ERASE

The Erase command erases a single block The Erase com-

mand is followed by a single byte telling which block to

erase In this manner no Set-Address sequence is required

to erase a block Following the block address byte is a sin-

gle byte security code 55H that is used to prevent inadver-

tent erasure Get-Status may be used to check if the opera-

tion was completed successfully At the completion of the

Erase command the selected address is undetermined A

Set-Address command is required before any subsequent

Read or Write

DATA-SHIFT-IN

The Data-Shift-In command is used to send data into the

on-chip buffer The number of bits sent into the buffer is

determined by an 8-bit argument following the command

The argument is always 1 less than the actual number of

bits to shift in For example to shift in all 32 bytes (256 bits)

the argument would be FFH (255) To shift in just 4 bytes

(32 bits) the argument would be 1FH (31) Following the

argument the data is shifted in through DI Data-Shift-In

may come before or after the Set-Address sequence when

performing a page write operation

DATA-SHIFT-OUT

The Data-Shift-Out command is used to shift data out of the

on-chip buffer through DO The number of bits sent out is

determined by an 8-bit argument following the command

The argument is always 1 less than the actual number of

bits to shift out For example to shift out all 32 bytes (256

bits) the argument would be FFH (255) To shift out 2 bytes

(16 bits) the argument would be 0FH (15) Following the

argument the data is shifted out through DO Data shifted

out during this command is also internally shifted back into

the data register Thus after shifting all 256 bits the con-

tents of the data register remain unchanged

WRITE ENABLE

The Write Enable command is used as a security check

against inadvertent writes or erases to the device When

this command is issued any subsequent Write or Erase

commands proceed in the normal fashion If the Write En-

able command is not given or the device is in the Write

Disable mode then a write to any page or erase to any block

will not be allowed Use the Get-Status command to deter-

mine whether the device currently is in the Write Enabled or

Disabled mode The NM29A040080 will always power up

in the Write Disable mode This command may be issued

while the device is busy Any change in the Write Enable

status will affect the next write or erase operation that is

issued

WRITE DISABLE

The Write Disable command is used to prevent inadvertant

writes or erases Once this command is executed all subse-

quent Write or Erase commands will not be accepted This

command may be issued while the device is busy Any

change in the Write Enable status will affect the next write

or erase operation that is issued

READ LAST BLOCK

The Read Last Block command is used to read the contents

of Block 127 (4-Mbit) or Block 254 (8-Mbit) The Read Last

Block operation proceeds like a normal read operation ex-

cept that the block number is ignored in the Set-Address

sequence The block address is automatically set to Block

127 or 254 The Set-Address command is still necessary to

set the page to be read In the case of the 8M the page

address can range from 0 – 255 for purposes of reading or

writing the last block

WRITE LAST BLOCK

The Write Last Block command writes a page of data to the

currently selected page of Block 127 or 254 The Write Last

Block command operates like a normal write command ex-

cept the block number is ignored in the Set-Address se-

quence The block address is automatically set to Block 127

or 254 The Set-Address command is still necessary to set

the page to be written In the case of the 8M the page

address can range from 0 – 255 for purposes of reading or

writing the last block The Write Last Block command is

followed by a security code (55H) Once the information has

been written into the memory array it may not be erased

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