MT28F004B3 View Datasheet(PDF) - Micron Technology

Part Name

Description

Manufacturer

MT28F004B3

FLASH MEMORY

Micron Technology 

4Mb

SMART 3 BOOT BLOCK FLASH MEMORY

FUNCTIONAL DESCRIPTION

The MT28F004B3 and MT28F400B3 Flash devices in-

corporate a number of features ideally suited for system

firmware. The memory array is segmented into indi-

vidual erase blocks. Each block may be erased without

affecting data stored in other blocks. These memory

blocks are read, written and erased with commands to

the command execution logic (CEL). The CEL controls

the operation of the internal state machine (ISM), which

completely controls all WRITE, BLOCK ERASE and VERIFY

operations. The ISM protects each memory location from

over-erasure and optimizes each memory location for

maximum data retention. In addition, the ISM greatly

simplifies the control necessary for writing the device in-

system or in an external programmer.

The Functional Description provides detailed infor-

mation on the operation of the MT28F004B3 and

MT28F400B3 and is organized into these sections:

• Overview

• Memory Architecture

• Output (READ) Operations

• Input Operations

• Command Set

• ISM Status Register

• Command Execution

• Error Handling

• WRITE/ERASE Cycle Endurance

• Power Usage

• Power-Up

OVERVIEW

SMART 3 TECHNOLOGY (B3)

Smart 3 technology allows maximum flexibility for in-

system READ, WRITE and ERASE operations. WRITE and

ERASE operations may be executed with a VPP voltage of

3.3V or 5V. Due to process technology advances, 5V VPP is

optimal for application and production programming.

SEVEN INDEPENDENTLY ERASABLE MEMORY

BLOCKS

The MT28F004B3 and MT28F400B3 are organized into

seven independently erasable memory blocks that allow

portions of the memory to be erased without affecting the

rest of the memory data. A special boot block is hard-

ware-protected against inadvertent erasure or writing by

requiring either a super-voltage on the RP# pin or driving

the WP# pin HIGH. One of these two conditions must

exist along with the VPP voltage (3.3V or 5V) on the VPP pin

before a WRITE or ERASE is performed on the boot block.

The remaining blocks require only the VPP voltage be

present on the VPP pin before writing or erasing.

HARDWARE-PROTECTED BOOT BLOCK

This block of the memory array can be erased or

written only when the RP# pin is taken to VHH or when the

WP# pin is brought HIGH. This provides additional secu-

rity for the core firmware during in-system firmware

updates should an unintentional power fluctuation or

system reset occur. The MT28F004B3 and MT28F400B3

are available with the boot block starting at the bottom of

the address space (“B” suffix) or the top of the address

space (“T” suffix).

SELECTABLE BUS SIZE (MT28F400B3 ONLY)

The MT28F400B3 allows selection of an 8-bit

(512K x 8) or 16-bit (256K x 16) data bus for reading and

writing the memory. The BYTE# pin is used to select the

bus width. In the x16 configuration, control data is read

or written only on the lower eight bits (DQ0–DQ7).

Data written to the memory array utilizes all active

data pins for the selected configuration. When the x8

configuration is selected, data is written in byte form;

when the x16 configuration is selected, data is written in

word form.

INTERNAL STATE MACHINE (ISM)

BLOCK ERASE and BYTE/WORD WRITE timing are

simplified with an ISM that controls all erase and write

algorithms in the memory array. The ISM ensures protec-

tion against overerasure and optimizes write margin to

each cell.

During WRITE operations, the ISM automatically in-

crements and monitors WRITE attempts, verifies write

margin on each memory cell and updates the ISM status

register. When BLOCK ERASE is performed, the ISM

automatically overwrites the entire addressed block

(eliminates overerasure), increments and monitors

ERASE attempts, and sets bits in the ISM status register.

ISM STATUS REGISTER

The ISM status register enables an external processor

to monitor the status of the ISM during WRITE and ERASE

operations. Two bits of the 8-bit status register are set and

cleared entirely by the ISM. These bits indicate whether

the ISM is busy with a WRITE or ERASE task and when an

ERASE has been suspended. Additional error informa-

tion is set in three other bits: VPP status, write status and

erase status.

COMMAND EXECUTION LOGIC (CEL)

The CEL receives and interprets commands to the

device. These commands control the operation of the

ISM and the read path (i.e., memory array, ID register or

status register). Commands may be issued to the CEL

while the ISM is active. However, there are restrictions on

4Mb Smart 3 Boot Block Flash Memory

F45_3.p65 – Rev. 3, Pub. 12/01

7

Micron Technology, Inc., reserves the right to change products or specifications without notice.

©2001, Micron Technology, Inc.

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