AM29F016B datasheet(8/38 Pages) AMD

8 / 38 page

Am29F016B

P R E L I M I NARY

DEVICE BUS OPERATIONS

This section describes the requirements and use of the

device bus operations, which are initiated through the

internal command register. The command register it-

self does not occupy any addressable memory loca-

tion. The register is composed of latches that store the

commands, along with the address and data informa-

tion needed to execute the command. The contents of

the register serve as inputs to the internal state ma-

chine. The state machine outputs dictate the function of

the device. The appropriate device bus operations

table lists the inputs and control levels required, and the

resulting output. The following subsections describe

each of these operations in further detail.

Table 1.

Am29F016B Device Bus Operations

Legend:

L = Logic Low = VIL, H = Logic High = VIH, VID = 12.0 ± 0.5 V, X = Don’t Care, DIN = Data In, DOUT = Data Out, AIN = Address In

Note:

See the sections on Sector Protection and Temporary Sector Unprotect for more information.

Requirements for Reading Array Data

To read array data from the outputs, the system must

drive the CE# and OE# pins to VIL. CE# is the power

control and selects the device. OE# is the output control

and gates array data to the output pins. WE# should re-

main at VIH.

The internal state machine is set for reading array

data upon device power-up, or after a hardware reset.

This ensures that no spurious alteration of the mem-

ory content occurs during the power transition. No

command is necessary in this mode to obtain array

data. Standard microprocessor read cycles that as-

sert valid addresses on the device address inputs

produce valid data on the device data outputs. The

device remains enabled for read access until the

command register contents are altered.

See “Reading Array Data” for more information. Refer

to the AC Read Operations table for timing specifica-

tions and to the Read Operations Timings diagram for

the timing waveforms. ICC1 in the DC Characteristics

table represents the active current specification for

reading array data.

Writing Commands/Command Sequences

To write a command or command sequence (which in-

cludes programming data to the device and erasing

sectors of memory), the system must drive WE# and

CE# to VIL, and OE# to VIH.

An erase operation can erase one sector, multiple sec-

tors, or the entire device. The Sector Address Tables in-

dicate the address space that each sector occupies. A

“sector address” consists of the address bits required

to uniquely select a sector. See the “Command Defini-

tions” section for details on erasing a sector or the en-

tire chip, or suspending/resuming the erase operation.

After the system writes the autoselect command se-

quence, the device enters the autoselect mode. The

system can then read autoselect codes from the inter-

nal register (which is separate from the memory array)

on DQ7–DQ0. Standard read cycle timings apply in this

mode. Refer to the “Autoselect Mode” and “Autoselect

Command Sequence” sections for more information.

ICC2 in the DC Characteristics table represents the ac-

tive current specification for the write mode. The “AC

Characteristics” section contains timing specification

tables and timing diagrams for write operations.

Operation

CE#

OE#

WE#

RESET#

A0–A20

DQ0–DQ7

Read

AIN

DOUT

Write

AIN

DIN

CMOS Standby

VCC ± 0.5 V

High-Z

TTL Standby

High-Z

Output Disable

High-Z

Hardware Reset

High-Z

Temporary Sector Unprotect

(See Note)

VID

AIN

DIN

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