3597H–DFLASH–02/07

AT45DB321D [Preliminary]

9.1.2 Program Sector Protection Register Command

Once the Sector Protection Register has been erased, it can be reprogrammed using the Pro-

gram Sector Protection Register command.

To program the Sector Protection Register, the CS

pin must first be asserted and the appropri-

ate 4-byte opcode sequence must be clocked into the device via the SI pin. The 4-byte opcode

sequence must start with 3DH and be followed by 2AH, 7FH, and FCH. After the last bit of the

opcode sequence has been clocked into the device, the data for the contents of the Sector Pro-

tection Register must be clocked in. As described in Section 9.1, the Sector Protection Register

contains 64 bytes of data, so 64 bytes must be clocked into the device. The first byte of data cor-

responds to sector 0, the second byte corresponds to sector 1, and so on with the last byte of

data corresponding to sector 63.

After the last data byte has been clocked in, the CS

pin must be deasserted to initiate the inter-

nally self-timed program cycle. The programming of the Sector Protection Register should take

place in a time of t

, during which time the Status Register will indicate that the device is busy. If

the device is powered-down during the program cycle, then the contents of the Sector Protection

If the proper number of data bytes is not clocked in before the CS

pin is deasserted, then the

protection status of the sectors corresponding to the bytes not clocked in can not be guaranteed.

For example, if only the first two bytes are clocked in instead of the complete 62 bytes, then the

protection status of the last 62 sectors cannot be guaranteed. Furthermore, if more than

64 bytes of data is clocked into the device, then the data will wrap back around to the beginning

of the register. For instance, if 65 bytes of data are clocked in, then the 65th byte will be stored at

byte location 0 of the Sector Protection Register.

If a value other than 00H or FFH is clocked into a byte location of the Sector Protection Register,

then the protection status of the sector corresponding to that byte location cannot be guaran-

teed. For example, if a value of 17H is clocked into byte location 2 of the Sector Protection

The Sector Protection Register can be reprogrammed while the sector protection enabled or dis-

abled. Being able to reprogram the Sector Protection Register with the sector protection enabled

allows the user to temporarily disable the sector protection to an individual sector rather than dis-

abling sector protection completely.

The Program Sector Protection Register command utilizes the internal SRAM buffer 1 for pro-

cessing. Therefore, the contents of the buffer 1 will be altered from its previous state when this

command is issued.

Figure 9-3. Program Sector Protection Register

Command Byte 1 Byte 2 Byte 3 Byte 4

Program Sector Protection Register 3DH 2AH 7FH FCH

Data Byte

Opcode

Byte 1

Opcode

Byte 2

Opcode

Byte 3

Opcode

Byte 4

Data Byte

n + 1

Data Byte

n + 63

Each transition

represents 8 bits

3597H–DFLASH–02/07

AT45DB321D [Preliminary]

9.1.3 Read Sector Protection Register Command

To read the Sector Protection Register, the CS

pin must first be asserted. Once the CS pin has

been asserted, an opcode of 32H and 3 dummy bytes must be clocked in via the SI pin. After the

last bit of the opcode and dummy bytes have been clocked in, any additional clock pulses on the

SCK pins will result in data for the content of the Sector Protection Register being output on the

SO pin. The first byte corresponds to sector 0 (0a, 0b), the second byte corresponds to sector 1

and the last byte (byte 64) corresponds to sector 63. Once the last byte of the Sector Protection

output on the SO pin. The CS

must be deasserted to terminate the Read Sector Protection Reg-

ister operation and put the output into a high-impedance state.

Note: xx = Dummy Byte

Figure 9-4. Read Sector Protection Register

9.1.4 Various Aspects About the Sector Protection Register

The Sector Protection Register is subject to a limit of 10,000 erase/program cycles. Users are

encouraged to carefully evaluate the number of times the Sector Protection Register will be

modified during the course of the applications’ life cycle. If the application requires that the Sec-

tor Protection Register be modified more than the specified limit of 10,000 cycles because the

application needs to temporarily unprotect individual sectors (sector protection remains enabled

while the Sector Protection Register is reprogrammed), then the application will need to limit this

practice. Instead, a combination of temporarily unprotecting individual sectors along with dis-

abling sector protection completely will need to be implemented by the application to ensure that

the limit of 10,000 cycles is not exceeded.

Command Byte 1 Byte 2 Byte 3 Byte 4

Read Sector Protection Register 32H xxH xxH xxH

Opcode X X X

Data Byte

n + 1

Data Byte

n + 63

Each transition

represents 8 bits

3597H–DFLASH–02/07

AT45DB321D [Preliminary]

10. Security Features

10.1 Sector Lockdown

The device incorporates a Sector Lockdown mechanism that allows each individual sector to be

permanently locked so that it becomes read only. This is useful for applications that require the

ability to permanently protect a number of sectors against malicious attempts at altering program

code or security information. Once a sector is locked down, it can never be erased or pro-

grammed, and it can never be unlocked.

To issue the Sector Lockdown command, the CS

pin must first be asserted as it would be for

any other command. Once the CS

pin has been asserted, the appropriate 4-byte opcode

sequence must be clocked into the device in the correct order. The 4-byte opcode sequence

must start with 3DH and be followed by 2AH, 7FH, and 30H. After the last byte of the command

sequence has been clocked in, then three address bytes specifying any address within the sec-

tor to be locked down must be clocked into the device. After the last address bit has been

clocked in, the CS

pin must then be deasserted to initiate the internally self-timed lockdown

sequence.

The lockdown sequence should take place in a maximum time of t

, during which time the Status

tion of the lockdown sequence, then the lockdown status of the sector cannot be guaranteed. In

this case, it is recommended that the user read the Sector Lockdown Register to determine the

status of the appropriate sector lockdown bits or bytes and reissue the Sector Lockdown com-

mand if necessary.

Figure 10-1. Sector Lockdown

Command Byte 1 Byte 2 Byte 3 Byte 4

Sector Lockdown 3DH 2AH 7FH 30H

Opcode

Byte 1

Opcode

Byte 2

Opcode

Byte 3

Opcode

Byte 4

Address

Bytes

Address

Bytes

Address

Bytes

Each transition

represents 8 bits

Part #	AT45DB321D-MU
Description	FLASH, 32MB, DFN-8, Memory Size:32Mbit, Flash Memory Confi
Category	IC
Availability	Out of Stock
Qty	0

AT45DB321D-MU

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