AT25DF021-SSHF-B Atmel, AT25DF021-SSHF-B Datasheet - Page 18

• Manufacturer Part Number: AT25DF021-SSHF-B
• Description: IC FLASH 2MBIT 70MHZ 8SOIC
• Manufacturer: Atmel

Specifications of AT25DF021-SSHF-B

• Format - Memory: FLASH
• Memory Type: DataFLASH
• Memory Size: 2M (256K x 8)
• Speed: 70MHz
• Interface: SPI, 3-Wire Serial
• Voltage - Supply: 2.3 V ~ 3.6 V
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 8-SOIC (3.9mm Width)
• Memory Configuration: 1024 Pages X 256 Bytes
• Interface Type: Serial, SPI
• Clock Frequency: 66MHz
• Supply Voltage Range: 2.3V To 3.6V
• Memory Case Style: SOIC
• Rohs Compliant: Yes
• Data Bus Width: 8 bit
• Architecture: Sectored
• Timing Type: Synchronous
• Access Time: 6 ns
• Supply Voltage (max): 3.6 V
• Supply Voltage (min): 2.7 V
• Maximum Operating Current: 16 mA
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

9.7
18
Protected States and the Write Protect (WP) Pin
AT25DF021
The WP pin is not linked to the memory array itself and has no direct effect on the protection sta-
tus or lockdown status of the memory array. Instead, the WP pin, in conjunction with the SPRL
(Sector Protection Registers Locked) bit in the Status Register, is used to control the hardware
locking mechanism of the device. For hardware locking to be active, two conditions must be met-
the WP pin must be asserted and the SPRL bit must be in the logical “1” state.
When hardware locking is active, the Sector Protection Registers are locked and the SPRL bit
itself is also locked. Therefore, sectors that are protected will be locked in the protected state,
and sectors that are unprotected will be locked in the unprotected state. These states cannot be
changed as long as hardware locking is active, so the Protect Sector, Unprotect Sector, and
Write Status Register commands will be ignored. In order to modify the protection status of a
sector, the WP pin must first be deasserted, and the SPRL bit in the Status Register must be
reset back to the logical “0” state using the Write Status Register command. When resetting the
SPRL bit back to a logical “0”, it is not possible to perform a Global Protect or Global Unprotect
at the same time since the Sector Protection Registers remain soft-locked until after the Write
Status Register command has been executed.
If the WP pin is permanently connected to GND, then once the SPRL bit is set to a logical “1”,
the only way to reset the bit back to the logical “0” state is to power-cycle the device. This allows
a system to power-up with all sectors software protected but not hardware locked. Therefore,
sectors can be unprotected and protected as needed and then hardware locked at a later time
by simply setting the SPRL bit in the Status Register.
When the WP pin is deasserted, or if the WP pin is permanently connected to V
in the Status Register can still be set to a logical “1” to lock the Sector Protection Registers. This
provides a software locking ability to prevent erroneous Protect Sector or Unprotect Sector com-
mands from being processed. When changing the SPRL bit to a logical “1” from a logical “0”, it is
also possible to perform a Global Protect or Global Unprotect at the same time by writing the
appropriate values into bits 5, 4, 3, and 2 of the first byte of the Status Register.
Tables
Table 9-4.
Note:
(Don't Care)
9-4
1. “n” represents a sector number
WP
X
and
Sector Protection Register States
9-5
detail the various protection and locking states of the device.
Sector Protection Register
n
0
1
(1)
Unprotected
3677D–DFLASH–04/09
CC
Protected
Sector
, the SPRL bit
n
(1)