AS4SD4M16(2001) Просмотр технического описания (PDF) - Austin Semiconductor

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AS4SD4M16
(Rev.:2001)

4 Meg x 16 SDRAM Synchronous DRAM Memory

Austin Semiconductor 

Austin Semiconductor, Inc.

SDRAM

AS4SD4M16

GENERAL DESCRIPTION

The 64Mb SDRAM is a high-speed CMOS, dynamic ran-

dom-access memory containing 67,108,864 bits. It is internally

configured as a quad-bank DRAM with a synchronous inter-

face (all signals are registered on the positive edge of the clock

signal, CLK). Each of the x16’s 6,777,216-bit banks is organized

as 4,096 rows by 256 columns by 16 bits.

Read and write accesses to the SDRAM are burst oriented;

accesses start at a selected location and continue for a pro-

grammed number of locations in a programmed sequence. Ac-

cesses begin with the registration of an ACTIVE command,

which is then followed by a READ or WRITE command. The

address bits registered coincident with the ACTIVE command

are used to select the bank and row to be accessed (BA0, BA1

select the bank; A0-A11 select the row). The address bits

registered coincident with the READ or WRITE command are

used to select the starting column location for the burst access.

The SDRAM provides for programmable READ or WRITE

burst lengths of 1, 2, 4 or 8 locations, or the full page, with a

burst terminate option. An AUTO PRECHARGE function may

be enabled to provide a self-timed row precharge that is initi-

ated at the end of the burst sequence.

The 64Mb SDRAM uses an internal pipelined architecture

to achieve high-speed operation. This architecture is compat-

ible with the 2n rule of prefetch architectures, but it also allows

the column address to be changed on every clock cycle to

achieve a high-speed, fully random access. Precharging one

bank while accessing one of the other three banks will hide the

precharge cycles and provide seamless, high-speed, random-

access operation.

The 64Mb SDRAM is designed to operate in 3.3V, low-

power memory systems. An auto refresh mode is provided,

along with a power-saving, power-down mode. All inputs and

outputs are LVTTL-compatible.

SDRAMs offer substantial advances in DRAM operating

performance, including the ability to synchronously burst data

at a high data rate with automatic column-address generation,

the ability to interleave between internal banks in order to hide

precharge time and the capability to randomly change column

addresses on each clock cycle during a burst access.

AS4SD4M16

Rev. 1.5 10/01

Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.

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