M29W640FB STMICROELECTRONICS [STMicroelectronics], M29W640FB Datasheet - Page 26

• Manufacturer Part Number: M29W640FB
• Description: 64 Mbit (8Mb x8 or 4Mb x16, Page, Boot Block) 3V Supply Flash Memory
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

4 Command Interface
4.3
4.3.1
4.3.2
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Block Protection commands
Exit Extended Block command
Enter Extended Block command
The device has an extra 256 Byte block (Extended Block) that can only be accessed using the
Enter Extended Block command. Three Bus write cycles are required to issue the Extended
Block command. Once the command has been issued the device enters Extended Block mode
where all Bus Read or Write operations to the Boot Block addresses access the Extended
Block. The Extended Block (with the same address as the Boot Blocks) cannot be erased, and
can be treated as one-time programmable (OTP) memory. In Extended Block mode the Boot
Blocks are not accessible.
To exit from the Extended Block mode the Exit Extended Block command must be issued.
The Extended Block can be protected, however once protected the protection cannot be
undone.
The Exit Extended Block command is used to exit from the Extended Block mode and return
the device to Read mode. Four Bus Write operations are required to issue the command.
M29W640FT, M29W640FB