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AS7C25512FT32A

AS7C25512FT36A

12/23/04, v. 1.2

Alliance Semiconductor

4 of 19

Functional description

The AS7C25512FT32A/36A is a high-performance CMOS 16-Mbit synchronous Static Random Access Memory (SRAM) device organized

as 524,288 words x 32/36.

expansion. Burst operation is initiated in one of two ways: the controller address strobe (ADSC), or the processor address strobe (ADSP). The

burst advance pin (ADV) allows subsequent internally generated burst addresses.

Read cycles are initiated with ADSP (regardless of WE and ADSC) using the new external address clocked into the on-chip address register

when ADSP is sampled LOW, the chip enables are sampled active, and the output buffer is enabled with OE. In a read operation, the data

accessed by the current address registered in the address registers by the positive edge of CLK are carried to the data-out buffer. ADV is

ignored on the clock edge that samples ADSP asserted, but is sampled on all subsequent clock edges. Address is incremented internally for

the next access of the burst when ADV is sampled LOW and both address strobes are HIGH. Burst mode is selectable with the LBO input.

With LBO unconnected or driven HIGH, burst operations use an interleaved count sequence. With LBO driven LOW, the device uses a linear

count sequence.

Write cycles are performed by disabling the output buffers with OE and asserting a write command. A global write enable GWE writes all 32/

36 regardless of the state of individual BW[a:d] inputs. Alternately, when GWE is HIGH, one or more bytes may be written by asserting

BWE and the appropriate individual byte BWn signals.

BWn is ignored on the clock edge that samples ADSP LOW, but it is sampled on all subsequent clock edges. Output buffers are disabled

when BWn is sampled LOW regardless of OE. Data is clocked into the data input register when BWn is sampled LOW. Address is

incremented internally to the next burst address if BWn and ADV are sampled LOW.

Read or write cycles may also be initiated with ADSC instead of ADSP. The differences between cycles initiated with ADSC and ADSP are

as follows:

• ADSP must be sampled HIGH when ADSC is sampled LOW to initiate a cycle with ADSC.

•WE signals are sampled on the clock edge that samples ADSC LOW (and ADSP HIGH).

• Master chip enable CE0 blocks ADSP, but not ADSC.

The AS7C25512FT32A/36A family operates from a core 2.5V power supply. These devices are available in a 100-pin TQFP package.

TQFP capacitance

* Guaranteed not tested

TQFP thermal resistance

Parameter

Symbol

Test conditions

Min

Max

Unit

Input capacitance

-

5

pF

I/O capacitance

-

7

pF

Description

Conditions

Symbol

Typical

Units

Thermal resistance

1 This parameter is sampled

Test conditions follow standard test methods

and procedures for measuring thermal

impedance, per EIA/JESD51

1–layer

40

°C/W

4–layer

22

°C/W

Thermal resistance

8

°C/W