m28w640fcb STMicroelectronics, m28w640fcb Datasheet - Page 21

• Manufacturer Part Number: m28w640fcb
• Description: 64 Mbit 4mb X16, Boot Block 3v Supply Flash Memory
• Manufacturer: STMicroelectronics

M28W640FCT, M28W640FCB
4.13
Block Lock command
The Block Lock command is used to lock a block and prevent Program or Erase operations
from changing the data in it. All blocks are locked at power-up or reset.
Two Bus Write cycles are required to issue the Block Lock command.
The lock status can be monitored for each block using the Read Electronic Signature
command.
The Block Lock bits are volatile, once set they remain set until a hardware reset or power-
down/power-up. They are cleared by a Blocks Unlock command. Refer to the section, Block
Locking, for a detailed explanation.
The first bus cycle sets up the Block Lock command.
The second Bus Write cycle latches the block address.
Table 10
shows the protection status after issuing a Block Lock command.
Command interface
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