m29w400b-100za6tr STMicroelectronics, m29w400b-100za6tr Datasheet - Page 65

• Manufacturer Part Number: m29w400b-100za6tr
• Description: 64 Mbit 8mb X8 Or 4mb X16, Multiple Bank, Boot Block 3v Supply Flash Memory
• Manufacturer: STMicroelectronics

M29DW640F
Appendix C
C.1
C.2
The has an extra block, the Extended Block, that can be accessed using a dedicated
command.
This Extended Block is 128 Words in x16 mode and 256 Bytes in x8 mode. It is used as a
security block (to provide a permanent security identification number) or to store additional
information.
The Extended Block is either Factory Locked or Customer Lockable, its status is indicated
by bit DQ7. This bit is permanently set to either ‘1’ or ‘0’ at the factory and cannot be
changed. When set to ‘1’, it indicates that the device is factory locked and the Extended
Block is protected. When set to ‘0’, it indicates that the device is customer lockable and the
Extended Block is unprotected. Bit DQ7 being permanently locked to either ‘1’ or ‘0’ is
another security feature which ensures that a customer lockable device cannot be used
instead of a factory locked one.
Bit DQ7 is the most significant bit in the Extended Block Verify Code and a specific
procedure must be followed to read it. See “Extended Block Indicator Bit” in
operations, BYTE = VIL
how to read bit DQ7.
The Extended Block can only be accessed when the device is in Extended Block mode. For
details of how the Extended Block mode is entered and exited, refer to
Protection commands
Commands, 16-bit mode, BYTE = VIH
respectively.
Factory Locked Extended Block
In devices where the Extended Block is factory locked, the Security Identification Number is
written to the Extended Block address space (see
data) in the factory. The DQ7 bit is set to ‘1’ and the Extended Block cannot be unprotected.
Customer Lockable Extended Block
A device where the Extended Block is customer lockable is delivered with the DQ7 bit set to
‘0’ and the Extended Block unprotected. It is up to the customer to program and protect the
Extended Block but care must be taken because the protection of the Extended Block is not
reversible.
There are two ways of protecting the Extended Block:
Issue the Enter Extended Block command to place the device in Extended Block mode,
then use the In-System Technique with RP either at V
Figure 22: In-System Equipment Group Protect flowchart
Equipment Chip Unprotect
Issue the Enter Extended Block command to place the device in Extended Block mode,
then use the Programmer Technique (refer to
Equipment Group Protect flowchart
Unprotect
Extended Memory Block
flowchart, for a detailed explanation of the technique).
and
and
Section 4.3.2: Exit Extended Block
Table 5: Bus operations, BYTE =
flowchart, for a detailed explanation of the technique).
and
and
Table 7: Commands, 8-bit mode, BYTE =
Figure 21: Programmer Equipment Chip
Table 31: Extended Block address and
Appendix
IH
D,
or at V
VIH, respectively, for details of
command, and to
and
Figure 20: Programmer
Extended Memory Block
Figure 23: In-System
ID
(refer to
Section 4.3: Block
Table 4: Bus
Appendix
Table 6:
VIL,
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D,