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A43L0632G-7F

512K X 32 Bit X 2 Banks Synchronous DRAM

AMIC Technology 

A43L0632

Device Operations

Clock (CLK)

The clock input is used as the reference for all SDRAM

operations. All operations are synchronized to the positive

going edge of the clock. The clock transitions must be

monotonic between VIL and VIH. During operation with CKE

high all inputs are assumed to be in valid state (low or high)

for the duration of set up and hold time around positive edge

of the clock for proper functionality and ICC specifications.

Clock Enable (CKE)

The clock enable (CKE) gates the clock onto SDRAM. If

CKE goes low synchronously with clock (set-up and hold

time same as other inputs), the internal clock is suspended

from the next clock cycle and the state of output and burst

address is frozen as long as the CKE remains low. All other

inputs are ignored from the next clock cycle after CKE goes

low. When all banks are in the idle state and CKE goes low

synchronously with clock, the SDRAM enters the power

down mode from the next clock cycle. The SDRAM remains

in the power down mode ignoring the other inputs as long as

CKE remains low. The power down exit is synchronous as

the internal clock is suspended. When CKE goes high at

least “tSS + 1 CLOCK” before the high going edge of the

clock, then the SDRAM becomes active from the same clock

edge accepting all the input commands.

Bank Select (BA)

This SDRAM is organized as 2 independent banks of

524,288 words X 32 bits memory arrays. The BA inputs is

latched at the time of assertion of RAS and CAS to select

the bank to be used for the operation. The bank select BA is

latched at bank activate, read, write mode register set and

precharge operations.

Address Input (A0 ~ A10/AP)

The 19 address bits required to decode the 524,288 word

locations are multiplexed into 11 address input pins

(A0~A10/AP). The 11 bit row address is latched along with

RAS , BA during bank activate command. The 8 bit column

address is latched along with CAS , WE , BA during read

or write command.

NOP and Device Deselect

When RAS , CAS and WE are high, the SDRAM

performs no operation (NOP). NOP does not initiate any new

operation, but is needed to complete operations which

require more than single clock like bank activate, burst read,

auto refresh, etc. The device deselect is also a NOP and is

entered by asserting CS high. CS high disables the

command decoder so that RAS , CAS and WE , and all

the address inputs are ignored.

Power-Up

The following sequence is recommended for POWER UP

1. Power must be applied to either CKE and DQM inputs to

pull them high and other pins are NOP condition at the

inputs before or along with VDD (and VDDQ) supply.

The clock signal must also be asserted at the same time.

2. After VDD reaches the desired voltage, a minimum pause

of 200 microseconds is required with inputs in NOP

condition.

3. All banks must be precharged now.

4. Perform a minimum of 2 Auto refresh cycles to stabilize

the internal circuitry.

5. Perform a MODE REGISTER SET cycle to program the

CAS latency, burst length and burst type as the default

value of mode register is undefined.

At the end of one clock cycle from the mode register set

cycle, the device is ready for operation.

When the above sequence is used for Power-up, all the

out-puts will be in high impedance state. The high

impedance of outputs is not guaranteed in any other

power-up sequence.

cf.) Sequence of 4 & 5 may be changed.

Mode Register Set (MRS)

The mode register stores the data for controlling the various

operation modes of SDRAM. It programs the CAS latency,

addressing mode, burst length, test mode and various

vendor specific options to make SDRAM useful for variety of

different applications. The default value of the mode register

is not defined, therefore the mode register must be written

after power up to operate the SDRAM. The mode register is

written by asserting low on CS , RAS , CAS , WE (The

SDRAM should be in active mode with CKE already high

prior to writing the mode register). The state of address pins

A0~A10/AP, BA in the same cycle as

CS , RAS , CAS , WE going low is the data written in the

mode register. One clock cycle is required to complete the

write in the mode register. The mode register contents can

be changed using the same command and clock cycle

requirements during operation as long as all banks are in the

idle state. The mode register is divided into various fields

depending on functionality. The burst length field uses

A0~A2, burst type uses A3, addressing mode uses A4~A6,

A7~A8, A10/AP, BA are used for vendor specific options or

test mode. And the write burst length is programmed using

A7~A9, A10/AP, BA must be set to low for normal SDRAM

operation.

Refer to table for specific codes for various burst length,

addressing modes and CAS latencies. BA have to be set to

“0” to enter the Mode Register.

Bank Activate

The bank activate command is used to select a random row

in an idle bank. By asserting low on RAS and CS with

desired row and bank addresses, a row access is initiated.

The read or write operation can occur after a time delay of

tRCD(min) from the time of bank activation. tRCD(min) is an

internal timing parameter of SDRAM, therefore it is

dependent on operating clock frequency. The minimum

number of clock cycles required between bank activate and

read or write command should be calculated by dividing

tRCD(min) with cycle time of the clock and then rounding off

the result to the next higher integer. The SDRAM has 2

internal banks on the same chip and shares part of the

internal circuitry to reduce chip area, therefore it restricts the

activation of both banks simultaneously. Also the noise

generated during sensing of each bank of SDRAM is high

PRELIMINARY (February, 2007, Version 0.1)

11

AMIC Technology, Corp.

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