LH28F008SC-L120 View Datasheet(PDF) - Sharp Electronics

Part Name

Description

Manufacturer

LH28F008SC-L120

Flash Memory 8M (1MB × 8)

Sharp Electronics 

sharp

LHF08CH1

15

4.10 Clear Block Lock-Bits Command

All set block lock-bits are cleared in parallel via the

Clear Block Lock-Bits command. With the master

lock-bit not set, block lock-bits can be cleared using

only the Clear Block Lock-Bits command. If the

master lock-bit is set, clearing block lock-bits requires

both the Clear Block Lock-Bits command and VHH on

the RP# pin. See Table 6 for a summary of hardware

and software write protection options.

Clear block lock-bits operation is executed by a

two-cycle command sequence. A clear block lock-bits

setup is first written. After the command is written, the

device automatically outputs status register data

when read (see Figure 10). The CPU can detect

completion of the clear block lock-bits event by

analyzing the RY/BY# Pin output or status register bit

SR.7.

When the operation is complete, status register bit

SR.5 should be checked. If a clear block lock-bit error

is detected, the status register should be cleared.

The CUI will remain in read status register mode until

another command is issued.

This two-step sequence of set-up followed by

execution ensures that block lock-bits are not

accidentally cleared. An invalid Clear Block Lock-Bits

command sequence will result in status register bits

SR.4 and SR.5 being set to "1". Also, a reliable clear

block lock-bits operation can only occur when

VCC=VCC2/3/4 and VPP=VPPH1/2/3. If a clear block

lock-bits operation is attempted while VPP≤VPPLK,

SR.3 and SR.5 will be set to "1". In the absence of

this high voltage, the block lock-bits content are

protected against alteration. A successful clear block

lock-bits operation requires that the master lock-bit is

not set or, if the master lock-bit is set, that RP#=VHH.

If it is attempted with the master lock-bit set and

RP#=VIH, SR.1 and SR.5 will be set to "1" and the

operation will fail. A clear block lock-bits operation

with VIH<RP#<VHH produce spurious results and

should not be attempted.

If a clear block lock-bits operation is aborted due to

VPP or VCC transitioning out of valid range or RP#

active transition, block lock-bit values are left in an

undetermined state. A repeat of clear block lock-bits

is required to initialize block lock-bit contents to

known values. Once the master lock-bit is set, it

cannot be cleared.

Operation

Block Erase or

Byte Write

Set Block

Lock-Bit

Set Master

Lock-Bit

Clear Block

Lock-Bits

Master

Lock-Bit

X

0

1

X

0

1

Table 6. Write Protection Alternatives

Block

Lock-Bit

RP#

Effect

0

VIH or VHH Block Erase and Byte Write Enabled

1

VIH

Block is Locked. Block Erase and Byte Write Disabled

VHH

Block Lock-Bit Override. Block Erase and Byte Write

Enabled

X

VIH or VHH Set Block Lock-Bit Enabled

X

VIH

Master Lock-Bit is Set. Set Block Lock-Bit Disabled

VHH

Master Lock-Bit Override. Set Block Lock-Bit Enabled

X

VIH

Set Master Lock-Bit Disabled

VHH

Set Master Lock-Bit Enabled

X

VIH or VHH Clear Block Lock-Bits Enabled

X

VIH

Master Lock-Bit is Set. Clear Block Lock-Bits Disabled

VHH

Master Lock-Bit Override. Clear Block Lock-Bits

Enabled

Rev. 1.3

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