AT25DF321A-SH-T Atmel, AT25DF321A-SH-T Datasheet - Page 25

• Manufacturer Part Number: AT25DF321A-SH-T
• Description: IC FLASH 32MBIT 100MHZ 8SOIC
• Manufacturer: Atmel

Specifications of AT25DF321A-SH-T

• Format - Memory: FLASH
• Memory Type: DataFLASH
• Memory Size: 32M (16384 pages x 256 Bytes)
• Speed: 100MHz
• Interface: SPI, RapidS
• Voltage - Supply: 2.7 V ~ 3.6 V
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 8-SOIC (5.3mm Width), 8-SOP, 8-SOEIAJ
• Density: 32Mb
• Access Time (max): 5ns
• Interface Type: Serial (SPI)
• Address Bus: 1b
• Operating Supply Voltage (typ): 3.3V
• Operating Temp Range: -40C to 85C
• Package Type: SOIC
• Program/erase Volt (typ): 2.7 to 3.6V
• Sync/async: Synchronous
• Operating Temperature Classification: Industrial
• Operating Supply Voltage (min): 2.7V
• Operating Supply Voltage (max): 3.6V
• Word Size: 8b
• Number Of Words: 4M
• Supply Current: 19mA
• Mounting: Surface Mount
• Pin Count: 8
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

3686D–DFLASH–12/09
10.
10.1
Security Commands
Sector Lockdown
Certain applications require that portions of the Flash memory array be permanently protected against malicious attempts
at altering program code, data modules, security information, or encryption/decryption algorithms, keys, and routines. To
address these applications, the device incorporates a sector lockdown mechanism that allows any combination of individual
64-Kbyte sectors to be permanently locked so that they become read only. Once a sector is locked down, it can never be
erased or programmed again, and it can never be unlocked from the locked down state.
Each 64-Kbyte physical sector has a corresponding single-bit Sector Lockdown Register that is used to control the
lockdown status of that sector. These registers are nonvolatile and will retain their state even after a device power-cycle or
reset operation. The following table outlines the two states of the Sector Lockdown Registers.
Table 10-1.
Issuing the Sector Lockdown command to a particular sector address will set the corresponding Sector Lockdown Register
to the logical “1” state. Each Sector Lockdown Register can only be set once; therefore, once set to the logical “1” state,
a Sector Lockdown Register cannot be reset back to the logical “0” state.
Before the Sector Lockdown command can be issued, the Write Enable command must have been previously issued to set
the WEL bit in the Status Register to a logical “1”. In addition, the Sector Lockdown Enabled (SLE) bit in the Status
Register must have also been previously set to the logical “1” state by using the Write Status Register Byte 2 command
(see
and the opcode of 33h must be clocked into the device followed by three address bytes designating any address within
the 64-Kbyte sector to be locked down. After the three address bytes have been clocked in, a confirmation byte of D0h
must also be clocked in immediately following the three address bytes. Any additional data clocked into the device after the
first byte of data will be ignored. When the CS pin is deasserted, the Sector Lockdown Register corresponding to the sector
addressed by A23-A0 will be set to the logical “1” state, and the sector itself will then be permanently locked down from
program and erase operations within a time of t
logical “0” state.
The complete three address bytes and the correct confirmation byte value of D0h must be clocked into the device before
the CS pin is deasserted, and the CS pin must be deasserted on an even byte boundary (multiples of eight bits);
otherwise, the device will abort the operation. When the device aborts the Sector Lockdown operation, the state of the
corresponding Sector Lockdown Register as well as the SLE bit in the Status Register will be unchanged; however, the
WEL bit in the Status Register will be reset to a logical “0”.
As a safeguard against accidental or erroneous locking down of sectors, the Sector Lockdown command can be enabled
and disabled as needed by using the SLE bit in the Status Register. In addition, the current sector lockdown state can be
frozen so that no further modifications to the Sector Lockdown Registers can be made (see
below). If the Sector Lockdown command is disabled or if the sector lockdown state is frozen, then any attempts to issue
the Sector Lockdown command will be ignored, and the device will reset the WEL bit in the Status Register back to a
logical “0” and return to the idle state once the CS pin has been deasserted.
Value
0
1
“Write Status Register Byte 2” on page 35
Sector Lockdown Status
Sector is not locked down and can be programmed and erased. This is the default state.
Sector is permanently locked down and can never be programmed or erased again
Sector Lockdown Register Values
). To issue the Sector Lockdown command, the CS pin must first be asserted
LOCK
. In addition, the WEL bit in the Status Register will be reset back to the
“Freeze Sector Lockdown State”
Atmel AT25DF321A
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