Extended memory Block
M29W320ET, M29W320EB
Appendix C Extended memory Block
The M29W320E has an extra block, the Extended Block, that can be accessed using a
dedicated command.
This Extended Block is 32 Kwords in x16 mode and 64 Kbytes 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 memory Block Verify code” in Table 2
and Section Table 3. on page 19, Table 2: Bus operations, BYTE = V and Table 3: Bus
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operations, BYTE = V , respectively, for details of how to read bit DQ7.
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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 Section 4.13: Enter
Extended Block command and Section 4.14: Exit Extended Block command, and to Table 4
and Table 5, Table 4: Commands, 16-bit mode, BYTE = V and Table 5: Commands, 8-bit
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mode, BYTE = V , respectively.
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9.1
9.2
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 Table 28: Extended Block Address and
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 or at V (refer to Appendix D:
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ID
Block Protection, Section D.2: In-system technique and to the corresponding
flowcharts, Figure 21 and Figure 22, for a detailed explanation of the technique).
●
Issue the Enter Extended Block command to place the device in Extended Block mode,
then use the Programmer technique (refer to Appendix D: Block Protection,
Section D.1: Programmer technique and to the corresponding flowcharts, Figure 19
and Figure 20, for a detailed explanation of the technique).
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