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LH28F040SUT-Z4

4M (512K × 8) Flash Memory

Sharp Electronics 

4M (512K × 8) Flash Memory

LH28F040SUTD-Z4

4M DUAL WORK FLASH MEMORY

SOFTWARE ALGORITHMS

Overview

With the advanced Command User Interface, its Per-

formance Enhancement commands and Status Regis-

ters, the software code required to perform a given

operation may become more intensive but it will result

in much higher write/erase performance compared with

current flash memory architectures.

The software flowcharts describing how a given

operation proceeds are shown here. Figures 4 through

6 depict flowcharts using the 2nd generation flash

device in the LH28F008SA-compatible mode. Figures

7 through 12 depict flowcharts using the 2nd genera-

tion flash device’s performance enhancement com-

mands mode.

When the device power-up or reset is completed, Set

Write Protect command must be written to both the bank

selected by BE 0» and BE 1» in order to reflect actual block

lock status.

When the device power-up or reset is completed, all

blocks come up locked. Therefore, Byte Write, Two Byte

Serial Write and Block Erase can not be performed in

each block. However, at that time, Erase All Unlocked

Block is performed normally, if used, and reflect actual

lock status, also the unlocked block data is erased. When

the device power-up or reset is completed, Set Write

Protect command must be written to reflect actual block

lock status.

Reset Write Protect command must be written be-

fore Write Block Lock command. To reflect actual block

lock status, Set Write Protect command is succeeded.

The Compatible Status Register (CSR) used to

determine which blocks are locked. In order to see Lock

Status of certain block, a Byte Write command (WA =

Block Address, WD = FHH) is written to the CUI, after

issuing Set Write Protect command. If CSR.7, CSR.5

and CSR.4 (WSMS, ES and DWS) are set to ‘1’s, the

block is locked. If CSR.7 is set to ‘1’, the block is not

locked.

Reset Write Protect command enables Write/Erase

operation to each block.

In the case of Block Erase is performed, the block

lock information is also erased. Block Lock command

and Set Write Protect command must be written to pro-

hibit Write/Erase operation to each block.

There are unassigned commands. It is not recom-

mended that the customer use any command other than

the valid commands specified in “Command Bus Defi-

nitions”. Sharp reserved the right to redefine these codes

for future functions.

9

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