AS4LC4M16S0 datasheet(10/24 Pages) ALSC

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ALLIANCE SEMICONDUCTOR

7/5/00

AS4LC4M16S0

AS4LC16M4S0

Device operation

Command

Pin settings

Description

Power up

The following sequence must be performed prior to normal

operation.

Apply power, start clock, and assert CKE and DQM high. All other

signals are NOP.

After power-up, pause for a minimum of 200µs.

CKE/DQM = high; all others NOP.

Precharge both banks.

Perform Mode Register Set command to initialize mode register.

Perform a minimum of 8 auto refresh cycles to stabilize internal

circuitry.

(Steps 4 and 5 may be interchanged.)

Mode register set

CS = RAS = CAS = WE = low;

A0~A11 = opcode

The mode register stores the user selected opcode for the SDRAM

operating modes. The CAS latency, burst length, burst type, test mode

and other vendor specific functions are selected/programmed during

the Mode Register Set command cycle. The default setting of the

mode register is not defined after power-up. The power-up and mode

Refer to the Mode Register Set table and timing for details.

Device deselect and no

operation

CS = high

The SDRAM performs a “no operation” (NOP) when RAS, CAS, and

WE = high. Since the NOP performs no operation, it may be used as

a wait state in performing normal SDRAM functions. The SDRAM is

deselected when CS is high. CS high disables the command decoder

such that RAS, CAS, WE and address inputs are ignored. Device

deselection is also considered a NOP.

Bank activation

CS = RAS = low; CAS = WE =

high; A0~A10 = row address;

BA0~BA1 = bank select

The SDRAM is configured with four internal banks. Use the Bank

Activate command to select a row in one of the idle banks. Initiate

a read or write operation after tRCD(min) from the time of bank

activation.

Burst read

CS = CAS = A10 = low; RAS =

WE = high; BA0~BA1 = bank

select, A0~A8 = column

address; (A9 = don’t care for

×8; A8,A9 = don’t care for

×16)

Use the Burst Read command to access a consecutive burst of data

from an active row in an active bank. Burst read can be initiated on

any column address of an active row. The burst length, sequence and

latency are determined by the mode register setting. The first output

data appears after the CAS latency from the read command. The

output goes into a high impedance state at the end of the burst

(BL = 1,2,4,8) unless a new burst read is initiated to form a gapless

output data stream. Terminate the burst with a burst stop command,

precharge command to the same bank or another burst read/write.

Burst write

CS = CAS = WE = A10 = low;

RAS = high; A0~A9 = column

address; (A9 = don’t care for

×8; A8,A9 = don’t care for

×16)

Use the Burst Write command to write data into the SDRAM on

consecutive clock cycles to adjacent column addresses. The burst

length and addressing mode is determined by the mode register

opcode. Input the initial write address in the same clock cycle as the

Burst Write command. Terminate the burst with a burst stop

command, precharge command to the same bank or another burst

read/write.

UDQM/LDQM (

×16),

DQM (

×8) operation

Use DQM to mask input and output data on a cycle-by-cycle basis. It

disables the output buffers in a read operation and masks input data in

a write operation. The output data is invalid 2 clocks after DQM

assertion (2 clock latency). Input data is masked on the same clock as

DQM assertion (0 clock latency).

AS4LC4M16S0 Datasheet(PDF) 10 Page - Alliance Semiconductor Corporation

AS4LC4M16S0 Datasheet(HTML) 10 Page - Alliance Semiconductor Corporation

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