MT48LC128M4A2A2TG-75 View Datasheet(PDF) - Micron Technology

Part Name

Description

Manufacturer

MT48LC128M4A2A2TG-75

SYNCHRONOUS DRAM

Micron Technology 

Operation

BANK/ROW ACTIVATION

Before any READ or WRITE commands can be issued

to a bank within the SDRAM, a row in that bank must be

“opened.” This is accomplished via the ACTIVE com-

mand, which selects both the bank and the row to be

activated (see Figure 3).

After opening a row (issuing an ACTIVE command), a

READ or WRITE command may be issued to that row,

subject to the tRCD specification. tRCD (MIN) should be

divided by the clock period and rounded up to the next

whole number to determine the earliest clock edge after

the ACTIVE command on which a READ or WRITE com-

mand can be entered. For example, a tRCD specification

of 20ns with a 125 MHz clock (8ns period) results in 2.5

clocks, rounded to 3. This is reflected in Figure 4, which

covers any case where 2 < tRCD (MIN)/tCK - 3. (The same

procedure is used to convert other specification limits

from time units to clock cycles.)

A subsequent ACTIVE command to a different row in

the same bank can only be issued after the previous

active row has been “closed” (precharged). The mini-

mum time interval between successive ACTIVE com-

mands to the same bank is defined by tRC.

A subsequent ACTIVE command to another bank can

be issued while the first bank is being accessed, which

results in a reduction of total row-access overhead. The

minimum time interval between successive ACTIVE com-

mands to different banks is defined by tRRD.

ADVANCE

512Mb: x4, x8, x16

SDRAM

CLK

CKE HIGH

CS#

RAS#

CAS#

WE#

A0-A12

ROW

ADDRESS

BA0, BA1

BANK

ADDRESS

Figure 3

Activating a Specific Row In a

Specific Bank

T0

T1

T2

T3

T4

CLK

COMMAND

ACTIVE

NOP

NOP

READ or

WRITE

tRCD

DON’T CARE

Figure 4

Example: Meeting tRCD (MIN) When 2 < tRCD (MIN)/tCK < 3

512Mb: x4, x8, x16 SDRAM

512MSDRAM_D.p65 – Rev. D; Pub 1/02

14

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

©2000, Micron Technology, Inc.

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