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Functional Overview

All synchronous inputs pass through input registers controlled

by the rising edge of the clock. Maximum access delay from

the clock rise (t

) is 6.5 ns (133-MHz device).

CDV

The CY7C1297H supports secondary cache in systems

utilizing either a linear or interleaved burst sequence. The

interleaved burst order supports Pentium and i486™

processors. The linear burst sequence is suited for processors

that utilize a linear burst sequence. The burst order is

user-selectable, and is determined by sampling the MODE

input. Accesses can be initiated with either the Processor

Address Strobe (ADSP) or the Controller Address Strobe

(ADSC). Address advancement through the burst sequence is

controlled by the ADV input. A two-bit on-chip wraparound

burst counter captures the first address in a burst sequence

and automatically increments the address for the rest of the

burst access.

Byte Write operations are qualified with the Byte Write Enable

(BWE) and Byte Write Select (BW

Enable (GW) overrides all byte write inputs and writes data to

all four bytes. All writes are simplified with on-chip

synchronous self-timed write circuitry.

Three synchronous Chip Selects (CE

asynchronous Output Enable (OE) provide for easy bank

selection and output tri-state control. ADSP is ignored if CE

is HIGH.

Single Read Accesses

A single read access is initiated when the following conditions

are satisfied at clock rise: (1) CE

asserted active, and (2) ADSP or ADSC is asserted LOW (if

the access is initiated by ADSC, the write inputs must be

deasserted during this first cycle). The address presented to

the address inputs is latched into the address register and the

burst counter/control logic and presented to the memory core.

If the OE input is asserted LOW, the requested data will be

available at the data outputs a maximum to t

rise. ADSP is ignored if CE

Single Write Accesses Initiated by ADSP

This access is initiated when the following conditions are

satisfied at clock rise: (1) CE

active, and (2) ADSP is asserted LOW. The addresses

presented are loaded into the address register and the burst

inputs (GW, BWE, and BW

[A:B]

clock cycle. If the Write inputs are asserted active (see Write

Cycle Descriptions table for appropriate states that indicate a

Write) on the next clock rise, the appropriate data will be

latched and written into the device. Byte Writes are allowed.

During byte writes, BW

controls DQ

All I/Os are tri-stated during a Byte Write. Since this is a

common I/O device, the asynchronous OE input signal must

be deasserted and the I/Os must be tri-stated prior to the

presentation of data to DQs. As a safety precaution, the data

lines are tri-stated once a Write cycle is detected, regardless

of the state of OE.

Single Write Accesses Initiated by ADSC

This write access is initiated when the following conditions are

satisfied at clock rise: (1) CE

Document #: 38-05669 Rev. *B

) inputs. A Global Write

[A:D]

, CE

) and an

, CE

, and CE

are all

after clock

CDV

is HIGH.

, CE

are all asserted

) are ignored during this first

and BW

controls DQ

, CE

, and CE

are all asserted

active, (2) ADSC is asserted LOW, (3) ADSP is deasserted

HIGH, and (4) the Write input signals (GW, BWE, and BW

indicate a write access. ADSC is ignored if ADSP is active

LOW.

The addresses presented are loaded into the address register

and the burst counter/control logic and delivered to the

memory core. The information presented to DQ

written into the specified address location. Byte Writes are

allowed. During Byte Writes, BW

controls DQ

. All I/Os are tri-stated when a write is detected,

even a Byte Write. Since this is a common I/O device, the

asynchronous OE input signal must be deasserted and the

I/Os must be tri-stated prior to the presentation of data to DQs.

As a safety precaution, the data lines are tri-stated once a

Write cycle is detected, regardless of the state of OE.

Burst Sequences

The CY7C1297H provides an on-chip two-bit wraparound burst

counter inside the SRAM. The burst counter is fed by A

and can follow either a linear or interleaved burst order. The

burst order is determined by the state of the MODE input. A

LOW on MODE will select a linear burst sequence. A HIGH on

MODE will select an interleaved burst order. Leaving MODE

unconnected will cause the device to default to a interleaved

burst sequence.

Sleep Mode

The ZZ input pin is an asynchronous input. Asserting ZZ

places the SRAM in a power conservation "sleep" mode. Two

clock cycles are required to enter into or exit from this "sleep"

mode. While in this mode, data integrity is guaranteed.

Accesses pending when entering the "sleep" mode are not

considered valid nor is the completion of the operation

guaranteed. The device must be deselected prior to entering

the "sleep" mode. CEs, ADSP, and ADSC must remain

inactive for the duration of t

LOW.

Interleaved Burst Address Table

(MODE = Floating or V

First

Second

Address

A1, A0

Linear Burst Address Table

(MODE = GND)

First

Second

Address

, A

CY7C1297H

[A:B]

controls DQ

and BW

after the ZZ input returns

ZZREC

)

Third

Fourth

Address

A1, A0

Third

Fourth

Address

, A

Page 4 of 15

)

[A:B]

will be

[1:0]

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