the

same individual-bank PRECHARGE function de-

scribed above, 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 ad-

dressed with the READ or WRITE command is auto-

matically performed upon completion of the READ or

WRITE burst, except in the full-page burst mode, where

auto precharge does not apply. 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 initi-

ated at the earliest valid stage within a burst. The user

must not issue another command to the same bank

until the precharge time (tRP) is completed. This is

determined as if an explicit PRECHARGE command

was issued at the earliest possible time, as described

for each burst type in the Operation section of this data

sheet.

WRITE

The WRITE command is used to initiate a burst write

access to an active row. The value on the BA0, BA1

inputs selects the bank, and the address provided on

inputs A0-A9 (x4), A0-A8 (x8), or A0-A7 (x16) selects the

starting column location. The value on input A10 de-

termines whether or not auto precharge is used. If auto

BURST TERMINATE

The BURST TERMINATE command is used to trun-

cate either fixed-length or full-page bursts. The most

recently registered READ or WRITE command prior to

the BURST TERMINATE command will be truncated,

as shown in the Operation section of this data sheet.

64Mb: x4, x8, x16 SDRAM

64MSDRAM_F.p65 – Rev. F; Pub. 1/03

12

Micron Technology, Inc., reserves the right to change products or specifications without notice.

©2003, Micron Technology, Inc.

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