m29dw641f STMicroelectronics, m29dw641f Datasheet - Page 73

• Manufacturer Part Number: m29dw641f
• Description: 64 Mbit 4mb X16, Multiple Bank, Boot Block 3v Supply Flash Memory
• Manufacturer: STMicroelectronics

M29DW641F
Appendix D
D.1
D.2
Note:
he High voltage Block Protection can be used to prevent any operation from modifying the
data stored in the memory. The blocks are protected in groups, refer to
Table 28: Block Addresses
and Erase Operations within the protected group fail to change the data.
There are three techniques that can be used to control Block Protection, these are the
Programmer technique, the In-System technique and Temporary Unprotection. Temporary
Unprotection is controlled by the Reset/Block Temporary Unprotection pin, RP; this is
described in the Signal Descriptions section.
To protect the Extended Block issue the Enter Extended Block command and then use
either the Programmer or In-System technique. Once protected issue the Exit Extended
Block command to return to read mode. The Extended Block protection is irreversible, once
protected the protection cannot be undone.
Programmer technique
The Programmer technique uses high (V
cannot be achieved using a standard microprocessor bus, therefore the technique is
recommended only for use in Programming Equipment.
To protect a group of blocks follow the flowchart in
Protect
then all groups can be unprotected at the same time. To unprotect the chip follow
Programmer equipment Chip Unprotect
Operations, 8-bit or 16-bit
The timing on these flowcharts is critical. Care should be taken to ensure that, where a
pause is specified, it is followed as closely as possible. Do not abort the procedure before
reaching the end. Chip Unprotect can take several seconds and a user message should be
provided to show that the operation is progressing.
In-system technique
The In-System technique requires a high voltage level on the Reset/Blocks Temporary
Unprotect pin, RP
components on the microprocessor bus, therefore this technique is suitable for use after the
memory has been fitted to the system.
To protect a group of blocks follow the flowchart in
Protect
then all the groups can be unprotected at the same time. To unprotect the chip follow
Figure 25: In-System equipment Chip Unprotect
The timing on these flowcharts is critical. Care should be taken to ensure that, where a
pause is specified, it is followed as closely as possible. Do not allow the microprocessor to
service interrupts that will upset the timing and do not abort the procedure before reaching
the end. Chip Unprotect can take several seconds and a user message should be provided
to show that the operation is progressing.
RP can be either at V
Extended Block.
flowchart. To unprotect the whole chip it is necessary to protect all of the groups first,
flowchart. To unprotect the whole chip it is necessary to protect all of the groups first,
High voltage Block Protection
(1)
. This can be achieved without violating the maximum ratings of the
IH
or at V
mode, gives a summary of each operation.
for details of the Protection Groups. Once protected, Program
ID
when using the In-System Technique to protect the
flowchart.
ID
) voltage levels on some of the bus pins. These
flowchart.
Figure 22: Programmer equipment Group
Figure 36: Programmer technique Bus
Figure 24: In-System equipment Group
High voltage Block Protection
Appendix
Figure 23:
A,
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