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2

ALLIANCE SEMICONDUCTOR

7/5/00

AS4LC4M16S0

AS4LC16M4S0

Functional description

The AS4LC8M8S0 and AS4LC4M16S0 are high-performance 64-megabit CMOS Synchronous Dynamic Random Access

Memory (SDRAM) devices organized as 2,097,152 words × 8 bits × 4 banks, and 1,048,576 words × 16 bits × 4 banks,

respectively. Very high bandwidth is achieved using a pipelined architecture where all inputs and outputs are referenced to the

rising edge of a common clock. Programmable burst mode can be used to read up to a full page of data without selecting a

new column address.

The four internal banks can be alternately accessed (read or write) at the maximum clock frequency for seamless interleaving

operations. This provides a significant advantage over asynchronous EDO and fast page mode devices.

This SDRAM product also features a programmable mode register, allowing users to select read latency as well as burst length

and type (sequential or interleaved). Lower latency improves first data access in terms of CLK cycles, while higher latency

improves maximum frequency of operation. This feature enables flexible performance optimization for a variety of

applications.

DRAM commands and functions are decoded from control inputs. Basic commands are as follows:

The 64 Mb DRAM devices are available in 400-mil plastic TSOP II packages and have 54 pins in each configuration. Both

devices operate with a power supply of 3.3V ± 0.3V. Multiple power and ground pins are provided for low switching noise

and EMI. Inputs and outputs are LVTTL-compatible.

Logic block diagram

• Mode register set

• Deactivate bank

• Deactivate all banks

• Select row; activate bank

• Select column; write

• Select column; read

• Deselect; power down

• CBR refresh

• Auto precharge with read/write • Self-refresh

RAS

CAS

WE

CLK

CKE

Clock generator

Mode register

Row

address

buffer

Refresh

counter

Column

address

buffer

Burst

counter

Column decoder and

latch circuit

Data control circuit

DQ

A[11:0]

CS

Bank select

BA0, BA1

(4096×256×16)

(4096×256×16)

(4096×256×16)

(4096×256×16)

Sense amplifier