4 block erase – Rainbow Electronics AT25DQ321 User Manual
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AT25DQ321 [DATASHEET]
8718D–DFLASH–12/2012
8.4
Block Erase
A block of 4, 32, or 64 KB can be erased (all bits set to the Logical 1 state) in a single operation by using one of three
different opcodes for the Block Erase command. An opcode of 20h is used for a 4KB erase, an opcode of 52h is used for
a 32KB erase and an opcode of D8h is used for a 64KB erase. Before a Block Erase command can be started, the Write
Enable command must have been previously issued to the device to set the WEL bit of the Status Register to a Logical 1
state.
To perform a Block Erase, the CS pin must first be asserted and the appropriate opcode (20h, 52h, or D8h) must be
clocked into the device. After the opcode has been clocked in, the three address bytes specifying an address within the
4KB, 32KB, or 64KB block to be erased must be clocked in. Any additional data clocked into the device will be ignored.
When the CS pin is deasserted, the device will erase the appropriate block. The erasing of the block is internally
self-timed and should take place in a time of t
BLKE
.
Since the Block Erase command erases a region of bytes, the lower order address bits do not need to be decoded by the
device. Therefore, for a 4KB erase, address bits A11-A0 will be ignored by the device and their values can be either a
Logical 1 or 0. For a 32KB erase, address bits A14-A0 will be ignored and for a 64KB erase, address bits A15-A0 will be
ignored by the device. Despite the lower order address bits not being decoded by the device, the complete three address
bytes must still be clocked into the device before the CS pin is deasserted and the CS pin must be deasserted on a byte
boundary (multiples of eight bits); otherwise, the device will abort the operation and no erase operation will be performed.
If the address specified by A23-A0 points to a memory location within a sector that is in the protected or locked down
state, then the Block Erase command will not be executed and the device will return to the idle state once the CS pin has
been deasserted.
The WEL bit in the Status Register will be reset back to the Logical 0 state if the erase cycle aborts due to an incomplete
address being sent, the CS pin being deasserted on non-byte boundaries or because a memory location within the
region to be erased is protected or locked down.
While the device is executing a successful erase cycle, the Status Register can be read and will indicate that the device
is busy. For faster throughput, it is recommended that the Status Register be polled rather than waiting the t
BLKE
time to
determine if the device has finished erasing. At some point before the erase cycle completes, the WEL bit in the Status
Register will be reset back to the Logical 0 state.
The device also incorporates an intelligent erase algorithm that can detect when a byte location fails to erase properly. If
an erase error occurs, it will be indicated by the EPE bit in the Status Register.
Figure 8-7. Block Erase
SO
SI
SCK
CS
MSB
MSB
2
3
1
0
C
C
C
C
C
C
C
C
6
7
5
4
10 11
9
8
12
31
29 30
27 28
26
Opcode
A
A
A
A
A
A
A
A
A
A
A
A
Address Bits A23-A0
High-impedance