128Kx36 & 256Kx18 Synchronous SRAM

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Rev. 3.0 July 2006

K7B401825B

K7B403625B

FUNCTION DESCRIPTION

The K7B403625B and K7B401825B are synchronous SRAM designed to support the burst address accessing sequence of the Pen-

tium and Power PC based microprocessor. All inputs (with the exception of OE, LBO and ZZ) are sampled on rising clock edges. The

start and duration of the burst access is controlled by ADSC, ADSP and ADV and chip select pins.

When ZZ is pulled high, the SRAM will enter a Power Down State. At this time, internal state of the SRAM is preserved. When ZZ

returns to low, the SRAM normally operates after 2cycles of wake up time. ZZ pin is pulled down internally.

Read cycles are initiated with ADSP(or ADSC) using the new external address clocked into the on-chip address register when both

GW and BW are high or when BW is low and WEa, WEb, WEc, and WEd are high. When ADSP is sampled low, the chip selects are

sampled active, and the output buffer is enabled with OE. the data of cell array accessed by the current address are projected to the

output pins.

Write cycles are also initiated with ADSP(or ADSC) and are differentiated into two kinds of operations; All byte write operation and

individual byte write operation.

All byte write occurs by enabling GW(independent of BW and WEx.), and individual byte write is performed only when GW is high

and BW is low. In K7B403625B, a 128Kx36 organization, WEa controls DQa0 ~ DQa7 and DQPa, WEb controls DQb0 ~ DQb7 and

DQPb, WEc controls DQc0 ~ DQc7 and DQPc and WEd controls DQd0 ~ DQd7 and DQPd.

ADV is ignored at the clock edge when ADSP is asserted, but can be sampled on the subsequent clock edges. The address

increases internally for the next access of the burst when ADV is sampled low.

Addresses are generated for the burst access as shown below, The starting point of the burst sequence is provided by the external

address. The burst address counter wraps around to its initial state upon completion. The burst sequence is determined by the state

of the LBO pin. When this pin is Low, linear burst sequence is selected. And this pin is High, Interleaved burst sequence is selected.

BURST SEQUENCE TABLE

(Interleaved Burst)

Note : 1. LBO pin must be tied to high or low, and floating state must not be allowed.

LBO PIN

HIGH

Case 1

Case 2

Case 3

Case 4

First Address

Fourth Address

0

0

1

1

0

1

0

1

0

0

1

1

1

0

1

0

1

1

0

0

0

1

0

1

1

1

0

0

1

0

1

0

BURST SEQUENCE TABLE

(Linear Burst)

Note : 1. LBO pin must be tied to high or low, and floating state must not be allowed.

LBO PIN

LOW

Case 1

Case 2

Case 3

Case 4

First Address

Fourth Address

0

0

1

1

0

1

0

1

0

1

1

0

1

0

1

0

1

1

0

0

0

1

0

1

1

0

0

1

1

0

1

0

ASYNCHRONOUS TRUTH TABLE

OPERATION

ZZ

OE

I/O STATUS

Sleep Mode

H

X

High-Z

Read

LL

DQ

L

H

High-Z

Write

L

X

Din, High-Z

Deselected

L

X

High-Z

Notes

1. X means "Don't Care".

2. ZZ pin is pulled down internally

3. For write cycles that following read cycles, the output buffersmust

be disabled with OE, otherwise data bus contention will occur.

4. Sleep Mode means power down state of which stand-by current

does not depend on cycle time.

5. Deselected means power down state of which stand-by current

depends on cycle time.