V54C365164VC datasheet(8/54 Pages) MOSEL

8 / 54 page

MOSEL VITELIC

V54C365164VC

V54C365164VC Rev. 0.8 July 2001

Burst Length and Sequence:

Refresh Mode

SDRAM has two refresh modes, Auto Refresh

and Self Refresh. Auto Refresh is similar to the CAS

-before-RAS refresh of conventional DRAMs. All of

banks must be precharged before applying any re-

fresh mode. An on-chip address counter increments

the word and the bank addresses and no bank infor-

mation is required for both refresh modes.

The chip enters the Auto Refresh mode, when

RAS and CAS are held low and CKE and WE are

held high at a clock timing. The mode restores word

line after the refresh and no external precharge

command is necessary. A minimum tRC time is re-

quired between two automatic refreshes in a burst

refresh mode. The same rule applies to any access

command after the automatic refresh operation.

The chip has an on-chip timer and the Self Re-

fresh mode is available. It enters the mode when

RAS, CAS, and CKE are low and WE is high at a

clock timing. All of external control signals including

the clock are disabled. Returning CKE to high en-

ables the clock and initiates the refresh exit opera-

tion. After the exit command, at least one tRC delay

is required prior to any access command.

DQM Function

DQM has two functions for data I/O read and

write operations. During reads, when it turns to

“high” at a clock timing, data outputs are disabled

and become high impedance after two clock delay

(DQM Data Disable Latency tDQZ ). It also provides

a data mask function for writes. When DQM is acti-

vated, the write operation at the next clock is prohib-

ited (DQM Write Mask Latency tDQW = zero clocks).

Suspend Mode

During normal access mode, CKE is held high en-

abling the clock. When CKE is low, it freezes the in-

ternal clock and extends data read and write

operations. One clock delay is required for mode

entry and exit (Clock Suspend Latency tCSL).

Power Down

In order to reduce standby power consumption, a

power down mode is available. All banks must be

precharged and the necessary Precharge delay

(trp) must occur before the SDRAM can enter the

Power Down mode. Once the Power Down mode is

initiated by holding CKE low, all of the receiver cir-

cuits except CLK and CKE are gated off. The Power

Down mode does not perform any refresh opera-

tions, therefore the device can’t remain in Power

Down mode longer than the Refresh period (tref) of

the device. Exit from this mode is performed by tak-

ing CKE “high”. One clock delay is required for

mode entry and exit.

Auto Precharge

Two

methods

are

available

precharge

SDRAMs. In an automatic precharge mode, the

CAS timing accepts one extra address, CA10, to

determine whether the chip restores or not after the

Burst

Length

Starting Address

(A2 A1 A0)

Sequential Burst Addressing

(decimal)

Interleave Burst Addressing

(decimal)

xx0

xx1

0, 1

1, 0

0, 1

1, 0

4x00

x01

x10

x11

0, 1, 2, 3

1, 2, 3, 0

2, 3, 0, 1

3, 0, 1, 2

0, 1, 2, 3

1, 0, 3, 2

2, 3, 0, 1

3, 2, 1, 0

000

001

010

011

100

101

110

111

Full

Page

nnn

Cn, Cn+1, Cn+2,.....

not supported

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