M29W640GT70NA6F NUMONYX, M29W640GT70NA6F Datasheet - Page 80

• Manufacturer Part Number: M29W640GT70NA6F
• Description: 64MB FLASH MEMORY
• Manufacturer: NUMONYX

Extended memory block
Appendix C
C.1
C.2
80/91
The M29W640G 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 memory block verify code
operations, BYTE = VIL
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 the
Enter Extended Block command
Table 10
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:
Once the extended block is programmed and protected, the Exit Extended Block command
must be issued to exit the extended block mode and return the device to read mode.
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
In-system technique
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 to10,
and to the corresponding flowcharts,
explanation of the technique).
and
Extended memory block
Table 11: Commands, 8-bit mode, BYTE =
and
and to the corresponding flowcharts,
Table 8: Bus operations, BYTE =
and
M29W640GH, M29W640GL, M29W640GT, M29W640GB
Section 4.3.2: Exit Extended Block
Figure 25
Table 36: Extended block address and
and
Section D.1: Programmer technique
VIL.
Figure
IH
or at V
VIH, for details of how to read
Figure 27
26, for a detailed
ID
(refer
’
in
Table 7: Bus
command, and to
and
Section 4.3.1:
to10 Section D.2:
Figure
28, for